Opinion
BAXTER, J.This is a sad case. Bridget B., the plaintiff in the underlying action and real party in interest herein, is infected with the human immunodeficiency virus (HIV), the probable causative agent of acquired immune deficiency syndrome (AIDS). So is her husband, petitioner herein and defendant in the underlying action, John B.
Bridget alleges that John became infected with HIV first, as a result of engaging in unprotected sex with multiple men before and during their marriage, and that he then knowingly or negligently transmitted the virus to her. John, who now has full-blown AIDS, alleges in his answer that Bridget infected him and offers as proof a negative HTV test conducted in connection with his application for life insurance on August 17, 2000, six weeks before Bridget discovered she was infected with HIV.
This factual scenario raises a number of interesting questions: What duty does an HIV-positive individual have to avoid transmitting the virus? What level of awareness should be required before a court imposes a duty of care on an HIV-positive individual to avoid transmission of the virus? What responsibility does the victim have to protect himself or herself against possible infection with the virus? And who infected whom with HIV here? However, this case comes to us at an early stage, before any discovery has been conducted. The issue here is simply the extent to which Bridget may inquire into John’s medical records and sexual conduct in order to confirm or refute her allegations that John knowingly or negligently infected her with HIV.
The proposed discovery treads on important statutory and constitutional privacy rights. To decide what discovery should be permitted, we must *1182balance Bridget’s right to discover relevant evidence against John’s right to privacy. After balancing these interests, the superior court overruled John’s objections and authorized broad discovery into John’s medical records as well as his sexual history over the past 10 years. The Court of Appeal granted John’s petition for writ of mandate to the extent the discovery sought the identities of John’s previous sexual partners and admissions concerning his “lifestyle,” but otherwise denied relief.
We conclude that discovery should be further limited in light of John’s negative HIV test on August 17, 2000, which restricts the window period of possible infection to the six months preceding the negative test. However, Bridget, on remand, may overcome this temporal limitation on discovery by offering some basis to question the accuracy or reliability of John’s negative HIV test. We therefore affirm in part and reverse in part the judgment of the Court of Appeal and remand the matter for further proceedings.
I. The Pleadings
Bridget’s complaint for damages alleges the following:
Plaintiff Bridget B. and defendant John B. met in September 1998 and began dating shortly thereafter. The couple became engaged in late 1999 and were married in July 2000. During this period, John represented to Bridget that he was healthy, disease-free, and monogamous. Indeed, it was John who insisted that the couple stop using condoms during intercourse. Based on John’s representations, Bridget complied with his demand to engage in unprotected sex. In September 2000, however, Bridget began to suffer from exhaustion and high fevers.
On October 1, 2000, Bridget learned that she had tested positive for HIV. She was advised to undergo a second test and to have her husband tested as well. The second test confirmed that Bridget was HIV positive. John, too, was determined to be HFV positive. John’s doctor told Bridget that she had “brought the HIV into the marriage.” The doctor prescribed medications for John that made his viral load virtually undetectable. Bridget, on the other hand, was not offered treatment; she was informed that she had “had the illness for a long time.” Bridget became depressed that she had infected her husband with this deadly disease.
In September 2001, John began telling others that Bridget had infected him with HIV. The next month, after defendant refused to continue his treatment, he became much sicker and developed sores on his face and scalp. Although he was diagnosed with AIDS, he refused all treatments and medications except those that treated the visible signs of the disease.
*1183In November 2001, Bridget began to doubt that she had been the cause of defendant’s infection. John responded by asking whether she was “accusing” him of bringing HIV into their lives and advised “it would not be healthy for their marriage to blame him.” The following month, however, John admitted to Bridget that he had had sexual relations with men before their marriage. The complaint further alleges that John also engaged in sexual relations with men during their marriage and used the Internet to solicit these relationships.
The first cause of action (intentional infliction of emotional distress) alleges in material part that John knew he was HIV positive before he married Bridget and before he engaged in unprotected sexual relations with her, that he infected her with HIV knowingly and intentionally, and that he then falsely accused her of infecting him. It further alleges that Bridget was unaware that John had been unfaithful prior to and during their marriage, which put her at great risk for HIV, AIDS, syphilis, and other sexually transmitted diseases, and that she would not have engaged in unprotected sexual relations with him had she known of his infidelity.
The second cause of action (negligent infliction of emotional distress) alleges that John knew or had a reasonable belief that he had HIV, that he nonetheless engaged in unprotected sex with Bridget, and that his negligence caused her to become infected with HIV.
The third cause of action (fraud) alleges that John falsely represented that he did not have any communicable diseases, including HIV, AIDS, or syphilis; that Bridget engaged in unprotected sexual relations with John in reliance on those representations; and that John thereby infected her with HIV.
The fourth cause of action (negligence) incorporates the foregoing allegations and alleges that John owed Bridget a duty of care to disclose the fact that he was HIV positive, that he breached this duty, and that he thereby infected her with HTV.
John’s answer denied every allegation in the complaint and alleged instead that “[i]f either party transmitted the HIV virus to the other, it was Plaintiff who transmitted the virus to the Defendant.” The answer also asserted Bridget’s comparative fault as a defense in that she had “intimate sexual relations with Defendant without using condoms or any other form of protection against the HIV virus or other sexually transmitted diseases.” In a declaration attached to his motion for summary judgment, John stated that he had been tested for HIV in connection with a life insurance application on August 17, 2000, and was found to be negative. John further alleged that he did not discover he was HIV positive until October 13, 2000.
*1184II. Discovery Proceedings
As relevant here, Bridget’s pretrial discovery included the service of special interrogatories and requests for admission concerning John’s sexual history and his awareness of his HIV infection. Bridget also subpoenaed John’s medical and employment records. John objected to each and every special interrogatory and request for admission and also filed motions to quash the subpoenas duces tecum. After plaintiff filed motions to compel responses to the interrogatories and requests for admission, the parties stipulated to the appointment of a discovery referee to hear the pending discovery motions and to make nonbinding recommendations. The referee recommended that John’s objections be overruled and his motions to quash be denied. The superior court adopted the referee’s recommendations.
John filed the instant petition for writ of mandate. The Court of Appeal issued an order to show cause and granted the petition as to four interrogatories and two requests for admission, but otherwise denied relief in a published opinion. Because the issue before us concerns the permissible scope of discovery propounded by Bridget, we describe with particularity the discovery requests in controversy and John’s objections to them below.
A. The Special Interrogatories
Bridget served special interrogatories that required John to state (1) the name, address, and telephone number of every man with whom he has had sexual relations in the last 10 years; (2) the date of his first sexual encounter with a man; (3) the date of his last sexual encounter with a man; (4) the name, address, and telephone number of every man with whom he has had unprotected sex in the last 10 years; (5) the date on which he first became aware he was HIV positive; (6) the date on which he first became aware he had AIDS; (7) the date on which he first told Bridget that he had engaged in unprotected sex with men; (8) the name, address, and telephone number of every HIV-positive man with whom he has had unprotected sex; (9) the name, address, and telephone number of every man who has AIDS and with whom he has had unprotected sex; (10) the number of sexual encounters with men he had in the five years prior to his relationship with Bridget; (11) the date of his last sexual encounter with a man prior to the date of his engagement to Bridget; (12) the date of every sexual encounter he had with a man between his engagement to Bridget and the wedding; and (13) the number of sexual encounters he has had with men since he first met Bridget.
John objected to each of these interrogatories as burdensome, oppressive, overly broad, and harassing, and claimed that they were an invasion of his right to privacy under the state and federal Constitutions. He also objected to *1185selected interrogatories as violative of the physician-patient privilege (Evid. Code, § 990 et seq.) and Health and Safety Code section 120975. In his responses, John disclosed only that he first discovered he had tested positive for HIV on October 13, 2000.
The Court of Appeal granted John’s petition for writ of mandate as to interrogatories Nos. 1, 4, 8, and 9, which sought the identities of his previous sexual partners, and denied relief as to the rest. Bridget had asserted a need to discover the identities of these sexual partners on the ground that John might have told these persons he had HIV but, as the Court of Appeal observed, she offered “nothing to support the suggestion that John may have disclosed his condition at an undisclosed time to an undisclosed person.”
B. The Requests for Admission
Bridget requested John to admit that (1) he had had unprotected sexual relationships with multiple men in the 10 years prior to meeting Bridget; (2) he never told Bridget before they were married that he had had any sexual relationships with men; (3) he had AIDS prior to the time he first had unprotected sex with Bridget; (4) he knew he had AIDS prior to the time he first had unprotected sex with Bridget; (5) he transmitted AIDS to Bridget; (6) he transmitted HIV to Bridget; (7) he never told Bridget, prior to the time he had unprotected sex with her, that he had had unprotected sexual encounters with men; (8) he knew that his lifestyle prior to the time that he met Bridget put him at risk of acquiring HIV; (9) he never told Bridget, prior to having unprotected sex with her, about his lifestyle of having unprotected sex with men; (10) he continued to have unprotected sexual relationships with men after he was married; (11) prior to his marriage, he hid his sexual relations with men from Bridget; (12) he knew he had a history of having unprotected sexual relations with men that put him at risk of acquiring HIV at the time he accused Bridget of infecting him with HIV; (13) he has AIDS; (14) he knew he had ADDS before he married Bridget; and (15) he hid his sexual relations with men from Bridget before the wedding.
John objected to each of these requests as burdensome, oppressive, overly broad, and harassing, and claimed that they were an invasion of his right to privacy under the state and federal Constitutions. He also objected to selected requests as violative of Health and Safety Code section 120975.
The Court of Appeal granted John’s petition for writ of mandate as to requests Nos. 8 and 9, which referred to his “lifestyle,” but denied relief as to the rest. The Court of Appeal determined that the word “lifestyle” was vague and ambiguous and, to the extent it suggested a sexual orientation, impermissibly intruded into John’s zone of sexual privacy.
*1186C. The Subpoenas of Medical and Employment Records and the Results of HIV Tests
Bridget subpoenaed John’s medical records, seeking the results of any HIV and AIDS tests, medical records concerning HIV and AIDS and treatment for those conditions, medical records concerning any and all sexually transmitted diseases since 1980, and medical records concerning any “treatment” he had received since 1980. Bridget also subpoenaed John’s employment records from Universal Studios, including records “regarding his medical leave and the reasons therefor” and “any disability he was suffering from.”
John filed a motion to quash the subpoenas on the grounds that the subpoenas were not supported by affidavits or declarations as required by Code of Civil Procedure section 1985, subdivision (b) or by good cause; that the records were privileged from discovery under the right to privacy in the state and federal Constitutions; that the records were additionally privileged from discovery under Health and Safety Code section 120975 and Evidence Code sections 994 and 1014; and that the subpoenas constituted harassment.
The referee recommended the motions to quash be denied but limited the discoverable medical records relating to treatment since 1980 to “those regarding treatment received ‘for AIDS or HIV infection.’ ” The superior court adopted the referee’s recommendation, and the Court of Appeal denied relief as to this part of the order.
III. Discussion
John asserts a number of reasons for limiting discovery of his sexual history and HIV status, including his constitutional right to privacy, but we first determine whether the requested discovery comports with statutory requirements. (See Schnabel v. Superior Court (1993) 5 Cal.4th 704, 711 [21 Cal.Rptr.2d 200, 854 P.2d 1117]; Vinson v. Superior Court (1987) 43 Cal.3d 833, 838 [239 Cal.Rptr. 292, 740 P.2d 404].) “ ‘Under the discovery statutes, information is discoverable if it is unprivileged and is either relevant to the subject matter of the action or reasonably calculated to reveal admissible evidence.’ ” (Schnabel, supra, 5 Cal.4th at p. 711.) “Discovery may relate to the claim or defense of the party seeking discovery or of any other party to the action.” (Code Civ. Proc., § 2017.010.) “In reviewing an order of a superior court granting discovery, we recognize at the threshold that ‘the discovery statutes vest a wide discretion in the trial court in granting or denying discovery’ and ‘such exercise [of discretion] may only be disturbed when it can be said that there has been an abuse of discretion.’ ” (Pacific Tel. & Tel. Co. v. Superior Court (1970) 2 Cal.3d 161, 171 [84 Cal.Rptr. 718, 465 P.2d 854].)
*1187The subject matter of this action concerns Bridget’s allegation that John infected her with HIV. The gist of the four causes of action—intentional infliction of emotional distress, negligent infliction of emotional distress, fraud, and negligence—is that John represented to Bridget that he was monogamous and had no sexually transmitted diseases; that John made these representations to convince Bridget to engage in unprotected sex with him; that, contrary to these representations, John had not been monogamous and had knowledge, actual or constructive, that he was HIV positive; that John nonetheless had unprotected sex with Bridget without telling her that he was HIV positive; and that Bridget was unaware that John was HIV positive and had not been monogamous. In his defense, John denies infecting Bridget and asserts that if either party infected the other, Bridget infected him.
In light of these allegations, the special interrogatories and requests for admission at issue are within the statutory limits of discoverability. Bridget seeks to discover whether John has AIDS (request for admission No. 13); whether he infected her with HIV and AIDS (request for admission Nos. 5, 6); when John first became aware that he was HIV positive (special interrogatory No. 5); and when he first discovered that he had developed AIDS (special interrogatory No. 6; request for admission Nos. 3, 4, 14). For her claims concerning infliction of emotional distress, Bridget asked John to admit that he knew his sexual behavior had put him at risk of contracting HIV at the time he accused her of infecting him. (Request for admission No. 12.) To help establish that she had been justifiably ignorant of John’s HIV status, Bridget propounded discovery designed to show that John did not tell her he had previously engaged in unprotected sex with men. (Special interrogatory No. 7; request for admission Nos. 2, 7, 11, 15.) Finally, Bridget sought to establish that John had infected her (and not the other way around) by asking John to admit that he had engaged in unprotected sex with men prior to meeting her and during their courtship, engagement, and marriage and by inquiring into the dates and numbers of these encounters. (Special interrogatory Nos. 2, 3, 10-13; request for admission Nos. 1, 10.)
Having determined that the discovery requests authorized by the Court of Appeal meet the statutory standard of discoverability, we proceed to consider John’s specific objections.
A. Whether Discovery Must Be Limited Because the Torts in the Complaint Require Proof That the Infected Individual Had Actual Knowledge of the Infection
John does not deny he would be liable if he had actual knowledge he was infected with HIV and failed to disclose that fact to Bridget. However, he vigorously denies that he can be held liable if the evidence shows only that *1188he had constructive knowledge he was infected with HIV. He concludes, therefore, that discovery should be limited to those requests aimed at uncovering whether he had actual knowledge that he was infected with HIV. According to John, such knowledge can be established only by a positive HIV test from an accredited laboratory or a medical diagnosis of HIV or AIDS.
John’s proposed limitation on discovery calls into question the scope of the torts alleged in the complaint, principally the fourth cause of action for negligent transmission of HIV. This court has not yet had occasion to consider the tort of negligent transmission of a sexually transmitted disease, but the tort is far from novel. Our sister jurisdictions have long imposed liability on individuals who have harmed others by transmitting communicable diseases. (See, e.g., Berner v. Caldwell (Ala. 1989) 543 So.2d 686, 688 [“For over a century, liability has been imposed on individuals who have transmitted communicable diseases that have harmed others”]; Crowell v. Crowell (1920) 180 N.C. 516 [105 S.E. 206, 208] [“it is a well-settled proposition of law that a person is liable if he negligently exposes another to a contagious or infectious disease”]; see generally 39 Am.Jur.2d (1999) Health, § 99, p. 549 [“The general principle is established that a person who negligently exposes another to an infectious or contagious disease, which such other thereby contracts, is liable in damages”].) In particular, courts throughout the United States have recognized a cause of action for the negligent transmission of sexually transmitted diseases. (E.g., McPherson v. McPherson (1998) 1998 ME 141 [712 A.2d 1043, 1045] [citing cases]; Hamblen v. Davidson (Tenn.Ct.App. 2000) 50 S.W.3d 433, 438 [“all the jurisdictions which have considered the issue”]; Doe v. Johnson (W.D.Mich. 1993) 817 F.Supp. 1382, 1389 [citing cases].) California appellate courts are in accord. (Doe v. Roe (1990) 218 Cal.App.3d 1538, 1543 & fn. 3 [267 Cal.Rptr. 564]; Kathleen K. v. Robert B. (1984) 150 Cal.App.3d 992, 996-997 [198 Cal.Rptr. 273].) We agree with these courts that “[t]o be stricken with disease through another’s negligence is in legal contemplation as it often is in the seriousness of consequences, no different from being struck with an automobile through another’s negligence.” (Billo v. Allegheny Steel Co. (1937) 328 Pa. 97 [195 A. 110, 114].)
To prevail in an action for negligence, the plaintiff must demonstrate that the defendant owed a duty to the plaintiff, that the defendant breached that duty, and that the breach proximately caused the plaintiff’s injuries. (Wiener v. Southcoast Childcare Centers, Inc. (2004) 32 Cal.4th 1138, 1145 [12 Cal.Rptr.3d 615, 88 P.3d 517].)
The existence of a legal duty is a question of law for the court. (Delgado v. Trax Bar & Grill (2005) 36 Cal.4th 224, 237 [30 Cal.Rptr.3d 145, *1189113 P.3d 1159].) “As this court has explained, ‘duty’ is not an immutable fact of nature ‘ “but only an expression of the sum total of those considerations of policy which lead the law to say that the particular plaintiff is entitled to protection.” ’ [Citations.] In California, the general rule is that all persons have a duty ‘ “to use ordinary care to prevent others being injured as the result of their conduct. . . .” ’ (Rowland v. Christian (1968) 69 Cal.2d 108, 112 [70 Cal.Rptr. 97, 443 P.2d 561] (citations omitted); Civ. Code, § 1714.)” (Ballard v. Uribe (1986) 41 Cal.3d 564, 572-573, fn. 6 [224 Cal.Rptr. 664, 715 P.2d 624].) Foreseeability of harm is a “ ‘crucial factor’ ” in determining the existence and scope of that duty. (Delgado, supra, 36 Cal.4th at p. 237.)
John concedes that a person who actually knows he or she is infected with a sexually transmitted disease based on a test from an accredited laboratory or a medical diagnosis has a duty to use ordinary care to see that the disease is not transmitted to others. The foreseeability of harm in such a circumstance is manifest. John also concedes the viability of the tort of negligent transmission of HIV. In his view, though, a duty under this tort exists only when the actor has actual knowledge of being HIV positive; constructive knowledge of the infection is insufficient.
Tellingly, neither John nor our dissenting colleagues have identified a single jurisdiction that has limited liability for negligent transmission of HIV or other sexually transmitted diseases only to those who have actual knowledge they are infected. Our sister states instead impose liability when the actor has knowledge, actual or constructive, of a sexually transmitted disease. (Berner v. Caldwell, supra, 543 So.2d at pp. 689-690 & fn. 4 [applying this standard to the transmission of herpes and noting that the same duty could be imposed for other sexually transmitted diseases, including AIDS]; Meany v. Meany (La. 1994) 639 So.2d 229, 236; McPherson v. McPherson, supra, 712 A.2d at p. 1046; Deuschle v. Jobe (Mo.Ct.App. 2000) 30 S.W.3d 215, 219; M.M.D. v. B.L.G. (Minn.Ct.App. 1991) 467 N.W.2d 645, 647 [liability for negligent transmission of herpes exists where boyfriend had history of genital sores but had not been diagnosed with herpes]; Mussivand v. David (1989) 45 Ohio St.3d 314 [544 N.E.2d 265, 270] [“We find the reasoning of these other jurisdictions persuasive”]; Plaza v. Estate of Wisser (1995) 211 A.D.2d 111 [626 N.Y.S.2d 446, 451-452] [allegations of decedent’s actual and constructive knowledge he was infected with HIV was sufficient to withstand motion to dismiss claims of fraud and negligence]; Hamblen v. Davidson, supra, 50 S.W.3d at p. 439 [noting that “the majority of states who have addressed the issue” extend liability to those with actual or constructive knowledge of the sexually transmitted disease]; Doe v. Johnson, supra, 817 F.Supp. at p. 1391 [liability for negligent transmission of HIV includes those who “knew s/he was suffering symptoms associated with the HTV virus . . . or . . . knew of a prior sex partner who was diagnosed as having the HIV virus”]; accord, 65 C.J.S. (2000) Negligence, § 171, p. 503.)
*1190Extending liability to those who have constructive knowledge of the disease, as these jurisdictions have done, comports with general principles of negligence. Indeed, the “very concept of negligence presupposes that the actor either does foresee an unreasonable risk of injury, or could foresee it if he conducted himself as a reasonably prudent person.” (3 Harper et al., The Law of Torts (2d ed. 1986) § 16.5, p. 397; accord, Prosser & Keeton on Torts (5th ed. 1984) § 32, pp. 182-185; Rest.2d Torts, §§ 289, 290; Nolte, The Spoliation Tort: An Approach to Underlying Principles (1994) 26 St. Mary’s L.J. 351, 380 [“negligence law regularly utilizes the concept of constructive knowledge as the requisite notice”].) Because “ ‘[a]ll persons are required to use ordinary care to prevent others being injured as a result of their conduct’ ” (Rowland v. Christian, supra, 69 Cal.2d at p. 112), this court has repeatedly recognized a cause of action for negligence not only against those who have actual knowledge of unreasonable danger, but also against those who have constructive knowledge of it. (See, e.g., Ortega v. Kmart Corp. (2001) 26 Cal.4th 1200, 1210 [114 Cal.Rptr.2d 470, 36 P.3d 11]; Toland v. Sunland Housing Group, Inc. (1998) 18 Cal.4th 253, 260, fn. 1 [74 Cal.Rptr.2d 878, 955 P.2d 504]; Kentucky Fried Chicken of Cal., Inc. v. Superior Court (1997) 14 Cal.4th 814, 823 [59 Cal.Rptr.2d 756, 927 P.2d 1260]; Garcia v. Superior Court (1990) 50 Cal.3d 728, 735 [268 Cal.Rptr. 779, 789 P.2d 960]; Hasson v. Ford Motor Co. (1982) 32 Cal.3d 388, 407 [185 Cal.Rptr. 654, 650 P.2d 1171].) Neither John nor our dissenting colleagues have pointed to any indication that the Legislature intended a lesser duty to apply to HIV.
Moreover, limiting tort defendants to those who have actual knowledge they are infected with HIV would have perverse effects on the spread of the virus. If only those who have been tested are subject to suit, there may be “an incentive for some persons to avoid diagnosis and treatment in order to avoid knowledge of their own infection.” (Gostin & Hodge, Piercing the Veil of Secrecy in HIV/AIDS and Other Sexually Transmitted Diseases: Theories of Privacy and Disclosure in Partner Notification (1998) Duke J. Gender L. & Pol’y 9, 40.) Extending liability to those with constructive knowledge of the disease, on the other hand, “will provide at least a small incentive to others to use proper diagnostic techniques and to alter behavior and procedures so as to limit the likelihood of HIV transmission.” (Hermann, Torts: Private Lawsuits about AIDS in AIDS and the Law: A Guide for the Public (Dalton & Yale AIDS Law Project edits., 1987) p. 172 (Hermann).) Justice Moreno offers no support for his view that tort liability would have no effect on human behavior in this context.
It must be noted, though, that “constructive knowledge,” which means knowledge “that one using reasonable care or diligence should have, and therefore is attributed by law to a given person” (Black’s Law Dict. (7th ed. 1999) p. 876), encompasses a variety of mental states, ranging from one who *1191is deliberately indifferent in the face of an unjustifiably high risk of harm (see Farmer v. Brennan (1994) 511 U.S. 825, 836-840 [128 L.Ed.2d 811, 114 S.Ct. 1970]) to one who merely should know of a dangerous condition (see Ortega v. Kmart Corp., supra, 26 Cal.4th at pp. 1208-1209). At this early stage, when no facts have yet been developed, the issue is not which of these mental states is required for the tort of negligent transmission of HIV, but what is permissible discovery for a party seeking to prove such a tort. In determining whether the requested discovery satisfies statutory requirements, therefore, we should recognize a duty no broader than is necessary to resolve the current discovery dispute.
In this case, we conclude that the tort of negligent transmission of HIV does not depend solely on actual knowledge of HIV infection and would extend at least to those situations where the actor, under the totality of the circumstances, has reason to know of the infection. Under the reason-to-know standard, “the actor has information from which a person of reasonable intelligence or of the superior intelligence of the actor would infer that the fact in question exists, or that such person would govern his conduct upon the assumption that such fact exists.” (Rest.2d Torts, § 12, subd. 1.) In other words, “the actor has knowledge of facts from which a reasonable man of ordinary intelligence or one of the superior intelligence of the actor would either infer the existence of the fact in question or would regard its existence as so highly probable that his conduct would be predicated upon the assumption that the fact did exist.” (Id., § 12, com. a, p. 20.)1
Imposing liability for the transmission of HIV where the actor knows or has reason to know he or she is HIV positive is consistent with the general principle of California law that “ ‘[a]ll persons are required to use ordinary care to prevent others being injured as the result of their conduct.’ ” (Rowland v. Christian, supra, 69 Cal.2d at p. 112.) “Although it is true that some exceptions have been made to the general principle that a person is liable for injuries caused by his failure to exercise reasonable care in the circumstances, it is clear that in the absence of a statutory provision declaring an exception to the fundamental principle enunciated by section 1714 of the Civil Code, no such exception should be made unless clearly supported by public policy.” (Ibid.; see also Randi W. v. Muroc Joint Unified School Dist. (1997) 14 Cal.4th 1066, 1077 [60 Cal.Rptr.2d 263, 929 P.2d 582] (Randi W).) *1192“Before judicially establishing an exception based on public policy, [we] consider a variety of factors; ‘the major ones are the foreseeability of harm to the plaintiff, the degree of certainty that the plaintiff suffered injury, the closeness of the connection between the defendant’s conduct and the injury suffered, the moral blame attached to the defendant’s conduct, the policy of preventing future harm, the extent of the burden to the defendant and consequences to the community of imposing a duty to exercise care with resulting liability for breach, and the availability, cost, and prevalence of insurance for the risk involved.’ [Citations.]” (Merrill v. Navegar, Inc. (2001) 26 Cal.4th 465, 477 [110 Cal.Rptr.2d 370, 28 P.3d 116].)
An analysis of these factors does not justify a departure from the general rule in this instance. The factor that “ ‘plays a very significant role in this calculus’ ” (Randi W., supra, 14 Cal.4th at p. 1077) is the foreseeability of the particular harm, which (like the reason-to-know standard) is assessed by an objective test. (See id. at pp. 1077-1078.) When the actor has reason to know of the HIV infection—i.e., when there is sufficient information to cause a reasonably intelligent actor to infer he or she is infected with the virus or that infection is so highly probable that his or her conduct would be predicated on that assumption—the potential for harm through sexual transmission of the virus is reasonably foreseeable. As to causation, Bridget has plausibly alleged that John infected her during unprotected sex. (See id. at p. 1078.) Whether John’s conduct is morally blameworthy will depend on the evidence uncovered during discovery, but it is certainly arguable that failing to exercise due care to prevent the transmission of a gravely serious disease of which the actor knows or has reason to know falls in that category. (Ibid.)
Moreover, society has an overriding policy of preventing the spread of sexually transmitted diseases (see Health & Saf. Code, § 120290), especially HIV (see, e.g., Health & Saf. Code, § 120291), which would be enhanced by imposing a duty of care on those who have reason to know they are infected with HIV. The burden of a duty of care on defendants who know or have reason to know of their HIV infection is minimal, and the consequences for the community would be salutary. (Cf. Health & Saf. Code, § 121015, subd. (a) [permitting physicians and surgeons to disclose to “a person reasonably believed to be the spouse, or to a person reasonably believed to be a sexual partner or a person with whom the patient has shared the use of hypodermic needles,. .. that the patient has tested positive on a test to detect HIV infection, except that no physician and surgeon shall disclose any identifying information about the individual believed to be infected”].) Indeed, limiting liability only to those who have actual knowledge they are infected would discourage those who fear they may be infected from getting tested, which would be contrary to the public policy of encouraging testing for and preventing the spread of HIV and thwart the effectiveness of new treatments that depend on early diagnosis of the virus.
*1193In sum, none of the factors above justifies a departure from the general negligence rule imposing a duty on those who have actual or constructive knowledge of a dangerous condition. At the same time, we are mindful that our precedents direct us to consider whether a duty of care exists “ ‘on a case-by-case basis.’ ” (Parsons v. Crown Disposal Co. (1997) 15 Cal.4th 456, 472 [63 Cal.Rptr.2d 291, 936 P.2d 70].) Accordingly, our conclusion that a claim of negligent transmission of HIV lies against those who know or at least have reason to know of the disease must be understood in the context of the allegations in this case, which involves a couple who were engaged and subsequently married; a defendant who falsely represented himself as monogamous and disease-free and insisted the couple stop using condoms; and a plaintiff who agreed to stop using condoms in reliance on those false representations. We need not consider the existence or scope of a duty for persons whose relationship does not extend beyond the sexual encounter itself, whose relationship does not contemplate sexual exclusivity, who have not represented themselves as disease-free, or who have not insisted on having sex without condoms.
The discovery Bridget has requested comports with the reason-to-know standard. Evidence that John engaged in unprotected sex outside the relationship during the relevant period and hid these encounters from Bridget, even if insufficient to establish the requisite knowledge for a negligence claim, might reasonably lead to the discovery of evidence as to John’s awareness of the HIV status of those partners—without even disclosing their identities, contrary to Justice Werdegar’s assumption—and thus may be relevant to whether John knew or had reason to know he was infected with HIV. (Doe v. Johnson, supra, 817 F.Supp. at pp. 1395-1396.) Similarly, evidence that John had symptoms consistent with HIV infection may be insufficiently distinctive to indicate HIV infection by itself but may be relevant to whether John knew or had reason to know he was infected when considered in combination with his alleged history of engaging in unprotected sex outside the relationship.
John fails to consider whether the requested information, even if insufficient to establish the requisite knowledge by itself, may be relevant to the existence of such knowledge or reasonably calculated to lead to evidence on that point. He (like our dissenting colleagues) argues instead that the framework for other sexually transmitted diseases ought not be applied to HIV, but does not offer persuasive bases for distinguishing HIV from the other diseases. After careful analysis of John’s argument, we cannot agree that persons who have reason to know they are infected with HIV, a gravely serious disease with no known cure, should be subject to a lesser duty of care than persons who have reason to know they are infected with other sexually transmitted diseases.
*1194John contends that because carriers of HIV may be asymptomatic, possible symptoms of HIV (other than those distinctively and idiosyncratically associated with the virus, such as Kaposi’s sarcoma), are irrelevant. But merely because “[m]any people who are infected with HIV do not have any symptoms at all for many years”2 does not mean that plaintiffs are barred from discovering whether a particular defendant did have unique or diffuse symptoms and whether those symptoms, singly or in combination with other factors, gave the defendant reason to know he or she was infected with HIV. Many sexually transmitted diseases—such as chlamydia,3 gonorrhea,4 syphilis,5 herpes,6 and human papillomavirus (HPV)7—likewise commonly present asymptomatically at the initial stages or have nonspecific symptoms that can be confused with other, more common diseases. Yet, we have been pointed to no decision that has invoked the possible difficulties of establishing the requisite knowledge of these diseases in some instances as a justification for categorically foreclosing recovery in all cases. To the contrary, courts here and elsewhere have regularly found negligence when the evidence does show the defendant knew or had reason to know of infection with these sexually *1195transmitted diseases. John fails to explain why Bridget should be precluded from discovering whether he harbored such knowledge in this case.8
John also complains that the risk of transmission of HIV in any individual act of intercourse is so low as to make it unreasonable to impose a duty of care on someone who is not actually aware he or she is infected. We disagree. A low risk of transmission is insufficient to relieve the infected individual of a duty where the harm itself is great and the duty of care to prevent that harm is not onerous. (See Bigbee v. Pacific Tel. & Tel. Co. (1983) 34 Cal.3d 49, 57 [192 Cal.Rptr. 857, 665 P.2d 947]; Prosser & Keeton on Torts, supra, § 31, p. 171 [“[a]s the gravity of the possible harm increases, the apparent likelihood of its occurrence need be correspondingly less to generate a duty of precaution”].) The AIDS epidemic was and continues to be one of the most dangerous of the modem era, killing over half a million Americans as of the end of 2003. Despite the introduction of antiretroviral therapy, AIDS remains the fifth leading cause of death among those ages 25 to 44. Sadly, HIV mortality declines have slowed while, at the same time, AIDS diagnoses have risen. (The Henry J. Kaiser Family Foundation, HIV/AIDS Policy Fact Sheet: The HIV/AIDS Epidemic in the United States (Sept. 2005) p. 1 at <http://www.kff.org/hivaids/3029-05.cfm> [as of July 3, 2006].) The medical advances in combating HIV do not relieve infected individuals of their duty to avoid transmitting what remains a very serious disease, nor should the efficacy of those advances necessarily determine what discovery is permissible.
The dissenting opinions’ effort to narrow the duty of care for persons infected with HIV is similarly unconvincing. Justice Moreno contends that the general analytic framework of negligence cannot apply here because HIV infection, unlike other sexually transmitted diseases, is “life-threatening.” *1196(Dis. opn. of Moreno, J., post, at p. 1215.) The premise of his argument suffers from a factual flaw; other sexually transmitted diseases, such as syphilis and HPV, are also life-threatening. Moreover, the gravity of the harm from HIV infection is a justification for imposing a greater duty of care on those who are infected (see Prosser & Keeton on Torts, supra, § 31, p. 171; Rest.2d Torts, § 293, com. c, p. 59)—not, as Justice Moreno would have it, a basis for insulating those infected from responsibility for their conduct in transmitting the virus to others. Justice Moreno is also mistaken in assuming that HIV is “unique” (dis. opn. of Moreno, J., post, at p. 1215) in the opprobrium with which those infected are viewed. (See Note, Liability in Tort for the Sexual Transmission of Disease: Genital Herpes and the Law (1984) 70 Cornell L.Rev. 101, 107-108 [“The social stigma associated with genital heipes prompted one popular news magazine to label the disease the ‘new scarlet letter’ ”].) In any event, Justice Werdegar and Justice Moreno fail at bottom to explain why the distinctions between HIV and other sexually transmitted diseases are so fundamental as to warrant wholesale rejection of ordinary tort principles in this case (cf. Hermann, supra, at p. 158 [in analyzing liability for sexual transmission of HIV, “there is clear precedent in the analogous area of transmission of genital herpes”]) or to identify any court that has summarily absolved infected individuals of any responsibility for negligently infecting an intimate partner with HIV.
Justice Moreno’s contention that the Legislature, by criminalizing the intentional and knowing transmission of HIV, has evinced an intent to limit tort liability only to those individuals who have actual knowledge they are infected misapprehends the respective roles of criminal and tort law. That the Legislature “has not adopted a constructive knowledge standard in statutes criminalizing the transmission of AIDS” hardly “reflects a legislative judgment that a constructive knowledge standard is not appropriate for purposes of imposing [tort] liability for the transmission of HIV.” (Dis. opn. of Moreno, J., post, at pp. 1221-1222.) After all, the Legislature typically intends a lowered standard be required for a civil suit to recover damages than for a prosecution imposing criminal penalties, especially where those penalties are substantial. For example, Health & Safety Code section 120291, which criminalizes the intentional and knowing transmission of HIV through unprotected sexual activity, is punishable by up to eight years in prison—but “conduct that is more, not less, culpable is required for imposition of criminal penalties.” (People v. Simon (1995) 9 Cal.4th 493, 517 [37 Cal.Rptr.2d 278, 886 P.2d 1271].) “In the criminal context, ‘ordinary negligence sufficient for recovery in a civil action will not suffice.’ ” (Williams v. Garcetti (1993) 5 Cal.4th 561, 573 [20 Cal.Rptr.2d 341, 853 P.2d 507].) Thus, the fact the Legislature did not attach criminal penalties to those persons who have reason to know they carry HIV and nonetheless take no steps to avoid infecting others in no way suggests that the Legislature intended to depart *1197from Civil Code section 1714 or from ordinary negligence principles in a civil action for negligent transmission of HTV.9
The dissenting opinions’ suggestion that the duty of individuals infected with HIV not to infect others—and not merely the permissibility of discovery aimed at uncovering their HIV status—has somehow been limited by the enactment of statutes protecting the confidentiality of HIV test results proves far too much, inasmuch as the cause of action under the actual-knowledge standard poses the same threat to the confidentiality of a defendant’s HIV test results as does a cause of action under the reason-to-know standard. Indeed, Justice Moreno acknowledges that even an actual-knowledge standard would permit discovery “directed at whether and when defendant had actual knowledge he was HIV positive.” (Dis. opn. of Moreno, J., post, at p. 1212.) The logical consequence of the dissenting opinions’ reading of the statutory scheme, therefore, would be to eliminate entirely the possibility of tort liability for the knowing or negligent transmission of HIV, even when the discovery the plaintiff eventually seeks does not tread on statutory confidentiality. Had the Legislature intended to abrogate ordinary tort principles to such an extent, one would expect it to have expressed its intent more clearly.10
In any event, it is not necessary to consider here whether a conflict exists between Bridget’s entitlement to discover relevant evidence and Health and *1198Safety Code section 120975, which protects the identity of a person taking an HIV test. As the Court of Appeal found, John waived (or is estopped from invoking) this statutory protection by claiming in his answer that Bridget infected him with HIV and by relying on a negative HIV test in support of his motion for summary judgment. (See Taub, Doctors, AIDS, and Confidentiality in the 1990’s (1994) 27 J. Marshall L.Rev. 331, 335 [“courts have held that patients waived their confidentiality rights with respect to their HIV status by placing their medical condition at issue in litigation”].) Nor need we consider the extent of permissible discovery about the HIV status of third parties, since (as the dissenting opinions concede) the discovery we have authorized does not include identifying information about John’s sexual partners. In response to the dissenting opinions’ concerns about future discovery in this and other cases, we reiterate that we do not (and properly cannot) opine as to the propriety of discovery requests that are not before us.
Finally, Justice Moreno’s fear of a spate of shakedown lawsuits designed to force lucrative settlements or to embarrass a former sexual partner is ill-founded and overblown. Such a risk applies equally to tort actions under an actual knowledge standard. Indeed, the risk inheres in a tort for the transmission of any venereal disease. The fact that no jurisdiction has yet been deluged with such suits persuasively rebuts this concern. Moreover, the use of protective orders, sealing orders, and the identification of parties by their initials as well as the constitutional and statutory limits on discovery will ensure that the burden on the litigants and third parties will be minimized to the extent possible and should assuage the fear that litigation will be used as a bludgeon or will become a media circus.
In sum, we are not persuaded that California should be the first jurisdiction in the country to limit liability for the negligent transmission of HIV only to those who have actual knowledge they are HIV positive.
B. Whether Discovery Must Be Limited Because of John’s Right to Privacy Under the State Constitution
Article I, section 1 of the California Constitution recognizes a number of inalienable rights, including the right to privacy. As we have previously observed, the right of privacy extends to sexual relations (Vinson v. Superior Court, supra, 43 Cal.3d at p. 841) and medical records (Hill v. National Collegiate Athletic Assn. (1994) 7 Cal.4th 1, 41 [26 Cal.Rptr.2d 834, 865 P.2d 633]). Accordingly, a litigant may invoke the constitutional right to privacy as justification for refusing to answer questions that unreasonably intrude on that right. (Britt v. Superior Court (1978) 20 Cal.3d 844, 855 [143 Cal.Rptr. 695, 574 P.2d 766] [associational privacy]; Fults v. Superior Court (1979) 88 Cal.App.3d 899, 903 [152 Cal.Rptr. 210] [sexual privacy].)
*1199The right to privacy, however, is not absolute. In appropriate circumstances, this right must be balanced against other important interests. (Hill v. National Collegiate Athletic Assn., supra, 7 Cal.4th at p. 37.) “On occasion [a party’s] privacy interests may have to give way to [the] opponent’s right to a fair trial. Thus courts must balance the right of civil litigants to discover relevant facts against the privacy interests of persons subject to discovery.” (Vinson v. Superior Court, supra, 43 Cal.3d at p. 842.)
Here, defendant has invoked his constitutional right to privacy as justification for refusing to answer questions concerning his HIV status or his sexual history. Bridget, in turn, has identified not only “the historically important state interest of facilitating the ascertainment of truth in connection with legal proceedings” (In re Lifschutz (1970) 2 Cal.3d 415, 432 [85 Cal.Rptr. 829, 467 P.2d 557]), but also the state’s compelling interest in preventing the spread of AIDS, a communicable and dangerous disease. Penal Code section 12022.85, which provides for a three-year enhancement if the perpetrator of specified felonies knows he or she is HIV positive, and Health and Safety Code section 120291, which makes it a felony to intentionally infect another with HIV, are strong statements by the Legislature that the spread of HTV is a serious public health threat and that its control is of paramount importance. (See generally Cruzan v. Director, Missouri Dept. of Health (1990) 497 U.S. 261, 282 [111 L.Ed.2d 224, 110 S.Ct. 2841] [recognizing the state’s “unqualified interest in the preservation of human life”].)
In balancing these competing concerns, we note at the outset that this is not a case in which a plaintiff seeks discovery to obtain information from a defendant whose HIV status is unknown. Both parties have admitted they are HIV positive, informally and in court filings. John thus has a diminished privacy interest in his HIV status. (Cf. In re Marriage of Bonneau (1998) 294 Ill.App.3d 720 [229 Ill.Dec. 187, 691 N.E.2d 123, 134] [declining to permit discovery of medical records where neither party’s HIV status was alleged].) Moreover, not only does the complaint allege sufficient facts to permit the inference that John infected Bridget with HIV, but John has alleged that Bridget infected him. By thus putting his own medical condition at issue, John has “substantially lowered” his expectation of privacy even further. (Heller v. Norcal Mutual Ins. Co. (1994) 8 Cal.4th 30, 43 [32 Cal.Rptr.2d 200, 876 P.2d 999].) After balancing the competing interests in this case, we are persuaded that Bridget is entitled to discovery concerning John’s sexual history and HIV status.
We emphasize, though, that Bridget is not entitled to discovery without limit. As the Court of Appeal pointed out, even where the plaintiff can establish a compelling state interest in discovery, “ ' “ ‘[precision of [compelled disclosure]’ ” ’ is required so that the right of privacy is not *1200' “ ‘curtailed except to the extent necessitated by the legitimate governmental objective.’ ” ’ ” Thus, where a plaintiff seeks discovery from a defendant concerning sexual matters protected by the constitutional right of privacy, the “intrusion upon sexual privacy may only be done on the basis of ‘ “practical necessity” ’ (Fults v. Superior Court, supra, at pp. 904-905), and ‘the compelled disclosure [must] be narrowly drawn to assure maximum protection of the constitutional interests at stake.’ (Britt v. Superior Court, supra, [20 Cal.3d] at p. 859.)” (Boler v. Superior Court (1987) 201 Cal.App.3d 467, 473-474 [247 Cal.Rptr. 185].)
It is therefore essential to measure the closeness of the fit between the requested discovery and the allegations of the complaint. The theory of Bridget’s complaint is that John became infected with HIV prior to or during their relationship by engaging in unprotected sex with other men, that he knew or had reason to know he was infected before he engaged in unprotected sex with her, that he did not share his knowledge with Bridget or otherwise take steps to prevent transmission of the virus, and that he infected her with HIV during unprotected sex. To prove these allegations, it is necessary for Bridget to inquire into John’s medical records and his sexual activity, as the superior court and the Court of Appeal found.
Not all of the discovery authorized by the superior court and the Court of Appeal satisfies this heightened standard, however. To the extent that special interrogatory Nos. 3 and 13 and request for admission No. 10 seek information concerning John’s sexual conduct after the couple stopped having sex—which, according to the complaint, was sometime during the honeymoon in July 2000—they are overbroad. John’s sexual conduct after the cessation of marital sexual relations could not have resulted in the transmission of HIV to Bridget through sexual relations as alleged in the complaint, nor would it shed light on whether John knew or had reason to know that he was HIV positive at the time he and Bridget engaged in unprotected sex. Bridget thus has failed to identify the practical necessity for discovery of John’s sexual conduct subsequent to their honeymoon.
The Court of Appeal also erred in upholding discovery into John’s sexual behavior dating back years before he even met Bridget. Under the record as it currently stands, Bridget has failed to identify the practical necessity for discovery of John’s sexual conduct any earlier than the six months that preceded his negative HIV test.
John’s declaration in support of his motion for summary judgment states that he was tested for HIV in connection with a life insurance application on August 17, 2000, and includes a copy of the lab report. The results were negative. Based on information from the Centers for Disease Control that the *1201window period between exposure to HIV and the production of sufficient antibodies to detect the presence of the virus in the blood can last up to six months,11 John reasons that he “was necessarily HIV negative six months prior to August 17, i.e., mid-February 2000, and at every prior time in his life.” He therefore contends that any discovery related to his sexual history must be limited to the six-month window period. Bridget responds that John’s negative HIV test in August 2000 is “a mere allegation which defendant has advanced as a part of his ‘she-infected-me’ defense and which plaintiff intends to prove to be patently false. Obviously, discovery cannot serve to debunk a lie if discovery is thwarted by having to assume the truth of the lie.”
The defect in Bridget’s response is that John’s negative HIV test is not a mere allegation. John has supported his allegation with an applicant profile from Intellisys reflecting the results of his HIV test. If the test is accurate, and if the latency period for development of HIV antibodies is no longer than six months, John could not have been infected any earlier than February 2000. Under those circumstances, as Bridget’s counsel conceded at oral argument, John’s sexual behavior during that earlier period would not be relevant to the issue of when he became infected. In other words, Bridget has not demonstrated, under the heightened standard applicable to constitutional rights of privacy, a practical necessity for discovery of John’s sexual conduct before he could have been infected with HIV.
On the other hand, as Bridget’s counsel explained at oral argument, it is possible that Bridget could offer evidence to cast doubt on the results of the August 2000 HIV test, such as by challenging the accuracy or reliability of an insurance application test or by offering expert testimony that the test was inconsistent with John’s development of full-blown AIDS the following year. If Bridget were to offer some basis to question the August 2000 test, or to adduce evidence that the time period from exposure to the virus to the development of antibodies in the blood can be longer than six months, then she may be entitled to discovery covering a broader time period. That option remains open to Bridget on remand. Because Bridget has not yet done so, however, we must balance John’s constitutional right to privacy against Bridget’s need for discovery based on the record as it currently stands. We must therefore limit her discovery requests concerning John’s sexual behavior to the period between February 17, 2000, the earliest date at which John could have been infected, through July 2000, when the couple last had sexual relations.
*1202Finally, we emphasize that we have not been asked and therefore express no views as to what measures the trial court should employ to maintain the confidentiality of the materials produced in discovery. The propriety of in camera review, orders to seal documents, protective orders, and other measures is an issue that remains for the trial court on remand. (See Schnabel v. Superior Court, supra, 5 Cal.4th at p. 714.)
C. Whether Discovery Must Be Limited Because of the Physician-Patient Privilege
John also asserts that the medical information sought by the subpoenas is protected by the physician-patient privilege but concedes, as he must, that “[t]here is no privilege under this article as to a communication relevant to an issue concerning the condition of the patient in a proceeding to recover damages on account of the conduct of the patient if good cause for disclosure of the communication is shown.” (Evid. Code, § 999.) John contends that discovery must nonetheless be denied because a good cause showing should require at a minimum “an expert declaration regarding the [plaintiff’s] infection status; the probable exposure period; and a description of the plaintiff’s sexual history that establishes the defendant as a probable transmitter.”
John cites no authority for his contention that a plaintiff must essentially eliminate other possible agents of infection before discovery may proceed. (Cf. M.M.D. v. B.L.G., supra, 467 N.W.2d at pp. 647-648 [evidence was sufficient to support liability despite inability of medical expert to determine whether plaintiff’s herpes outbreak was due to a recent infection or a dormant virus].) The statutory standard is good cause, and Bridget has amply established good cause for disclosure of John’s medical records concerning HIV and AIDS: she has recently been diagnosed as HIV positive; John, too, has been diagnosed as HIV positive, but his viral infection has already progressed to full-blown AIDS; during the two years preceding Bridget’s diagnosis, she was dating John, engaged to him, and married to him; and the couple engaged in unprotected sex during that period. Bridget thus has offered far more than “conjecture” or a “speculative presumption” to justify the requested discovery. (Mendez v. Superior Court (1988) 206 Cal.App.3d 557, 570-571 [253 Cal.Rptr. 731].) Moreover, John has not offered any evidence to suggest that an expert could pinpoint the time period for Bridget’s exposure to the virus. We therefore find that the superior court did not abuse its discretion in overruling John’s objection under the physician-patient privilege.12
*1203IV. Disposition
The judgment of the Court of Appeal is reversed insofar as it affirmed the order compelling responses to plaintiff’s special interrogatories and requests for admission to the extent they seek information about John’s sexual history outside the time period between February 17, 2000, and the end of July 2000, and the matter is remanded for further proceedings consistent with the views herein.
George, C. J., Chin, J., and Corrigan, J., concurred.
We note that the Proposed Final Draft of section 18, subdivision (a) of the Restatement Third of Torts, Liability for Physical Harm, imposes a duty to warn or to adopt further precautions if “the defendant knows or has reason to know” of the risk and “that those encountering the risk will be unaware of it.” Included in the examples of the “range of defendant conduct that can give rise” to this duty is “the defendant who is about to come into intimate contact with the plaintiff ... for failing to warn the plaintiff that the defendant suffers from a communicable disease.” (Rest.3d Torts, Liability for Physical Harm (Proposed Final Draft No. 1, Apr. 1, 2005) § 18, com. a, p. 247.)
United States Department of Health and Human Services, Centers for Disease Control and Prevention (CDC), HIV/AIDS Prevention in the United States, FAQ: How can I Tell if I’m infected with HIV?, at <http://www.cdc.gov/hiv/pubs/faq/faq5.htm> (as of July 3, 2006).
“Chlamydia is known as a ‘silent’ disease because about three quarters of infected women and about half of infected men have no symptoms.” (CDC, Sexually Transmitted Diseases, Chlamydia—CDC Fact Sheet, at <http://www.cdc.gov/std/Chlamydia/STDFactChlamydia.htm> [as of July 3, 2006].)
“Although many men with gonorrhea may have no symptoms at all, some men have some signs or symptoms that appear two to five days after infection; symptoms can take as long as 30 days to appear. ...[][] In women, the symptoms of gonorrhea are often mild, but most women who are infected have no symptoms. Even when a woman has symptoms, they can be so non-specific as to be mistaken for a bladder or vaginal infection.” (CDC, Sexually Transmitted Diseases, Gonorrhea—CDC Fact Sheet, at <http://www.cdc.gov/std/gonorrhea/ STDFact-gonorrhea.htm> [as of July 3, 2006].)
“Many people infected with syphilis do not have any symptoms for years.” “It has often been called ‘the great imitator’ because so many of the signs and symptoms are indistinguishable from those of other diseases.” (CDC, Sexually Transmitted Diseases, Syphilis—CDC Fact Sheet, at <http://www.cdc.gov/std/Syphilis/STDFact-Syphilis.htm> [as of July 3, 2006].)
“Most people infected with HSV-2 [herpes simplex virus type 2] are not aware of their infection. . . . [T]hey may have very mild signs that they do not even notice or that they mistake for insect bites or another skin condition.” (CDC, Sexually Transmitted Diseases, Genital Herpes—CDC Fact Sheet, at <http://www.cdc.gov/std/Herpes/STDFact-Herpes.htm> [as of July 3, 2006].)
“Most HPV infections have no signs or symptoms; therefore, most infected persons are unaware they are infected, yet they can transmit the virus to a sex partner.” (CDC, Sexually Transmitted Diseases, Genital HPV Infection—CDC Fact Sheet, at <http://www.cdc.gov/std/ HPV/STDFact-HPV.htm> [as of July 3, 2006].)
At oral argument, John abandoned our dissenting colleagues’ contention that actual knowledge is an essential predicate to liability. He claimed instead that actual knowledge of HTV infection, as verified by a medical diagnosis or test, or constructive knowledge based on a very limited category of symptoms of HIV (namely, Kaposi’s sarcoma) or a medical opinion was required before an individual could be liable for negligent transmission of HTV. He also urged the court to “lock in the duty” he described so as to avoid having to consider “constantly evolving medical and epidemiological information” concerning the disease.
Once again, John has failed to cite any legal authority for the limited duty he proposes. Nonetheless, his concession demonstrates the appropriateness of imposing liability on those who, under the totality of the circumstances, have reason to know they are infected. As stated earlier, it is premature to decide here which physical symptoms, considered in isolation or in combination with conduct reasonably likely to have resulted in the transmission of the virus, would support a finding of liability for negligent transmission of HIV. The question of duty depends on the facts of a particular case, including available medical and epidemiological information. This opinion does not purport to offer a primer on proving the tort of negligent transmission of HTV, but inquires only whether the discovery Bridget has requested is relevant to the tort or is reasonably calculated to lead to the discovery of admissible evidence. We therefore decline John’s invitation to “lock in the duty” he has described.
In particular, we find remarkable our dissenting colleagues’ proposed rule that even when substantial evidence indicates an HIV-positive individual has reason to know of his or her infection, this individual owes no duty of care as a matter of law to any sexual partner, and that such a duty could arise only when the individual acquires actual knowledge of the infection— although neither Justice Werdegar nor Justice Moreno ever defines how actual knowledge may be established, other than to reject the definition Justice Kennard proposes. Thus, under their proposed rule, an intravenous drug user who knowingly shares needles daily with a circle of HIV-positive individuals and has symptoms “associated with HIV” (dis. opn. of Moreno, J., post, at p. 1214, fn. 1) owes no duty of care as a matter of law when he or she insists on engaging in unprotected sex with or donates blood to uninfected individuals. Or, to put it another way, a defendant spouse who was in a relationship that “contemplated sexual exclusivity,” who “represented himself as disease free and repeatedly insisted that the parties forgo the use of condoms,” and who had reason to know he was infected with HIV has no duty even to warn the other spouse. (Dis. opn. of Werdegar, J., post, at pp. 1210-1211.) None of the statutes cited by our colleagues even arguably suggests the Legislature intended these results.
The dissenting opinions rely also on a false dichotomy between tort recovery for those individuals who have been negligently infected with HTV and legislative efforts to build awareness of HTV through education and voluntary testing. Education and tort liability can—and invariably do—work hand in hand in preventing harmful behavior. (Developments in the Law: Sexual Orientation and the Law (1989) 102 Harv. L.Rev. 1508, 1530, fn. 77 [“Education and tort suits against persons transmitting AIDS through sexual conduct are other viable alternatives for deterring AIDS transmission”].) We likewise disagree with Justice Moreno that the best way to protect “the populations most vulnerable to infection” with HIV is to reduce the incentive of all infected persons to guard against transmission of the virus. (Dis. opn. of Moreno, J., post, at p. 1222.)
CDC, HTV/AIDS Prevention in the United States, FAQ: Symptoms; Testing; Treatment: How long after a possible exposure should I wait to get tested for HIV?, supra, at <http://www.cdc.gov/hiv/pubs/faq/faq9.htm> (as of July 3, 2006).
We note also that John has already propounded discovery concerning Bridget’s sexual history designed to uncover other possible agents of her infection. Those requests are not before us, and we express no views as to their propriety.