Epidemiologic Notes and Reports Heterosexual Transmission of Human T-Lymphotropic Virus Type III/Lymphadenopathy- Associated Virus

Acquired immunodeficiency syndrome (AIDS) is caused by a virus that is known to be transmitted through sexual contact and parenteral exposure to blood or blood products and from mother to child during the perinatal period.

In the United States, sexual contact is believed to be the only risk factor for 8,374 (64%) of the 13,061 AIDS cases among adults reported to CDC as of September 16, 1985. These sexual-contact cases include 8,241 homosexual or bisexual men with no other known risk factors for infection and 133 heterosexual men and women.

The heterosexual-contact cases are among persons who denied belonging to known AIDS risk groups, but reported sexual contact with a risk-group member or an AIDS patient of the opposite sex. The proportion of AIDS patients placed in this category has not changed significantly over time (p

0.15). The 133 heterosexual-contact cases include 118 women and 15 men, the majority of whom said they had sexual contact with intravenous (IV) drug abusers.

No risk factors have been identified for HTLV-III/LAV infection in 829 of the total AIDS cases reported to CDC. Of these 829 patients, 344 were born in developing countries where AIDS is known to exist. The remaining 485 cases constitute a proportion of AIDS patients that has not changed significantly over time (p

0.15). Of these patients with no identified risk, 99 were available for in-depth interviews. Twenty-three (34%) of the 68 men gave histories of sexual contact with female prostitutes. One (3%) of the 31 women gave a history of prostitution.

Serologic evidence of HTLV-III/LAV infection in female prostitutes has been shown in preliminary studies from several American cities. Of 92 prostitutes tested in Seattle, five (5%) had HTLV-III antibody detected by the enzyme immunoassay (EIA) tests of two manufacturers. In Miami, Florida, 10 (40%) of 25 prostitutes attending an AIDS screening clinic had HTLV-III antibody detected by both EIA and Western blot methods. Eight of the 10 seropositive women reported previous IV drug abuse. Reported by H Handsfield, MD, Seattle-King County Dept of Public Health, J Kobayashi, MD, State Epidemiologist, Washington State Dept of Social and Health Svcs; M Fischl, MD, G Dickinson, MD, University of Miami School of Medicine, J Witte, MD, Florida Dept of Health and Rehabilitative Svcs; AIDS Br, Div of Viral Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Transmission of HTLV-III/LAV from heterosexual men to their female sexual partners has been well established in studies from the United States and elsewhere. Several published reports from the United States describe the occurrence of AIDS in heterosexual couples, where only the male partner had a known AIDS risk factor (1-3). A study in Rwanda and Belgium described AIDS or related conditions in 42 African women, including 10 prostitutes, who denied IV drug abuse (4).

Studies of AIDS patients from several developing countries also indicate that female-to-male sexual transmission of HTLV-III/LAV infection occurs in those settings and emphasize the role of female prostitutes in this transmission. In Zaire, the ratio of male-to-female AIDS cases is 1.1:1 (5). A case-control study of heterosexual African men with AIDS or related conditions in Rwanda and Belgium showed a significant association of HTLV-III/LAV infection with a history of contact with prostitutes and with an increased number of female partners per year (4). A case-control study of Haitian men with AIDS in Miami and New York City showed a significant association of AIDS with a history of prostitute contact and with a history of sexually transmitted diseases, suggesting that sexual contact may be a major method of transmission in these heterosexual men (6).

For persons born in the United States, female-to-male sexual transmission of HTLV-III/LAV has been less evident than male-to-female sexual transmission. The reasons for reported differences in the epidemiologic pattern of HTLV-III/LAV infections in the United States and certain developing countries are not clear. However, there are at least two possible explanations for the paucity of reported male "heterosexual contact" AIDS patients in the United States. First, female-to-male transmission of HTLV-III/LAV may be less efficient than male-to-female transmission, as has been reported for gonococcal infections (7,8). Second, the proportion of women among infected persons is relatively small. Of the 2,665 reported heterosexual AIDS patients with known risk factors in the United States, only 647 (24%) are women. The inclusion of 1,427 AIDS cases among bisexual men would further decrease the proportion of women among potential transmitters of infection. If the distribution of HTLV-III/LAV infected persons in the population is similar to the distribution of AIDS patients, infected heterosexual men would outnumber infected women by a ratio of 5:1.

While additional evidence for female-to-male transmission of HTLV-III/LAV in the United States is being sought, it would seem prudent to assume that such transmission occurs. In all other sexually transmitted infections, transmission is bidirectional, and HTLV/III/LAV appears to be spread bidirectionally in other populations. HTLV-III/LAV has been isolated from semen (9,10) and, presumably, would be present in the menstrual blood and the lymphocytes found in cervical and vaginal secretions of infected women. Attempts to isolate the virus from cervical and vaginal secretions are in progress.

All sexually active persons should realize that their risks of acquiring infection are greatly increased by having sexual intercourse with members of known AIDS risk groups or with persons who are the sexual contacts of risk-group members. Sexually active persons should also recognize that, as with other sexually transmitted diseases, the greater the number of sexual partners, the greater the risk of possible HTLV-III/LAV infection. Consistent use of condoms should assist in preventing infection with HTLV-III/LAV, but their efficacy in reducing transmission has not yet been proven.

References

1. Harris C, Small CB, Klein RS, et al. Immunodeficiency in female sexual partners of men with the acquired immunodeficiency syndrome. N Engl J Med 1983;308:1181-4.

2. Pitchenik AE, Shafron RD, Glasser RM, Spira TJ. The acquired immunodeficiency syndrome in the wife of a hemophiliac. Ann Intern Med 1984;100:62-5.

3. Kreiss JK, Kitchen LW, Prince HE, Kasper CK, Essex M. Antibody to human T-lymphotropic virus type III in wives of hemophiliacs. Evidence for heterosexual transmission. Ann Intern Med 1985;102:623-6.

4. Clumeck N, Van de Perre P, Carael M, Rouvroy D, Nzaramba D. Heterosexual promiscuity among African patients with AIDS. (Letter) N Engl J Med 1985;313:182.

5. Piot P, Quinn TC, Taelman H, et al. Acquired immunodeficiency syndrome in a heterosexual population in Zaire. Lancet 1984;ii:65-9.

6. Castro KG, Fischl MA, Landesman SH, et al. Risk factors for AIDS among Haitians in the United States. Atlanta, Georgia: International Conference on AIDS, April 16, 1985.

7. Hooper RR, Reynolds GH, Jones OG, et al. Cohort study of venereal disease. I: the risk of gonorrhea transmission from infected women to men. Am J Epidemiol 1978;108:136-44.

8. Platt R, Rice PA, McCormack WM. Risk of acquiring gonorrhea and prevalence of abnormal adnexal findings among women recently exposed to gonorrhea. JAMA 1983;250:3205-9.

9. Zagury D, Bernard J, Leibowitch J, et al. HTLV-III in cells cultured from semen of two patients with AIDS. Science 1984;226:449-51.

10. Ho DD, Schooley RT, Rota TR, et al. HTLV-III in the semen and blood of a healthy homosexual man. Science 1984;226:451-3.

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