This report updates data for acquired immunodeficiency syndrome (AIDS) and human immunodeficiency virus (HIV) infection associated with heterosexual transmission and is based on national AIDS surveillance, HIV seroprevalence surveys, and studies of populations at varying levels of risk for heterosexual transmission. HETEROSEXUALLY ACQUIRED AIDS CASES

By March 31, 1989, 89,501 AIDS cases in persons greater than or equal to 13 years of age had been reported to CDC; 3962 (4%) of these were attributed to heterosexual transmission. Forty-one percent of heterosexual transmission cases were reported in the preceding 12 months, compared with 36% of all other AIDS cases. Of the heterosexualtransmission cases, 1337 (34%) persons were born in countries where heterosexual transmission is a major route of HIV infection; 2625 (66%) persons reported heterosexual contact with a partner with or at increased risk for HIV infection (Table 1, page 429). These heterosexual contacts included intravenous-drug users (IVDUs) (72%), bisexual men (10%), recipients of blood or clotting factor concentrates (3%), persons born in countries where heterosexual contact is the major route of transmission (2%), and persons with HIV infection or AIDS and an unreported risk (13%). Men were proportionately more likely than women to report partners from countries where heterosexual contact is the major route of transmission (5%, compared with 1%) or partners with an unreported risk (19%, compared with 11%).

While the number of heterosexually acquired AIDS cases reported each year has increased, the overall proportion has remained relatively stable--from 5.2% of adult AIDS cases reported in 1983 to 4.9% in 1988. However, the composition of the group has changed over time; since 1986, persons reporting sexual contact with a partner at risk have outnumbered HIV-infected persons born in countries with predominantly heterosexual HIV transmission (Figure 1). From 1987 to 1988, the percentage increase for heterosexually transmitted AIDS among persons born in countries where heterosexual contact is the major route of transmission was 41%, compared with a 97% increase for persons with an "at-risk" partner.

Of the 2625 persons with an "at-risk" partner, 672 (26%) were men and 1953 (74%) were women, representing 0.8% and 25% of AIDS cases in all males and females, respectively. Men were older than women (mean age: 40, compared with 34 years, respectively). Forty-seven percent were black, 29% white, 23% Hispanic, 0.6% Asian Pacific Islander, and 0.2% American Indian/Alaskan Native. In the 12 months before March 31, 1989, blacks and Hispanics had the highest incidences of heterosexually acquired AIDS per 100,000 population: 3.1 and 3.5, respectively, for women and 1.9 and 0.8, respectively, for men, compared with 0.3 and 0.2 cases per 100,000 for white women and men, respectively. Overall, rates for blacks and Hispanics were 12 and 10 times, respectively, the rate for whites.

Forty-six states, the District of Columbia, Puerto Rico, and the Virgin Islands have reported AIDS cases in persons who had heterosexual contact with an "at-risk" partner. The geographic distributions of women who were sex partners of bisexual men or men who used IV drugs were similar to those of men with AIDS from these two groups (Table 2A and 2B). In contrast, the geographic distribution of men who reported heterosexual contact with a woman who used IV drugs was different from that of women with AIDS who were IVDUs (Table 2C). For example, New York accounted for 40% of female IVDUs with AIDS but for only 4% of men who reported sexual contact with a female IVDU, and Florida accounted for 25% of men reporting IV-drug-using partners but for only 9% of female IVDUs with AIDS. HETEROSEXUAL TRANSMISSION OF HIV IN SURVEYED POPULATIONS

Risk for HIV transmission from infected persons to their steady heterosexual partners without other risks varied in 26 studies that included at least 20 couples each; in heterosexual partners, HIV seroprevalence ranged from 0 to 58% (median: 24%) (1,2).

Female prostitutes are at increased risk for acquisition and potential transmission of HIV infection. In the United States, HIV infection in prostitutes is strongly associated with IV-drug use. In a multicity study, HIV antibody was detected in 180 (13%) of 1378 female prostitutes; 80% of the infected prostitutes reported using IV drugs (3). In prostitutes with no histories or findings suggestive of IV-drug use, HIV seroprevalence was 5%; HIV seropositivity in this group was greater among blacks and Hispanics and among those with greater than 200 lifetime nonpaying sex partners.

Seroprevalence data are limited for heterosexuals who are not sex partners of persons known to be infected or at increased risk. Data on heterosexuals from sexually transmitted disease (STD) clinics indicate that HIV seroprevalence is highest among IVDUs and their sex partners. In an ongoing study begun in January 1988 of New York City STD clinic clients who consented to be interviewed and tested for HIV, 63 (47%) of 134 IVDUs and 25 (13%) of 193 persons with a sex partner who used IV drugs were HIV-positive (4). In addition, a 1987 survey of STD clinic attendees in Baltimore detected HIV antibody in 34 (15%) of 224 men and 14 (22%) of 65 women with self-reported histories of IV-drug use and 18 (11%) of 170 women who reported sexual contact with men who were bisexual or used IV drugs (5). Among clinic patients who did not report any risks for HIV infection, including male homosexual contact, IV-drug use, or sexual contact with a partner at increased risk, HIV seroprevalence was 4% (20/571) in men and 5% (9/196) in women in New York City (4), 3% (56/2068) in men and 2% (20/1115) in women in Baltimore (5), and 0.2% (4/1634) in men and 0 (0/940) in women in Denver (6).

HIV transmission among heterosexually active persons without known risks in either partner also can be monitored by interviewing seropositive civilian recruit applicants for military service and blood donors. HIV seropositivity lower than that in comparable segments of the general population would be expected because both groups are screened to exclude persons with histories of male homosexual contact, IV-drug use, or hemophilia. Seropositive recruit applicants and blood donors therefore might be expected to include a relatively large proportion of persons with HIV infection acquired from heterosexual partners who were not suspected or known to be infected.

Among approximately 1.5 million male and 253,547 female civilian recruit applicants screened during October 1985-September 1988, 0.15% and 0.07%, respectively, were HIV seropositive (2). In limited follow-up studies of seropositive male recruit applicants, most had risk factors for HIV infection other than heterosexual contact. In New York City and Denver, 19 (86%) of 22 and 10 (91%) of 11 seropositive male applicants, respectively, admitted male homosexual contact or IV-drug use; the remaining four men reported contact with a female prostitute (7,8). Too few seropositive women were available for analysis.

Among 1.3 million male and 1.2 million female first-time blood donors tested during April 1985-September 1988, 0.067% and 0.014%, respectively, were HIV-seropositive (2). In an ongoing follow-up study of seropositive blood donors in 16 cities, 50% of interviewed donors reported male homosexual contact or IV-drug use; 18 (8%) of 228 interviewed seropositive males and 43 (57%) of 76 women reported heterosexual contact with a partner at risk for HIV infection; women were more likely than men (36% and 29%, respectively) to have no risk identified (9). Reported by: Local, state, and territorial health departments. AIDS Program, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: In general, a person's risk of acquiring HIV infection through sexual contact depends on 1) the number of different partners, 2) the likelihood (prevalence) of HIV infection in these partners, and 3) the probability of virus transmission during sexual contact with an infected partner (10). Virus transmission, in turn, may be affected by biologic factors, such as concurrent STD infections in either partner (e.g., genital ulcer disease); behavioral factors, such as type of sex practice and use of condoms; or varying levels of infectivity in the source partner related to clinical stage of disease (11). Based on these factors, the risk for HIV infection is highest for a regular partner of an HIV-infected person. Persons who have sex partners with risk factors for HIV infection or who themselves have multiple partners from urban settings with high rates of IV-drug and "crack" cocaine use (4,12), prostitution, and other STDs are also at increased risk.

Surveillance data for heterosexual transmission of HIV infection need to be interpreted cautiously. The actual number of AIDS cases reported to be associated with heterosexual transmission probably underestimates the role of this mode of spread. Nearly 3000 persons classified as bisexual men and IVDUs and persons with hemophilia also reported heterosexual contact with a person at risk. Therefore, some of these persons may have acquired HIV through heterosexual contact rather than through these other routes. Similarly, some persons with an undetermined risk may have become infected through heterosexual contact. Persons with an undetermined risk are demographically similar to AIDS patients who report IV-drug use or sexual contact with a partner at risk. Nearly 40% of persons with an undetermined risk have self-reported histories of an STD, and one third of men reported sexual contact with a female prostitute (13). Conversely, some persons with AIDS attributed to heterosexual transmission may have other unacknowledged or undetermined risk factors. For example, inconsistencies in the geographic distribution of men who reported sexual contact with a female IVDU, as well as the tendency of men to have partners with an unknown risk, suggests that some of these men may be misclassified. Underascertainment of heterosexual transmission among men probably exists in other areas.

Compared with AIDS case data, seroprevalence surveys reflect more recent patterns of HIV infection. However, only limited information regarding the spread of heterosexually acquired HIV infection is available from current surveys because relatively few collect information about risk factors. Additional follow-up studies of STD clinic patients, seropositive blood donors, and civilian recruit applicants are now under way or being implemented to aid in monitoring the level and trends of heterosexual transmission (14).

Both AIDS surveillance and HIV seroprevalence follow-up studies indicate that an appreciable proportion of HIV infection among women in the United States is acquired through heterosexual contact. Because HIV seroprevalence is greater in men, a woman is more likely than a man to have an infected heterosexual partner. Women may also be unaware of the infection status of their male partners, as suggested by data on civilian recruit applicants. HIV seroprevalence rates among male recruit applicants have declined since 1985; in contrast, rates among female applicants have remained stable, suggesting that women may be less likely to self-defer because they do not know or suspect they are infected (2). The predominance of heterosexually acquired HIV infections in women of reproductive age has important implications for perinatal HIV transmission; nearly 30% of children with AIDS were infected by their mothers who acquired infection through heterosexual contact.

Recent increases in syphilis among heterosexuals, particularly among prostitutes, drug users, and their sexual contacts (15,16), indicate the need for more intensive application of recommended measures (17,18) to interrupt sexual and drug-use- related transmission of HIV infection. These measures include: --development of community health education programs aimed at populations at increased risk; !participation in mutually monogamous relationships or reduction of the number of sex partners; --use of condoms to prevent exposure to semen and infected lymphocytes; --enrollment of drug users in programs to eliminate use of IV-drugs; and --increased voluntary HIV testing and counseling of persons at increased risk in settings such as STD and family planning clinics and drug-treatment programs.

References

1. CDC. Human immunodeficiency virus infection in the United States: a

review of current knowledge. MMWR 1987;36(suppl S-6). 2. CDC. AIDS and human immunodeficiency virus infection in the United States: 1988 update. MMWR 1989:38(suppl S-4).

3. Darrow WW, Bigler W, Deppe D, et al. HIV antibody in 640 U.S. prostitutes with no evidence of intravenous (IV)-drug abuse (Abstract). IV International Conference on AIDS. Book 1. Stockholm, June 12-16, 1988:273.

4. Chiasson MA, Stoneburner RL, Telzak E, Hildebrandt D, Schultz S, Jaffe HW. Risk factors for HIV-1 infection in STD clinic patients: evidence for crack-related heterosexual transmission (Abstract). V International Conference on AIDS. Montreal, June 4-9, 1989:117.

5. Quinn TC, Glasser D, Cannon RO, et al. Human immunodeficiency virus infection among patients attending clinics for sexually transmitted diseases. N Engl J Med 1988;318:197-203.

6. Judson F, Cohn D, Douglas J. HIV seroprevalence in heterosexual men and women, Denver Metro STD Clinic, 1985-1988 (Abstract). V International Conference on AIDS. Montreal, June 4-9, 1989:87.

7. Stoneburner RL, Chiasson MA, Solomon K, Rosenthal S. Risk factors in military recruits positive for HIV antibody (Letter). N Engl J Med 1986;315:1355.

8. Dillon BA, Spencer N. Follow-up counseling and risk behavior assessment of HIV antibody positive military recruits (Abstract). III International Conference on AIDS. Washington, DC, June 1-5, 1987:42.

9. Peterson L and the HIV Blood Donor Study Group. Surveillance for unusual modes of HIV transmission in the USA--a 5-year multicenter study of blood donors (Abstract). V International Conference on AIDS. Montreal, June 4-9, 1989:83. 10. Peterman TA, Curran JW. Sexual transmission of human immunodeficiency virus. JAMA 1986;256:2222-6. 11. Holmes KK, Kreiss J. Heterosexual transmission of human immunodeficiency virus: overview of a neglected aspect of the AIDS epidemic. J Acquired Immune Deficiency Syndromes 1988;1:602-10. 12. Chaisson RE, Bacchetti P, Osmond D, Brodie B, Sande MA, Moss AR. Cocaine use and HIV infection in intravenous drug users in San Francisco. JAMA 1989;261:561-5. 13. Castro KG, Lifson AR, White CR, et al. Investigations of AIDS patients with no previously identified risk factors. JAMA 1988;259:1338-42. 14. Dondero TJ, Jr, Pappaioanou M, Curran JW. Monitoring the levels and trends of HIV infection: the Public Health Service's HIV surveillance program. Public Health Rep 1988;103:213-20. 15. CDC. Continuing increase in infectious syphilis--United States. MMWR 1988;37:35-8. 16. CDC. Relationship of syphilis to drug use and prostitution--Connecticut and Philadelphia, Pennsylvania. MMWR 1988;37:755-8,764. 17. CDC. Additional recommendations to reduce sexual and drug abuse-related transmission of human T-lymphotropic virus type III/lymphadenopathy-associated virus. MMWR 1986;35:152-5. 18. CDC. Public Health Service guidelines for counseling and antibody testing to prevent HIV infection and AIDS. MMWR 1987;36:509-15,521-2.

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