Current Trends Human T-Lynphotropic Virus Type III/ Lymphadenopathy-Associated Virus Antibody Prevalence in U.S. Military Recruit Applicants

From October 1, 1985, through March 31, 1986, as part of medical evaluation of individuals volunteering for military service, the U.S. Department of Defense tested 308,076 recruit applicants for serologic evidence of infection with human T-lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV), the etiologic retrovirus of acquired immunodeficiency syndrome (AIDS).* Blood samples were obtained at 71 Military Entrance Processing Stations. The screened population consisted predominately of young adults in their late teens (54%) and early twenties (33% were 20-25 years old). Eighty-five percent were male, and 77% were white. Sera were tested by a single contracting laboratory using a commercial human T-lymphotropic virus type III (HTLV-III) enzyme-linked immunosorbent assay (ELISA) test (Electronucleonics, Inc.). All samples repeatably reactive by ELISA were also subjected to confirmation testing by the Western blot. Blots were considered positive if antibodies to gp 41 and/or p24+p55 were detected. Recruit applicants with confirmed HTLV-III/LAV antibody are excluded from military service.

The mean prevalence of confirmed positive tests was 1.5 per 1,000 recruit applicants. Antibody prevalence increased progressively with age (Table 1), a pattern consistent throughout the country (Table 2). The seroprevalence was higher among the 265,361 men of all ages, 1.6/1,000, than among the 42,715 women, 0.6/1,000. The ratio of male-to-female prevalence rates was 3:1. Prevalence also varied by race: for the 237,586 whites, the rate was 0.9/1,000; for the 55,185 blacks, 3.9/1,000; and for the 15,305 applicants of other racial groups, 2.6/1,000. The relationships of seroprevalence rates by sex and race remain when the data are adjusted by age.

Seroprevalence rates (Table 2) were highest in the coastal regions of the country other than New England. Rates were lowest in New England and in the inland regions. Based on preliminary analysis by county, the highest HTLV-III antibody rates were found in recruit applicants from major urban centers and lowest in those from rural areas. Reported by the Health Studies Task Force, Office of the Assistant Secretary of Defense (Health Affairs); Dept of Virus Disease, Div of Preventive Medicine, Walter Reed Army Institute of Research; Surveillance and Evaluation Br, AIDS Program, Center for Infectious Disease, CDC.

Editorial Note

Editorial Note: Although there is considerable knowledge regarding the distribution of reported cases of AIDS in the United States (1), there has been much less information about the prevalence of infection with HTLV-III/LAV. Studies of HTLV-III/LAV antibody prevalence have primarily involved selected high-risk groups, including homosexual men (24%-68% positive) (2-5), intravenous (IV) drug abusers (2%-72% positive) (6-8), and hemophilia patients (40%-88% positive) (9-11). The limited published data from blood-bank screening programs, where persons in high-risk groups are specifically discouraged from donating, indicate a confirmed antibody prevalence nationally of less than 0.4/1,000 (12).

The Department of Defense medical evaluation program provides additional information on the geographic and demographic factors associated with HTLV-III/LAV infection in the United States. The population of individuals volunteering for military service may not be representative of the U.S. population at large due to the spontaneous, if partial, self-exclusion of hemophilia patients, actively homosexual men, and current IV drug abusers. However, the data suggest the following: (1) While the highest seroprevalence occurs among those over 25 years old, the age of acquisition of confirmed antibody (and by implication, infection) can often be in the late teens and early twenties. Age at diagnosis of reported AIDS is older, with a median of 32-35 years, depending on risk group, race, and sex. Only 0.7% of reported cases among adults/adolescents occur between 13 and 20 years of age; 6.5% develop between 21 and 25 years; the remaining 92.8% are diagnosed at or after 26 years of age. (2) The ratio of seroprevalence between male and female recruit applicants is 3:1. This is much lower than the ratio of 13:1 observed among all AIDS cases, but like the 3:1 ratio among other AIDS patients if homosexual and hemophilia-associated cases are excluded. (3) The ratio of seroprevalence rates of black to white recruit applicants (4:1) is intermediate between the 2.6 relative risk for blacks among all AIDS patients (25.2% of cases are among non-Hispanic blacks, who comprise 11.5% of the population (13)) and the 8.3 relative risk for blacks among AIDS patients not associated with either homosexuality or hemophilia (blacks comprise 52.0% of these cases). The data do not yet permit a detailed analysis of seroprevalence differences by Hispanic ethnicity. (4) The geographic distribution of seroprevalence among recruits is generally consistent with the incidence of cases, both by region and by urban versus rural residence. More detailed geographic analysis will be possible when cumulative data are available from screening additional recruits.

As in the case with serologically positive blood donors (14), recruit applicants with confirmed positive antibody are informed of their status and its implication regarding infection with HTLV-III/LAV; they are counseled on reducing the risk of transmission to others through sexual contact, sharing IV needles, or other exchanges of blood or body fluids.

Counselling and testing for HTLV-III/LAV antibody should be offered to persons who may have already been infected as a result of intimate contact with the seropositive recruit applicant (i.e., sexual partners, persons with whom needles have been shared, infants born to seropositive mothers). In addition, seropositive individuals should be interviewed by an experienced investigator to determine their risk factors for infection. This, coupled with observation on suitable controls, would facilitate determining modes of acquisition and evaluating current trends in risk of exposure to the virus in these populations.

The continued analysis of data emerging from the HTLV-III/LAV serologic screening of military recruit applicants will permit the examination of the extent and the trends over time of infection with the causative agent of AIDS in this sentinel population.

References

1. Peterman TA, Drotman DP, Curran JW. Epidemiology of the acquired immunodeficiency syndrome (AIDS). Epidemiol Rev 1985;7:1-21.

2. Phair J. Prevalence and correlates of HTLV-III antibodies among 5000 gay men in 4 cities. Multicenter AIDS Cohort Study (MACS) (Abstract). 25th Interscience Conference on Antimicrobial Agents and Chemotherapy. Minneapolis: America Society for Microbiology, 1985:229.

3. Collier AC, Barnes RC, Handsfield HH. Prevalence of antibody to LAV/HTLV-III among homosexual men in Seattle. Am J Public Health 1986;76:564-5.

4. Schwartz K, Visscher BR, Detels R, Taylor J, Nishanian P, Fahey JL. Immunological changes in lymphadenopathy virus positive and negative symptomless male homosexuals: two years of observation (Letter). Lancet 1985;II:831-2.

5. Darrow WW, Jaffe HW, O'Malley PM, et al. Sexual practices and HTLV-III/LAV infections in a cohort of homosexual male clinic patients, San Francisco (Abstract). 6th International Meeting of the International Society for STD Research. Brighton: International Society for STD Research, 1985:31.

6. Levy N, Carlson JR, Hinrichs S, Lerche N, Schenker M, Gardner MB. The prevalence of HTLV-III/LAV antibodies among intravenous drug users attending treatment programs in California: a preliminary report (Letter). N Engl J Med 1986;314:446.

7. Weiss SH, Ginzburg HM, Goedert JJ, et al. Risk for HTLV-III exposure and AIDS among parenteral drug abusers in New Jersey (Abstract). Atlanta: International Conference on Acquired Immunodeficiency Syndrome (AIDS), 1985:44.

8. Spira TJ, DesJarlais DC, Bokos D, et al. HTLV-III/LAV antibodies in intravenous drug (IV) abusers--comparison of high and low risk areas for AIDS (Abstract). Atlanta: International Conference on Acquired Immunodeficiency Syndrome (AIDS), 1985:84.

9. Ragni MV, Tegtmeier GE, Handwerk-Leber C, Lewis, JH, Mayer WL, Spero JA. Prevalence and seroconversion of human T-lymphotropic retrovirus (HTLV-III) antibody in patients with hemophilia (Abstract). Atlanta: International Conference on Acquired Immunodeficiency Syndrome (AIDS), 1985:74.

10. Jason J. McDougal JS, Holman RC, et al. Human T-lymphotropic retrovirus type III/lymphadenopathy-associated virus antibody. Association with hemophiliacs' immune status and blood component usage. JAMA 1985;253:3409-15.

11. Goedert JJ, Sarngadharan MG, Eyster ME, et al. Antibodies reactive with human T cell leukemia viruses in the serum of hemophiliacs receiving factor VIII concentrate. Blood 1985;65:492-5.

12. Schorr JB, Berkowitz A, Cumming PD, Katz AJ, Sandler SG. Prevalence of HTLV-III antibody in American blood donors (Letter). N Engl J Med 1985;313:384-5.

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