June 7, 2000
Serologic tests for antibodies to HIV, developed in 1984 (Sarngadharan et al., 1984; Popovic et al., 1984; reviewed in Brookmeyer and Gail, 1994), have enabled researchers to conduct hundreds of seroprevalence surveys throughout the world. Using these tests, investigators have repeatedly demonstrated that the occurrence of AIDS-like illnesses in different populations has closely followed the appearance of HIV antibodies (U.S. Bureau of the Census, 1994). For example, retrospective examination of sera collected in the late 1970s in association with hepatitis B studies in New York, San Francisco and Los Angeles suggests that HIV entered the U.S. population sometime in the late 1970s (Jaffe et al., 1985a). In 1978, 4.5 percent of men in the San Francisco cohort had antibodies to HIV (Jaffe et al., 1985a). The first cases of AIDS in homosexual men in San Francisco were reported in 1981, and by 1984, more than two-thirds of the San Francisco cohort had HIV antibodies and almost one-third had developed AIDS-related conditions (Jaffe et al., 1985a). By the end of 1992, approximately 70 percent of 539 men in the San Francisco cohort with a well-documented date of HIV seroconversion before 1983 had developed an AIDS-defining condition or had a CD4+ T cell count of less than 200/mm3; another 11 percent had CD4+ T cell counts between 200 and 500/mm3 (Buchbinder et al., 1994) (Figure 3).
Retrospective tests of the U.S. blood supply have shown that, in 1978, at least one batch of Factor VIII was contaminated with HIV (Evatt et al., 1985; Aronson, 1993). Factor VIII was given to some 2,300 males in the United States that year. In July 1982, the first cases of AIDS in hemophiliacs were reported (CDC, 1982c). Through Dec. 31, 1994, 3,863 individuals in the United States with hemophilia or other coagulation disorders had been diagnosed with AIDS (CDC, 1995a).
Elsewhere in the world, a similar chronological association between HIV and AIDS has been noted. The appearance of HIV in the blood supply has preceded or coincided with the occurrence of AIDS cases in every country and region where cases of AIDS have been reported (Institute of Medicine, 1986; Chin and Mann, 1988; Curran et al., 1988; Piot et al., 1988; Mann, 1992; Mann et al., 1992; U.S. Bureau of the Census, 1994). For example, a review of serosurveys associated with dengue fever in the Caribbean found that the earliest evidence of HIV infection in Haiti appeared in samples from 1979 (Pape et al., 1983, 1993); the first cases of AIDS in Haiti and in Haitians in the United States were reported in the early 1980s (CDC, 1982e; Pape et al., 1983, 1993).
In Africa between 1981 and 1983, clinical epidemics of chronic, life-threatening enteropathic diseases ("slim disease"), cryptococcal meningitis, progressive KS and esophageal candidiasis were recognized in Rwanda, Tanzania, Uganda, Zaire and Zambia, and in 1983 the first AIDS cases among Africans were reported (Quinn et al., 1986; Essex, 1994). The earliest blood sample from Africa from which HIV has been recovered is from a possible AIDS patient in Zaire, tested in connection with a 1976 Ebola virus outbreak (Getchell et al., 1987; Myers et al., 1992).
Serologic data have suggested the presence of HIV infection as early as 1959 in Zaire (Nahmias et al., 1986). Other investigators have found evidence of HIV proviral DNA in tissues of a sailor who died in Manchester, England, in 1959 (Corbitt et al., 1990). In the latter case, this finding may have represented a contamination with a virus isolated at a much later date (Zhu and Ho, 1995).
HIV did not become epidemic until 20 to 30 years later, perhaps because of the migration of poor and young sexually active individuals from rural areas to urban centers in developing countries, with subsequent return migration and, internationally, due to civil wars, tourism, business travel and the drug trade (Quinn, 1994).