one study in North Carolina in 1987, 2.6% of 426 migrant workers were HIV seropositive (53). Persons positive for syphilis had higher rates of HIV infection (5.6%) than those who did not (2.2%). Estimates of the prevalence of HIV infection in other migrant and seasonal farm workers are limited. The transience of this population makes it difficult for health care workers to assess the health status of these persons, who frequently do not have access to health care.
In the Americas outside of the United States, HIV-1 infection has been predominantly documented among homosexual/bisexual men who initially had sexual relations with individuals from the United States. Subsequently indigenous transmission has evolved, and there is increasing evidence for heterosexual transmission within many Latin American countries (54). One aspect of HIV transmission throughout the region has been the documented high rate of infection among female prostitutes who provide their services in different countries. In one study of 80 international prostitutes who traveled to 27 countries, 38 (49%) were HIV seropositive, which was considerably higher than that of the general population (1%), homosexual men (10%), or local prostitutes (2%) in Dominica, their country of origin (55). In view of the low prevalence of HIV in nontraveling Dominican prostitutes, these women were probably infected outside of the country. Nevertheless, many of them returned to their home, resulting in further spread within their home country.
HIV was introduced relatively late into Asian countries. The first few cases of HIV infection were not documented until 1985, and it was not until 1988–1990 that the transmission of HIV escalated to epidemic proportions (56). A 1985 serosurvey of 600 individuals in Thailand including prostitutes, i.v. drug users, and STD patients revealed a very low HIV-1 seroprevalence (<0.5%) (57, 58). However, by 1988 HIV-1 began to spread rapidly among i.v. drug users to a prevalence of 40%. Seroconversion rates were as high as 3–5% per month (59). This wave of the HIV epidemic in i.v. drug users appeared to be followed by one among female prostitutes. The National Sentinel Survey conducted 1 year after the spread of HIV among i.v. drug users showed that about 44% of lower-class prostitutes in Chiang Mai were infected with HIV-1 (56). Nationally, the HIV seroprevalence among prostitutes increased steadily from 3.7% in 1989 to 15% in 1991 (Figure 6) This was followed by successive waves of transmission into male clients of the prostitutes and from them into the wives and girlfriends of these men in the general population. Based on the current available data, it is estimated that there