Epidemiologic Notes and Reports Acquired Immunodeficiency Syndrome (AIDS) in Western Palm Beach County, Florida

From July 1982 through September 15, 1986, 79 persons meeting the surveillance case definition for acquired immunodeficiency syndrome (AIDS) were reported from western Palm Beach County, Florida. These patients were residents of the towns of Belle Glade (62 case-patients), Pahokee (seven case-patients), and South Bay (10 case-patients) at the time of onset of their illnesses. The number of cases is shown by year of diagnosis in Figure 1. Based upon 1980 census data, the calculated cumulative incidence for AIDS in these three towns is 295/100,000 population. In comparison, the overall cumulative incidence for AIDS in the United States is 10.8/100,000.

Selected characteristics of these 79 AIDS patients are listed in Table 1. Sixty-four patients were male; all but three of the patients were at least 13 years of age. The three pediatric patients were born to mothers infected with human lymphotropic virus type-III/lymphadenopathy-associated virus (HTLV-III/LAV), the virus that causes AIDS.* Of the 76 adult patients, 63 (82.8%) were members of population groups known to be at increased risk for HTLV-III/LAV infection or were born in Haiti, a country in which heterosexual contact plays a major role in transmission of HTLV-III/LAV (1,2). The remaining 13 (11 men, two women) adult patients had no reported risk factors for AIDS, but 10 of these 13 died before epidemiologic investigations could be completed.

Compared with other adult AIDS case-patients reported from Florida in the period, adult AIDS patients from western Palm Beach County were more likely to be reported as heterosexual intravenous (IV) drug abusers (31.6% vs. 13.1%, p 0.05), as sex partners of persons at increased risk of having AIDS (35.5% vs. 18.5%, p 0.01), or as persons with no reported risk factors for AIDS (17.1% vs. 4.8%, p 0.01).

Detailed information is available for the 62 case-patients from Belle Glade. Most of the AIDS patients lived in an area in the central part of town, comprising a population of 7,207 persons (1980 Decennial Census, Neighborhood Statistics Program). This area of Belle Glade is characterized by high rates of IV drug abuse and sexually transmitted diseases (3). Investigations in May 1985, May 1986, and August 1986 revealed that 19 adults with AIDS in Belle Glade could be directly linked to at least one other reported AIDS case by sexual contact, by sharing of needles during IV drug abuse, or both. These linked patients account for 32.2% of the 59 adult AIDS case-patients reported from Belle Glade between February 1982 and August 1986. Five of the 10 adult women reported as having AIDS during this time were prostitutes; four of the five were also IV drug abusers.

To evaluate the prevalence of and risk factors for HTLV-III/LAV infection in Belle Glade, a community-wide study was conducted from February through September 1986 by the Florida Department of Health and Rehabilitative Services (DHRS) and CDC. The town was divided into neighborhoods as determined by the 1980 decennial census. A proportionate-sampling scheme was used to interview and test persons living in and around the neighborhoods in which most of the AIDS patients resided. Preliminary results of this study indicate that 30 (3.1%) of 959 persons tested had detectable antibodies to HTLV-III/LAV by both enzyme immunoassay and Western-blot methods. One of the 30 persons had been diagnosed as having AIDS.

Sex-, age-, and race-specific seroprevalence rates have been calculated for the first 736 persons for whom data entry has been completed. Fourteen (3.7%) of 378 males and 12 (3.4%) of 358 females had antibodies to HTLV-III/LAV. None of 121 children ages 2-10 years had antibodies to HTLV-III/LAV. Other HTLV-III/LAV-antibody prevalence rates by age group were as follow: 14 (8.9%) of 157 persons ages 18-29; seven (4.4%) of 160 persons ages 30-39; two (1.8%) of 113 persons ages 40-49; three (3.2%) of 91 persons ages 50-59; and none of 94 persons over 60 years of age. Eighty-eight percent of seropositive adults were ages 18-49 years; 90% of adult AIDS case-patients reported in the United States are in that same age group. Twenty-six (4.2%) of 616 black-not-Hispanic persons tested had antibodies to HTLV-III/LAV, including 13 (8.7%) of 150 persons born in Haiti. None of 42 Hispanic persons and none of 60 white-not-Hispanic persons were seropositive. There was no clustering of persons infected with HTLV-III/LAV within households, except for four instances of infection involving two pairs of sexual partners. Further analyses are in progress to determine specific risk factors for infection.

Arthropods have been hypothesized as a mode of HTLV-III/LAV transmission in Belle Glade (4). As a measure of exposure to different mosquito vectors and antibody prevalence, samples obtained during the serosurvey were tested by the serum dilution-plaque reduction neutralization method in the Division of Vector-Borne Viral Diseases, CDC, for antibodies to five arboviruses (Tensaw, Maguari, Keystone, Saint Louis encephalitis, and dengue-2) prevalent in South Florida or the Caribbean (Table 2). There was no significant difference in prevalence of antibodies to these arboviruses between HTLV-III/LAV-infected and -noninfected persons. The lack of association between detection of antibodies to HTLV-III/LAV and antibodies to these arboviruses extends the findings of an earlier pilot study that included these and four other arboviruses (Pahayokee, Shark River, Gumbo Limbo, and Mahogany Hammock) indigenous to South Florida (5). Reported by M Roberts, RN, Glades General Hospital, R Young, MD, Glades Health Center, J Howell, MD, MPH, Palm Beach County Public Health Unit, M Wilder, MD, Acting State Epidemiologist, Florida Dept of Health and Rehabilitative Svcs; Division of Vector-Borne Viral Diseases, AIDS Program Office, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: The high rate of AIDS in western Palm Beach County has focused national attention on this area. The cumulative AIDS incidence in this area (295/100,000 population) is comparable to that of the City of San Francisco (316/100,000) and the borough of Manhattan (270/100,000)--areas with the highest incidence of AIDS in the United States. In western Palm Beach County, the high cumulative rate is largely the result of high rates of AIDS among IV drug abusers and their sexual partners.

Thirteen (17.1%) of 76 adult patients in western Palm Beach County with AIDS had no reported risk factors. Although this proportion is significantly higher than in other areas in Florida, 10 of the 13 case-patients died before they could be comprehensively interviewed to obtain additional epidemiologic information on risk factors. Nationally, 72.9% of AIDS case-patients who were initially reported as persons without known risk factors, and who were available for follow-up, have been reclassified (6). AIDS cases are not categorized as resulting from heterosexual transmission unless the index partner of the AIDS patient is known a) to be infected with HTLV-III/LAV, b) to have AIDS, or c) to belong to another risk group. Therefore, if no such information is available concerning the relevant sexual partners, a case is characterized as having no risk factors.

Thus far, findings of the community-based study demonstrate a high prevalence of HTLV-III/LAV infection among younger adults of both sexes (i.e., 18-29 years of age), while no children and no adults over age 60 have had evidence of infection with HTLV-III/LAV. Additionally, serologic findings for household members of HTLV-III/LAV-infected persons did not show any evidence of viral transmission through casual contact. Infection with HTLV-III/LAV was not associated with arbovirus infection, suggesting that HTLV-III/LAV-infected persons were not more likely than persons without HTLV-III/LAV infection to have been exposed to mosquitoes. Thus, the hypothesis that arthropods have transmitted HTLV-III/LAV in Belle Glade is not supported by AIDS surveillance data, age-specific rates of HTLV-III/LAV infection, and the arbovirus serologic studies.

The available epidemiologic evidence suggests that HTLV-III/LAV infection in Belle Glade results predominantly from sexual transmission and the use of contaminated needles for injecting drugs intravenously. The U.S. Public Health Service has published guidelines to prevent sexual and drug-abuse-related transmission of HTLV-III/LAV (7). In this setting of a high cumulative rate of AIDS and a high prevalence of HTLV-III/LAV infection, programs to promote risk-reduction practices must be expanded and adopted. Additionally, voluntary serologic testing combined with health education and counseling should continue to be available to enhance reduction of HTLV-III/LAV transmission.

The ongoing analyses of the community-wide DHRS/CDC study should further clarify specific risk factors for HTLV-III/LAV infection in Belle Glade and provide a basis for additional public health recommendations for the prevention of infection with this virus.

References

1. Pape JW, Liautaud B, Thomas F, et al. The acquired immunodeficiency syndrome in Haiti. Ann Int Med 1985;103:674-8.

2. Castro KG, Fischl MA, Landesman SH, et al. Risk factors for AIDS

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