Epidemic of AIDS Defies Pattern in South Florida City

In early February, medical detectives will begin knocking on doors in a ghetto area of this sugar-cane-farming town of 20,000 in hopes of solving one of the major puzzles of the AIDS epidemic: Why this south Florida community has more AIDS cases per capita than any other city in the United States.

Unlike the prevailing figures in the rest of the nation, nearly half of Belle Glade’s 41 cases reported to date are neither gay men, intravenous drug users nor hemophiliacs--who, elsewhere around the country, make up more than 90% of all AIDS cases.

The focus of the federal and state researchers will be a squalid 10-square-block ghetto that Palm Beach County’s housing director has called “unfit for human habitation.”

Two North Miami physicians are convinced that the ghetto’s dismal environment is playing a major role in Belle Glade’s AIDS outbreak.

Mosquitoes or Prostitutes

Drs. Caroline MacLeod and Mark Whiteside point specifically to the overcrowded, unsanitary living conditions, the rat infestation and, above all, the mosquitoes that breed with abandon in any container that holds water.

Researchers from the federal Centers for Disease Control and the Florida health department doubt that mosquitoes--like contaminated needles shared by drug users--have a role in AIDS transmission. Instead, they suspect a stronger role for heterosexual transmission than previously known, possibly involving prostitutes.

If either theory is buttressed by the study’s findings, then the dimensions of the AIDS epidemic will have significantly expanded, since mosquitoes have not been implicated thus far in the transmission of AIDS and heterosexuals have played only a relatively minor role.

The study could also shed further light on why 25% of all AIDS patients in the United States are black, although blacks make up only 10% of the general population. One assumption has been that a disproportionate number of blacks are intravenous drug users; another theory has been that blacks may be genetically predisposed to the disease.

The study, in addition, may clarify why a disproportionately large number of Haitians, who were once considered to be a high-risk group, have contracted AIDS.

At least 4,000 of Belle Glade’s 20,000 residents are migrant workers, most of whom are Haitians or American-born blacks.

Some of the migrant workers live in company housing outside the ghetto. But many--including nearly all the AIDS patients--live in the most ramshackle part of the town.

Pilot Studies Last Summer

MacLeod and Whiteside were the first to report the unusual AIDS cluster in Belle Glade, and their report in April triggered two small pilot studies last summer that recommended that a larger study be done.

The upcoming study involves more than 1,000 ghetto residents. It seeks to determine, through blood tests, the prevalence of HTLV-III, the virus that causes AIDS, in the community as well as the subjects’ exposure to 10 different mosquito-borne viruses. The researchers will also conduct interviews to gather information on sexual habits and personal and family history.

The study will take four months in the field and another four months to analyze the data, according to Dr. Ken Castro, the Centers for Disease Control epidemiologist who is coordinating it.

“Certainly something is going on in Belle Glade . . . but I venture to say that the risks there will not be different from elsewhere,” he said.

Castro and his colleagues suspect that--consistent with the evidence nationally that AIDS is transmitted sexually or by an interchange of blood--the large number of female prostitutes who cater to the male farm laborers in the area may be a good part of the explanation. Of the 41 cases reported to date, 15% are female, twice the national rate.

MacLeod and Whiteside agree that AIDS may be transmitted heterosexually. But they contend that mosquitoes also are playing a role, either by transmitting the AIDS virus from one person to another by bites, or by carrying certain other viruses that act as co-factors to activate the AIDS virus in bitten individuals.

The two physicians point out that the incidence of AIDS in Central Africa and Haiti in persons who belong to no known high-risk group is also high. And because these regions are mosquito-infested and have a high incidence of viral diseases that are mosquito-borne, the physicians believe that there is a link between AIDS, mosquitoes and the prevalence of certain mosquito-borne viral diseases.

It is well established that mosquitoes do carry certain viruses, called arboviruses, that cause diseases such as yellow fever, dengue fever and St. Louis encephalitis. There is also tentative laboratory evidence that certain arboviruses are capable of activating a special type of virus called a retrovirus, of which HTLV-III is one.

But, said Dr. Thomas Monath, CDC’s expert on arboviruses, it is conceivable that an infection by any virus, not just a mosquito-borne one, could determine whether the AIDS virus becomes activated.

He agrees that there is a clear difference between what is happening in Belle Glade and in the rest of the United States, as well as a correlation with what is happening in Central Africa. But Monath offers several additional arguments against implicating mosquitoes.

Small Volume of Blood

Even in known mosquito-borne viral diseases, not every mosquito carries the virus, he said. Because HTLV-III is not found in large concentration in blood, and because the volume of blood that a mosquito is capable of carrying is very small, he believes that it would take “thousands or millions” of bites in order to transfer an infectious dose of the AIDS virus.

“Theoretically, any mosquito could carry any virus, but the possibility for a mosquito to carry AIDS is extremely low,” he said.

Monath said that to his knowledge no one has ever dissected Florida mosquitoes to see whether HTLV-III is present. But Monath said he now plans to study Culex pipiens, a Florida household mosquito.

Because certain other insects withdraw a larger amount of blood than mosquitoes when they bite, he is using African bedbugs in laboratory experiments to determine the amount of virus that can be present and the amount that is transmitted in a bite.

“If we can show in the lab (that these things are possible), we intend to collect bugs from Belle Glade and Central Africa to test for the presence of virus,” he said.

MacLeod and Whiteside have already studied blood samples from Belle Glade residents to see whether the AIDS cases have more antibodies against arboviruses than do residents who are infected with the AIDS virus but have not developed symptoms of the disease.

Higher Levels Reported

They recently reported that AIDS patients do have higher levels of arbovirus antibodies, an implication that the arboviruses are somehow involved.

Monath has done a similar study, using a different method of testing for antibodies; and he concluded that the level of arbovirus antibodies in the AIDS patients is slightly lower than in the other group.

MacLeod and Whiteside are co-directors of the nonprofit Institute of Tropical Medicine in North Miami. The two physicians became interested in the Belle Glade problem while serving in Belle Glade one day a week as consultants to the Palm Beach County Health Department.

Also expressing skepticism that mosquitoes play a role, Dr. Harold Jaffe, co-director of the AIDS Task Force at CDC, reasons that the absence of cases in children and in other residents who live outside the city’s ghetto area--both of whom could expect to be bitten--again points a finger at a mode of transmission that is sexual rather than mosquito-borne.

Nevertheless, the February study will look for antibodies to 10 types of arboviruses in the human blood samples, including a group called Bunyamwera, which MacLeod and Whiteside believe is especially involved in triggering the AIDS virus.

Regardless of why the disease strikes harder here than elsewhere, the national attention the city has received because of AIDS is doing wonders to improve the housing.

County Takes Interest

A 1979 study showed 49% of the city’s housing to be substandard--16% of it in a dilapidated state. But, local citizens say, little attention was paid to correcting the problem until last year when Palm Beach County finally became interested.

And as a result of a 1980 suit by Rural Legal Services, the city is under a federal court order to demolish the substandard housing which, according to Allan Schnier, the county’s director of housing and community development, amounts to about 3,000 units.

The problem, however, has been finding the money to build replacement units. The county had estimated that it would cost $66.5 million to replace the substandard housing, including some additional housing in nearby Pahokee and South Bay.

Then, last September, the county commissioners finally set aside $5 million a year for two years from county property taxes to go toward the project. Schnier said additional private funding will come from developers who have already expressed interest in the renewal project. County officials also have applied for a $13-million grant from the U.S. Department of Housing and Urban Development.

“It’s AIDS that got things going,” Schnier said. “Without AIDS we might not even have gotten an audience with HUD.”