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Loretta McLaughlin
A PROMISING new way to prevent the spread of HIV is being tested in Botswana on a group of people who are being exposed to a particularly vicious strain of the virus. They are now being treated with strong antiretroviral drugs.
The “test and treat’’ approach is not primarily intended to ward off the development of full blown AIDS, though it should also do that. Rather, the purpose of the trial is to sharply reduce the high quantity of virus being generated in an infected person to such a low level that little to no HIV would be available to pass along to a partner.
This new means of prevention was designed and is being employed by AIDS scientists from the Harvard School of Public Health in the village of Mochudi, where 25 percent of the adult population is infected with HIV-1C. This strain causes the amount of virus in a person’s system to climb steeply and remain high for a long time, magnifying the risk of infecting others.
Customarily, strains of HIV cause individuals to build high viral loads - and be highly infectious - for a few weeks or months. Then the body’s immune system brings the viral load under control. When the quantity of virus drops, the risk of transmission also drops and usually stays low for a number of years.
But the HIV-1C virus in southern Africa causes “high viral loads that are prolonged for up to two years after infection in some of the people,’’ according to Max Essex, chairman of the Harvard AIDS Initiative and the Botswana-Harvard partnership. This, of course, means victims are likely to be “hypertransmitters’’ - people much more likely to be able to transmit the infection and do so for a much longer time than carriers of other strains of HIV, such as those that are dominant in the United States and Europe.
Essex considers new forms of prevention as essential to bringing the AIDS pandemic under control. Some 3 million people a year become infected with HIV worldwide.
Until now the weapons of prevention have been abstinence, condom use during every sexual encounter, constant availability of clean drug-injecting apparatus, universal use of medicines to prevent passing the virus to a developing fetus during pregnancy, and, relatively recently, adult male circumcision.
Fortunately, through projects over the past decade from Harvard’s AIDS Initiative and with the strong support of Botswana’s former president, Festus Mogae, the means and manpower are at hand to test the hypothesis that rapid treatment with anti-HIV medicines will prove to be an important new way to prevent spread of the infection.
To conduct the trial, the 23,000 adults in Mochudi will be tested not just for infection with HIV but to detect high viral loads. A cadre of local health workers will go house to house to do the testing. Villagers found to have high quantities of virus, and who agree to do so, will be immediately placed on proven antiretroviral drugs.
The “test and treat’’ program also will apply new genetics tests to map how HIV-1C spreads within a community. DNA from a simple blood spot now can be genetically analyzed to pinpoint who infected whom within the village. This should show whether people with new infections band together in “transmission clusters’’ and thereby provide a clearer focus for future prevention efforts
The degree of success or failure of the trial of early medical treatment as a form of prevention can be known within a couple of years. Though testing will be repeated every six months, it must continue for about two years after the prevention drugs are first used to get statistically valid results. A decline in new infections will show whether the method works.
By targeting therapy to the most highly infectious it seems possible to significantly reduce the rate of new infections in others not only in a village, but also in larger populations - potentially whole nations - where a common HIV strain is dominant.
Loretta McLaughlin, former Globe editorial page editor, is a senior fellow at the Harvard AIDS Initiative. 
© Copyright 2010 Globe Newspaper Company.
