The novelty of the Uganda study was the use of CD4 counts. But there is a caveat: the data come from a single point in time, rather than from following the individuals over a period. And that, Rosen says, introduces the possibility that confounding factors skewed the results. For instance, someone who is proactive in getting tested and obtaining treatment might be a  person who is likely to work more hours a week, anyway.

Even the choice of testing site might make the findings less applicable to other areas, Thirumurthy says. His team sampled a rural population where most adults had access to work through farming. In a large urban setting, such as Johannesburg or Kampala, where unemployment is high across the board, HIV status and CD4 counts might have a weaker correlation with how much a person is able to work.

Nevertheless, Rosen says, all of the recent studies "point to the same conclusion: that treatment is associated with better employment outcomes."

Thirumurthy and his colleagues are currently planning a five-year controlled trial to follow up and study this correlation over time. The trial will study multiple communities, some of which will continue receiving standard care (with treatment starting when CD4 counts dip below 350) and others of which will receive earlier treatment. They will then be able to track whether changes in an individual's CD4 status impacts economic status. These longer studies, Rosen notes, will check whether "starting treatment will forestall some of the negative impacts of [low] CD4 counts on employment." With more detailed data, the researchers should be able to provide more information about long-term health and economic gains of people living longer and potentially working more to measure against the cost of treatment.

A secondary lesson of the work by Thirumurthy and his colleagues was the impressive community response. During the weeklong campaign, 74 percent of the area's adults participated in testing. The program included testing and treatment for HIV as well as other infectious and noninfectious diseases. Nearly half of the people who tested positive for HIV had not previously been diagnosed. With such a large turnout rate, too, Thirumurthy and his colleagues also "were able to learn something about the entire population of HIV-infected adults" in an area, rather than just a subset as in other studies.

"There's so much interest in identifying people early—and possibly implementing early treatment, which is not the national policy yet" in Uganda, Thirumurthy says. Along with recent research showing that treatment can limit the infection's spread, the reasons to start therapy early seem to be growing.

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