HIV is not becoming more virulent over time, according to a French study published online May 6 in AIDS and reported by aidsmap. These results contrast with those of a U.S. study first reported at a conference in October 2008 and published earlier this month in The Journal of Infectious Diseases.  

Given HIV’s ability to rapidly mutate, and the fact that viruses can evolve to become more or less virulent over time, it has always been a concern that HIV could become more dangerous as time passes. A recent study reported by Nancy Crum-Cianflone, MD, of the University of California in San Diego (UCSD) and her colleagues suggested this was occurring, at least in the United States. According to her group’s reports, the average CD4 cell counts among people newly infected with HIV have consistently dropped over the years, indicating HIV is becoming more virulent and leading to more rapid disease progression.

To explore this further, Pénélope Troude, MD, from the Institut National de la Santé et de la Recherche Médicale (INSERM) in Le Kremlin-Bicêtre, France, and her colleagues examined the medical records of 903 HIV-positive patients in the PRIMO Cohort study. The patients were all enrolled within six months of becoming infected between 1997 and 2006. Most of them were male and Caucasian, averaging 35 years of age. Because factors such as sex, age, race and HIV subtype can all influence CD4 count and viral load after infection, Troude and her colleagues controlled for these factors in their analysis.

Troude’s team found that the average CD4 count, viral load and HIV DNA levels after infection remained stable during the nine years of analysis, provided that they controlled for changes in factors known to affect these levels. For instance, women tend to have higher CD4 counts and lower viral loads than men after infection. Because the proportion of men increased over time in the study, it would have seemed that both of these measures were becoming worse as the years passed if sex had not been taken into account.

The French authors believe their study is the most thorough of all studies conducted so far looking at changes in HIV virulence over time. At the same time, they stress the need for further studies in other large cohorts to confirm their results.

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