People diagnosed with HIV in 2007 generally had lower CD4 counts than those diagnosed in 1985; it’s a trend, according to a report published in Clinical Infectious Diseases, that suggests the virus may be increasing in virulence, Reuters reports.

According to the article, Nancy Crum-Cianflone, MD, from the Naval Medical Center in San Diego, California, and her colleagues analyzed data from 2,174 patients who tested positive for HIV antibodies and were enrolled in the TriService AIDS Clinical Consortium HIV Natural History Study. None of the study participants received antiretroviral (ARV) therapy, and none had their CD4 counts recorded within six months of their diagnosis.

The average starting CD4 cell counts during the periods 1985–1990, 1991–1995, 1996–2001 and 2002–2007 were 632, 553, 493 and 514 cells per microliter, respectively. During those same periods, the percentage of patients with initial cell counts below 350 cells per microliter were 12 percent, 21 percent, 26 percent and 25 percent.

Reuters reports that these findings are in line with the work of other researchers, who have found that patients in recent years have required ARV treatment sooner following their HIV diagnoses.