title: Is HIV becoming more virulent? Initial CD4 cell counts among HIV seroconverters during the course of the HIV epidemic: 1985-2007.
abstract: BACKGROUND
  Whether human immunodeficiency virus (HIV) seroconverters have been presenting with progressively lower CD4 cell counts over the course of the HIV epidemic is controversial. Additional data on whether HIV might have become more virulent on a population level (measured by post-seroconversion CD4 cell counts) may provide important insights regarding HIV pathogenesis.
  
  
  METHODS
  To determine whether post-seroconversion CD4 cell counts have changed over time, we evaluated 2174 HIV seroconverters as part of a large cohort study during the period 1985-2007. Participants were documented antiretroviral-naive HIV seroconverters who had a CD4 cell count measured within 6 months after receiving a diagnosis of HIV infection. Multiple linear regression models were used to assess trends in initial CD4 cell counts.
  
  
  RESULTS
  The mean initial CD4 cell count decreased during the study period from 632 cells/mm(3) in 1985-1990 to 553 cells/mm(3) in 1991-1995, 493 cells/mm(3) in 1996-2001, and 514 cells/mm(3) in 2002-2007. During those periods, the percentages of seroconverters with an initial CD4 cell count <350 cells/mm(3) were 12%, 21%, 26%, and 25%, respectively. In the multiple linear model, the mean decrease in CD4 cell count from 1985-1990 was 65 cells/mm(3) in 1991-1995 (P < .001)), 107 cells/mm(3) in 1996-2001 (P < .001), and 102 cells/mm(3) in 2002-2007 (P < .001). Similar trends occurred with regard to CD4 cell percentage and total lymphocyte count. Similar decreases in initial CD4 cell counts were observed among African American and white persons during the epidemic.
  
  
  CONCLUSIONS
  A significant decrease in initial CD4 cell counts among HIV seroconverters in the United States has occurred during the HIV epidemic. These data provide an important clinical correlate to suggestions that HIV may have adapted to the host, resulting in a more virulent infection.
authors.affiliation: TriService AIDS Clinical Consortium, Infectious Disease Clinical Research Program, Uniformed Services University of the Health Sciences, Bethesda, Maryland, USA.
authors.forename: Nancy
authors.initials: N
authors.lastname: Crum-Cianflone
authors.forename: Lynn
authors.initials: L
authors.lastname: Eberly
authors.forename: Yafeng
authors.initials: Y
authors.lastname: Zhang
authors.forename: Anuradha
authors.initials: A
authors.lastname: Ganesan
authors.forename: Amy
authors.initials: A
authors.lastname: Weintrob
authors.forename: Vincent
authors.initials: V
authors.lastname: Marconi
authors.forename: R Vincent
authors.initials: RV
authors.lastname: Barthel
authors.forename: Susan
authors.initials: S
authors.lastname: Fraser
authors.forename: Brian K
authors.initials: BK
authors.lastname: Agan
authors.forename: Scott
authors.initials: S
authors.lastname: Wegner
mesh_terms: D000328:Adult; D018791:CD4 Lymphocyte Count / Q000639:trends; D016516:CD4-CD8 Ratio / Q000639:trends; D005260:Female; D006678:HIV / Q000472:pathogenicity*; D015658:HIV Infections / Q000453:epidemiology* / Q000276:immunology*; D006679:HIV Seropositivity; D006801:Humans; D016014:Linear Models; D018655:Lymphocyte Count / Q000639:trends; D008297:Male; D014481:United States / Q000453:epidemiology; D055815:Young Adult