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  7th European HIV Drug Resistance Workshop
March 25-27, 2009
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Viral Loads--But Not Transmission of Resistant Virus--Falling in Italian Cohort
  7th European HIV Drug Resistance Workshop, March 25-27, 2009, Stockholm
Mark Mascolini
Improved antiretroviral regimens and better care greatly lowered the proportion of people with a high or detectable viral load in a large Milan cohort at the L. Sacco Hospital [1]. But that viral load decline from before 2000 to 2006-2007 did not result in a significant drop in proportions of untreated people infected with resistant virus. Transmission of drug-resistant HIV persisted especially among gay men.
Alessia Lai and colleagues analyzed 95,832 viral loads in 4615 potential HIV transmitters seen in five periods: before 2000, 2000-2001, 2002-2003, 2004-2005, and 2006-2007. Viral loads in this group ranged from 1.69 to 6.63 log copies/mL (50 to almost 5 million copies/mL) and CD4 counts from 0 to 1504. Nearly three quarters of this group were male, 39% were infected while injecting drugs, 35% during heterosexual sex, and 23% during sex between men.
The Milan team also charted viral loads in 369 newly diagnosed people, including 103 (28%) recently infected people (seroconverters) with a known date of seroconversion. This subgroup was mostly male (84%), 52% were infected during gay sex, and 44% were infected during sex between men and women. During the five study periods, proportions of people in the overall group with a viral load below 1000 or 50 copies rose significantly (P < 0.0001 for both measures):
• Before 2000: 49.5% below 1000, 10.3% below 50
• 2000-2001: 56.6% below 1000, 28.2% below 50
• 2002-2003: 66.1% below 1000, 42.2% below 50
• 2004-2005, 70.0% below 1000, 52.1% below 50
• 2006-2007, 81.6% below 1000, 66.1% below 50
Transmission of drug-resistant HIV fell over three periods in both newly diagnosed people and recent seroconverters, but these declines did not approach statistical significance:
• 2002-2003: 15.2% (15 of 99 people)
• 2004-2005: 10.9% (15 of 137 people)
• 2006-2007: 11.5% (15 of 130 people)
Among people infected with drug-resistant virus in these three periods, 64.4% of newly diagnosed people and 83.3% of seroconverters were gay men. Transmission of drug-resistant virus fell--again nonsignificantly--in newly diagnosed people from 15.1% to 11.5% and in seroconverters from 22.9% to 12%. Men, Caucasians, and people infected with subtype B virus were more likely to become infected with resistant virus.
The findings show that, at least in this southern European group, controlling HIV better on a population level does not immediately translate into significant declines in transmission of drug-resistant HIV.
1. Lai A, Franzetti M, Violin M, et al. A marked decrease of HIV-1 viremia in a population of potential transmitters in the 1997-2007 interval reduced the proportion of acute seroconverters but minimally affected the transmission of drug resistance. 7th European HIV Drug Resistance Workshop, March 25-27, 2009, Stockholm. Abstract 6.