HIV Transmission in the U.S.

Last year, the CDC revised its estimate of annual HIV incidence in the U.S. from 40,000 to 56,000 new cases per year, based on new testing and statistical methods (JW Aug 19 2008). Now, investigators have used this revised number to estimate the annual rate of HIV transmission in the U.S. They defined that rate as the number of seronegative individuals who acquired HIV in a given year per 100 people living with HIV that year.

Annual transmission rates were highest (>30%) during the explosive growth of the epidemic in the early 1980s and then fell substantially (to 12%–17%) in the late 1980s. From 1991 through 2006, rates were below 10%, and the most recent estimate (from 2006) was 5%.