Apparent declines in the global HIV transmission rate.

Estimates of global and regional HIV incidence and prevalence are helpful for gauging the state of the epidemic. However, they do not contain as much information as the HIV transmission rate for judging the potential speed of HIV spread. The HIV transmission rate can be defined as follows: for every 100 persons living with HIV, the number of HIV infections transmitted to seronegative partners in one year. Here, we estimate the transmission rate for the global epidemic for the years 2001 and 2007, and for 10 major international regions for the year 2007. The transmission rate is calculated as incidence divided by prevalence, and the quotient then multiplied by 100. Previously published and publicly available, the Joint United Nations Programme on HIV/AIDS estimates of HIV incidence and prevalence at the global and regional levels were utilized. Between 2001 and 2007, the global HIV transmission rate dropped from 10.2 to 8.2, a decrease of 19.6% in six years time. The regional estimates for 2007 ranged from 3.7 in Western and Central Europe, to 10.5 in the Middle East and Northern Africa, to 17.6 in Oceania. The global transmission rate for 2007 of 8.2 indicates that 91.8% or more of persons living with HIV are not transmitting to other persons in a given year. The 19.6% decrease in HIV transmission rate between 2001 and 2007 appears to indicate some success in global HIV prevention efforts. The range of regional estimates helps to identify areas with the potential for rapidly growing epidemics, even if the raw numbers of new infections and prevalence are low. I believe the transmission rate to be a useful statistic and recommend its further adoption.