October 2, 2008
HIV has existed among human populations for about 100 years, decades earlier than previously believed, according to a study published Wednesday in the journal Nature, the Los Angeles Times reports (Engel, Los Angeles Times, 10/2). HIV/AIDS was not recognized formally until 1981, and scientists previously estimated its origin at around 1930. However, the new study, led by Michael Worobey of the University of Arizona, found the origin of HIV to be between 1884 and 1924, with a more focused estimate at 1908. Worobey said that the new result "is not a monumental shift, but it means the virus was circulating under our radar even longer than we knew" (Ritter, AP/Google.com, 10/1).
The research is based on lymph node tissue from an HIV-positive woman who died in the Democratic Republic of the Congo in 1960, then the Belgian Congo. The tissue specimen was one of more than 800 preserved in ice-cube-size blocks of paraffin at the University of Kinshasa. The researchers compared that sample with modern HIV strains to determine its mutation rate. They then matched that rate with the oldest sample of the virus -- from a 1959 blood sample taken from a man who also lived in the Belgian Congo -- and traced their common ancestor to between 1884 and 1924, which represents the first appearance of the virus in humans before it mutated (Los Angeles Times, 10/2). "Those old sequences helped calibrate the molecular clock, which is essentially the rate at which mutations accumulate in HIV," Worobey said, adding, "Once you have that rate, you can work backward and make a guess of when the ancestor of the whole pandemic strain of the AIDS virus originated. It is that ancestor we are dating to 1908 plus or minus about 20 years" (Steenhuysen, Reuters Africa, 10/2).
Worobey said that further research is unlikely to determine that the spread of HIV began any earlier than the late 19th century. "I think we're pretty close to where's it's going to end up. It's possible but unlikely we'd find some branch on the evolutionary tree that went deeper," he said (Innes, Arizona Daily Star, 10/2).
Reprinted with permission from kaisernetwork.org. You can view the entire Kaiser Daily HIV/AIDS Report, search the archives, or sign up for email delivery at www.kaisernetwork.org/dailyreports/hiv. The Kaiser Daily HIV/AIDS Report is published for kaisernetwork.org, a free service of the Kaiser Family Foundation, by The Advisory Board Company. © 2008 by The Advisory Board Company and Kaiser Family Foundation. All rights reserved.