New Study Traces
Origins of HIV to Turn of the Century

A new study conducted by the University of Arizona in Tucson estimates that HIV has existed in human populations for more than a century.

The study, conducted by evolutionary biologist Michael Worobey, estimates the date of origin at around 1900, which is 30 years earlier than previous analyses. Worobey based his studies on a biopsy sample recently discovered in the Democratic Republic of Congo.

Though HIV-1, the most common strain of the virus, is known to have originated in chimpanzees, tracking its origins has proven more difficult. The first U.S. cases were reported in 1981 when gay men living in urban areas including New York, San Francisco, and Los Angeles began experiencing symptoms doctors thought to be similar to pneumonia. The disease was then named GRID -- gay-related immunodeficiency disease-- and later was called AIDS.

The oldest evidence of the virus is from a 1959 blood sample of a man who lived in what was then the Belgian Congo.

To determine a point of origin, scientists relied on studying the mutation rate of different subtypes of the virus. Upon determining a rate of mutation, scientists then essentially ran the clock backward to determine the point where the different subtypes were the same.

"The HIV virus evolves incredibly quickly," geneticist Bette Korber of Los Alamos National Laboratory in New Mexico, who did an analysis in 2000, told the Los Angeles T imes. "Those mutations get passed on to the next individual. So we have that evolutionary pace to enable a look backward."

Korber's study of the 1959 sample traced a common ancestor back to roughly 1931.

But the latest study added lymph node tissue from a woman who died in the Congo in 1960. The node was one of many preserved in ice cube-size blocks of paraffin at the University of Kinshasa in the Congo.

With that sample, the study's authors were able to trace a common ancestor to sometime between 1884 and 1924, surmising that the establishment of colonial cities in the Congo around the turn of the century allowed the virus to take hold. (The Advocate)