Friday, July 20, 2012

HIV family tree

HIV family tree

Putting the two samples together with dozens of other previously known HIV-1 genetic sequences, the researchers constructed family trees for this strain of HIV.

"Those old sequences helped calibrate the molecular clock, which is essentially the rate at which mutations accumulate in HIV," Professor Worobey said.

"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."

Research from chimpanzee droppings suggests the virus first spread from chimps to humans in south-eastern Cameroon.

Professor Worobey thinks the disease then spread slowly among the local population, until one of the infected people went to Kinshasa, where it had more opportunity to spread.

Professor Worobey thinks by the 1960s, several thousand people may have been infected with HIV.

By 1981, the rest of the world began to recognise the pandemic, which has now infected 33 million people and killed 25 million.

But Professor Worobey sees some hope in the study.

"HIV is one of these pathogens that you could almost think of as living on the edge of extinction," he said.

If it had not been carried to a city, it may not have survived the jump to humans.

"It means there are things we could do to actually make it so that it doesn't have a chance of spreading," Professor Worobey said.

Dr Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, says disease prevention is one of the most important issues in HIV.

"For every one person that we put on therapy, two to three people in the developing world get newly infected," he said.

"The only way we are going to get our arms around this is through prevention."

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