Did doctors jumpstart the HIV pandemic?

Perhaps it wasn't sex workers and fast-growing cities that launched HIV onto its deadly global rampage, but well-meaning doctors using dirty needles in the first half of the 20th century.

While it's hard to know for sure today, more than 90 years after the virus emerged, two new studies hint that campaigns to eradicate tropical diseases in Africa might have helped HIV gain an early foothold among humans.

"This is sort of an example of good intentions gone wrong," said Dr. Thomas Strickland, an expert in infectious diseases at Baltimore's University of Maryland, who was not involved in the research.

"They were saving lives. They just didn't know that they were also setting up the pandemic of HIV."

The virus jumped from chimps to humans - morphing from simian immunodeficiency virus, or SIV, to human immunodeficiency virus - in central Africa in the early 1920s.

Most likely, scientists speculate, a hunter got infected through a bite or a scratch as he prowled for bush meat and butchered it west of the Ubangi River in what is now the Democratic Republic of the Congo.

What is still a matter of debate is how a blood-borne disease infecting one or a few individuals in a remote area could ever spread to the more than 33 million people who were infected by 2008, and kill two million of them.

To try to answer that question, Dr. Jacques Pepin, of the Universite de Sherbrooke in Montreal, Canada, hopped on a plane to central Africa. His goal was to track the spread of less lethal viruses - as proxies for HIV - among villagers who remembered the colonial era.

For one of two studies published this month, Pepin's team knocked on doors in dozens of villages in the Central African Republic to find seniors who'd been exposed to the sleeping sickness epidemic that ravaged the area between 1936 and 1950.

They asked a bunch of questions of more than 900 villagers, including whether or not they'd been treated for sleeping sickness - at the time a grueling, hard-to-forget series of injections, Pepin said.

The researchers also took blood samples. Because the villagers who first caught HIV would be long dead today, Pepin decided to use the less-deadly hepatitis C virus as well as another blood-borne virus (human T cell lymphotropic virus 1, or HTLV-1) as models for how HIV could have been inadvertently transmitted by the French colonial doctors treating sleeping sickness.

What they found was striking: if a person had been treated for the sleeping disease before 1951, the chances that he or she had been infected with hepatitis C tripled. And HTLV-1 showed a similar pattern.

"What happened is that for a long time, the needles and syringes used to administer the intravenous drugs were not single-use," Pepin told Reuters Health. "There were a lot of patients and not a lot of needles, so the sterilization of needles was not very efficient."