The year 1981 was the first time AIDS was openly recognized as an infectious disease. By the time it was discovered, thousands of people had been infected as the virus circulated under the radar. Now, scientists from the University of Cambridge and the University of Arizona have traced the most common North American strain of HIV, the virus that gives way to AIDS, to when it arrived in the United States and how it spread across the country.
The study clears the name of Gaetan Dugas, a gay flight attendant, dubbed Patient 0 for having supposedly introduced the AIDS virus to the U.S.
The scientists studied viral RNA from eight HIV infected individuals to find a common ancestor of the virus. They were able to date the entry of HIV into the U.S. to the years 1970 or 1971. The researchers further traced the entry of the virus in New York City from the Caribbean; it later spread from New York City to the rest of the East Coast and San Francisco.
A decade went by before the presence of the disease was detected by doctors, which gave it plenty of time to diversify and spread.
“Even though the samples come from the late 1970s, an early time point long before anyone noticed AIDS, nevertheless, the samples contain … so much genetic diversity that they could not have arisen from the late 1970s,” says Michael Worobey, the lead author of the study published in Nature in a press conference Tuesday.
“It’s kind of direct evidence of many years of circulation of this virus in the United States before HIV and AIDS were finally recognized.”
Once the virus reached the United States, it spread rapidly – the researchers calculated that the number of people infected more than doubled every year on average. Because HIV tends to remain latent for years before giving way to AIDS, it remained under the radar for years.