Human immunodeficiency virus—the virus that causes AIDS—is evolving.
This fact isn’t new. Sometime in the early 1900s the virus gained the ability to jump from its original primate host to a new one: humans. In the process HIV became a global agent of infection that cripples the immune system. It continues to evolve and dodge the drugs we use to combat it.
But now researchers suspect that HIV’s changes may actually a boon to humankind, for once. These change may be making the virus slower, in a way.
A new study based in Botswana and South Africa shows that HIV infection is taking longer to develop into AIDS, in part because the virus is becoming less able to cause disease, reports Kate Kelland for Reuters.
More than 2,000 women with HIV participated in the study, which sought to understand how the evolution of human resistance to the virus is influencing the epidemic. Some people carry alleles, or gene copies, that give them some protection against HIV. But in Botswana, where the epidemic started earlier than in South Africa, those protective alleles have been out-evolved by HIV. This kind of constant arms-race of evolution makes understanding the epidemic complicated.
The researchers found that the same one-upmanship that let HIV overcome to protective allele’s effect also made the virus replicate slower, they report in the Proceedings of the National Academy of Sciences. In other words, HIV was becoming less virulent.
"It is quite striking," study author Philip Goulder of Oxford University told BBC.com. "You can see the ability to replicate is 10 percent lower in Botswana than South Africa and that's quite exciting."
The development’s speed is surprising, but the fact that it's happening at all is not so strange, explains Tom Chivers for The Telegraph. "We tend to think of viruses and bacteria as trying to harm us, and with that perspective it's easy to assume that they'll evolve to get better at doing that," he writes. "But in fact, all any pathogen is 'trying' to do is survive and reproduce." Viruses that make their hosts sick enough that they stay in bed or kill them outright aren’t actually surviving and reproducing very well. The common cold, conversely, is a very successful virus because people still go to work, sneeze, cough and spread it around.
The new finding may help explain why, for the first time, the number of new HIV infections is lower than the number of HIV positive people new to receiving treatment—a ratio that indicates "a crucial tipping point has been reached in reducing deaths from AIDS," reports Kelland for Reuters.
The slower-to-reproduce HIV isn’t the only factor. Anti-HIV drugs are still helping keep to infections more controlled and to slow the development of AIDS. While theoretically it’s possible that HIV could evolve to a more harmless version of itself, it still is and will remain for some time a deadly disease. "[It] would be overstating it to say HIV has lost its potency -- it's still a virus you wouldn't want to have," Goulder told Reuters. Research and a global effort to beat the epidemic are still needed.