A variant of HIV that is faster at progressing to serious illness and more contagious than other versions of the virus has been circulating in the Netherlands for decades, researchers have found.

The findings, which were published in the journal Science on Thursday, demonstrate how HIV can mutate to create more severe disease and more rapid transmission.

The study serves as a reminder – in the age of COVID variants – that viruses don’t always weaken over time. “We should never underestimate the potential for viral evolution,” Joel Wertheim, associate professor of medicine at the University of California San Diego, says. “Let this study stand in stark contrast to the claim that all viruses will inevitably evolve to be benign.” Read more at NPR.