Scientists have confirmed the existence of an additional strain of HIV that has been around for decades, according to findings published Wednesday in the Journal of Acquired Immune Deficiency Syndrome.
The strain is not new; rather, what's changed is the technology used to study the virus.
"The subtype has been around as long as all the other strains have. We just didn't recognize it as an official subtype until now," said Mary Rodgers, author of the new study and principal scientist of infectious disease research for Abbott Laboratories.
HIV, or human immunodeficiency virus, is the virus that causes AIDS if not treated early and appropriately.
The Centers for Disease Control and Prevention estimated 36.9 million people worldwide were living with HIV in 2017. That included 1.1 million people in the U.S. Of those, the CDC estimated that about 14 percent were unaware they had HIV.
The newly recognized strain is classified as subtype L in the group M family of HIV-1. The "M" stands for "major" because it's responsible for more than 90 percent of HIV infections worldwide.
Because that family of viruses is so pervasive, experts believe drugs already used to control HIV would work for subtype L, too. There is no reason to believe this subtype is more dangerous or virulent than any other strain of HIV.
"I would expect it to respond to treatment the same way those other strains do," Rodgers told NBC News. "I don't think there's any cause for concern."
There are 10 different subtypes in the group M family. Subtype L was first identified in 1983, and then seen again in 1990, both in Democratic Republic of Congo. It was found a third time in 2001, also in Congo.
But it's taken this long for the technology used to sequence the subtypes to improve. Now scientists are able to test the entire genome to confirm the samples were all part of the same subtype.
This is important because it helps scientists accurately detect the wide variety of HIV strains in circulation globally, Rodgers said. That, in turn, helps to prevent outbreaks that could arise from viruses that may have mutated.
"The whole point of what we're doing," said Rodgers, "is to make people feel safe."