For the first time in nearly two decades, a new strain of HIV has been identified, according to scientists at U.S. drugmaker Abbott Laboratories. 

Mary Rodgers, a principal scientist at Abbott whose team published their findings on Wednesday in the Journal of Acquired Immune Deficiency Syndromes, said there was no reason for the public to be excessively concerned about the newly discovered HIV subtype, which they believe to be extremely rare. 

But the scientists said the discovery of the new strain — called HIV-1 Group M, subtype L — should serve as a reminder of how diverse and continually evolving HIV viruses are, and how necessary it is for medical and research communities to remain vigilant.

“We can never become complacent, we need to be proactive and we’re working to stay a step ahead of the virus,” Rodgers told the Chicago Tribune. 

“Identifying new viruses such as this one is like searching for a needle in a haystack,” Rodgers added in a statement. “This scientific discovery can help us ensure we are stopping new pandemics in their tracks.” 

There are two different types of HIV and several subtypes. Like other viruses, they can mutate over time. 

The identification of a new HIV subtype “tells us that the HIV epidemic is still ongoing and still evolving,” immunology expert Jonah Sacha, who was not involved in the Abbott study, told Scientific American. 

“The calling card of HIV is its diversity. That’s what’s defeated all of our attempts to create a vaccine,” said Sacha, a professor at the Vaccine and Gene Therapy Institute at Oregon Health & Science University. “People think it’s not a problem anymore, and we’ve got it under control. But, really, we don’t.”