More than 37 million people worldwide have been infected with HIV or AIDS.
Now, a new strain of the virus has been identified.
For the first time in nearly 20 years, a new subtype of the human immunodeficiency virus, or HIV, has been identified.
HIV is the virus that causes AIDS.
The newly identified strain is more like an ancestral strain, and likely circulating in the Democratic Republic of Congo, according to a new study published in the Journal of Acquired Immune Deficiency Syndrome.
Researchers at Abbott Laboratories in Illinois examined the strain, in another specimen collected from the region, as part of separate research on the prevention of HIV transmission from mother to child.
The specimen confirmed the new subtype, and the ongoing transmission of the virus in that part of the world as recently as 2001.
Researchers hope identifying new viruses like this one, will help ensure new pandemics are stopped.