AIDS has been recognized as a disease since 1981, when doctors in Los Angeles reported a cluster of unusual infections in five young men. But the virus that causes it, HIV, has been circulating in humans for far longer. Genetic analysis traces the pandemic strain back to around 1920 in what is now Kinshasa, Democratic Republic of Congo, meaning the virus has been infecting people for over a century.
The Virus Is Older Than the Disease Name
HIV jumped from primates to humans at least 13 separate times. Only one of those crossover events sparked a global pandemic. Researchers at the University of Oxford used genetic data to estimate that the pandemic strain, known as HIV-1 group M, emerged in Kinshasa around 1920, with a confidence window of 1909 to 1930. For roughly 60 years after that, the virus spread quietly through central Africa without anyone knowing it existed.
The oldest confirmed human sample containing HIV comes from 1959. Labeled ZR59, it was recovered in what was then the Belgian Congo. A second early sample, a lymph node from an adult woman, was found in the University of Kinshasa’s pathology archives and dates to 1960. Both confirm that HIV was present in the region decades before anyone connected it to a disease.
The First Cases Doctors Noticed
On June 5, 1981, the CDC published a short report describing five previously healthy men in Los Angeles, all between 29 and 36 years old, who had developed a rare lung infection called Pneumocystis pneumonia. Two of them had already died. All five also had severe fungal infections and signs of a collapsing immune system. Pneumocystis pneumonia was so uncommon in healthy adults that even a small cluster stood out immediately.
Within weeks, similar reports surfaced in New York and San Francisco. Doctors were also seeing a rare cancer called Kaposi’s sarcoma in young men who should have been at extremely low risk. Something was destroying their immune defenses, but no one yet knew what.
From “GRID” to “AIDS”
Because early cases in the U.S. were concentrated among gay men, the press and some researchers initially called the new illness GRID, for Gay-Related Immune Deficiency. The New York Times first used that term in May 1982. But cases were also appearing in people who injected drugs, hemophiliacs receiving blood products, and Haitian immigrants, making it clear the disease was not limited to any single group.
By September 1982, the CDC adopted the name AIDS, short for Acquired Immune Deficiency Syndrome, and published the first formal case definition. That definition described it as any disease indicating a serious breakdown in immune function that occurred without a known cause. The term stuck, and GRID disappeared from use.
Identifying the Virus
The cause of AIDS remained unknown for nearly two years after the first cases. In January 1983, a team at the Institut Pasteur in Paris, led by Luc Montagnier and including virologist Françoise Barré-Sinoussi, received a lymph node sample from a patient in an early stage of the disease. They detected signs of a new retrovirus within two weeks. On February 4, 1983, a microscopist named Charlie Dauguet captured the first photograph of the virus under an electron microscope.
The French team published their findings in the journal Science on May 20, 1983, calling the virus LAV (Lymphadenopathy-Associated Virus). An American team led by Robert Gallo independently identified what turned out to be the same virus, naming it HTLV-III. After a protracted naming dispute, the international scientific community settled on HIV, Human Immunodeficiency Virus, in 1986.
Key Milestones in the Epidemic
The years between the discovery of AIDS and effective treatment were devastating. The first antiretroviral drug, AZT, received FDA approval in March 1987, but it was only modestly effective on its own and came with harsh side effects. It wasn’t until the mid-1990s, when combination therapy using multiple drugs became standard, that survival rates began to improve dramatically.
Global AIDS deaths peaked in 2004. Since then, deaths have fallen by 70%, largely due to wider access to treatment. By the end of 2024, approximately 40.8 million people worldwide were living with HIV, and about 630,000 people died from HIV-related causes that year. Those numbers reflect both the scale of the ongoing epidemic and the enormous progress treatment has made. In the early years, an AIDS diagnosis was essentially a death sentence. Today, people who start treatment early and stay on it can expect a near-normal lifespan.
A Timeline at a Glance
- Around 1920: HIV-1 group M emerges in Kinshasa, crossing from primates to humans.
- 1959: Oldest confirmed human sample containing HIV (Kinshasa).
- June 5, 1981: CDC publishes the first report of unexplained immune failure in five men in Los Angeles.
- September 1982: The term “AIDS” is officially adopted.
- May 1983: French researchers publish the discovery of the virus.
- March 1987: AZT becomes the first approved antiretroviral drug.
- 2004: Global AIDS deaths reach their peak.
- 2024: Roughly 40.8 million people are living with HIV, with annual deaths down 70% from the peak.
So depending on how you frame the question, AIDS has been around for about 45 years as a recognized disease, or the virus behind it has been infecting humans for more than 100 years. The gap between those two numbers explains why HIV had already spread across continents before the medical world even knew it existed.