Origins of the HIV epidemic

Beginning around 1979, doctors in Los Angeles, San Francisco, and New York began noticing a series of unusual and debilitating infections in young, gay men. The most life-threatening and surprising of these illnesses were a formerly rare pneumonia called Pneumocystis pneumonia (PCP) and a cancer known as Kaposi's sarcoma. A range of other severe protozoal, fungal, bacterial, and viral infections had also been detected amongst previously healthy men. In many cases, doctors had begun to find persistently swollen lymph glands.

A report on five PCP cases in Los Angeles appeared in the 5 June 1981 Morbidity and Mortality Weekly Report (MMWR). This bulletin, published by the CDC (Centers for Disease Control, now Centers for Disease Control and Prevention) was seen as a fast and efficient way to spread the news about a new outbreak, as MMWR is widely distributed nationally and internationally to hospitals, healthcare agencies, and infectious disease specialists. 

One month later, the first official account of Kaposi’s sarcoma (in 26 patients in New York and Los Angeles) appeared in the 4 July 1981 MMWR, accompanied by news of an additional ten cases of PCP. The epidemic was out in the open and alarming to those few who heeded the news.¹

By late 1981, researchers were beginning to link these and other opportunistic infections to immune system damage. Many of the patients had significantly altered ratios of CD4 T-cells (also known as 'T-helper cells') to CD8 T-cells ('cytotoxic cells'). This balance, an essential component of the immune system, helps the body fight infection. In 1982, the CDC acknowledged there was an epidemic in the US and it was called 'acquired immune deficiency syndrome' (AIDS).

PCP is now recognised as a distinct form of Pneumocystis carinii and is called Pneumocystis jirovecii.