A drug technician at the Centers for Disease Control (CDC) in the USA notices a higher number of requests for the drug pentamidine used in the treatment of pneumocystis carinii pneumonia (PCP).

Dr. Michael Gottlieb at UCLA reports five cases of PCP occurring in Los Angeles gay men.

The search begins for the cause not only of the PCP in gay men in Los Angeles, but also of the Kaposi's Sarcoma (KS) occurring in gay men in New York. The leading candidate for the cause is poppers, or nitrate inhalants. The alternative explanation is that the cause is an infectious agent. Later in the year cases of PCP are recorded in drug addicts.