Kaposi's sarcoma. How can epidemiology help find the cause?

Kaposi's sarcoma (KS) remains the most commonly diagnosed cancer in AIDS patients. Neither the cause nor a cure for AIDS-related KS is known. KS serves as a striking example of how epidemiologists seek the cause of any disease. Epidemiologic analysis of reported KS cases is revealing but not definitive. The leading hypotheses for the cause of AIDS-related KS are an as-yet-unidentified sexually transmitted infectious agent and exposure to inhalant alkyl nitrites, often called poppers. Epidemiology suggests that persons can reduce their risk of KS by avoiding nitrite inhalants and changing behavior to reduce the risk of sexually transmitted infections.