Sociogenic illness is a term that is used to describe a medical condition that spreads within a social group, but does not seem to have a common organic cause. Sociogenic illnesses may be psychosomatic in nature resembling a mass hysteria, or may be defined by individuals with disparate illnesses that are wrongly linked to a common cause.

Two examples of sociogenic illness widely publicised by the media are as follows:

• An incident involving a cancer patient, Gloria Ramirez
  Gloria Ramirez
  Gloria Ramirez was a Riverside, California, woman dubbed "the toxic lady" by the media when several Riverside General Hospital workers became ill after exposure to her body and blood...
  
  , in California on Feb 19th, 1994. Ramirez was brought into Riverside General Hospital's ER by paramedics after experiencing chest pain and stomach upset. After drawing blood from the patient, hospital staff began to faint after noting an ammonia-like smell. Staff attended to the fallen medical staff and attempted to treat Ramirez, who died shortly after. The ER was evacuated, and after searching for a toxin, none was found. A State study of the incident concluded Mass Sociogenic Illness as the cause but could not however rule out study the possibility that some workers were exposed to a poisonous substance (believed to be dimethyl sulfate
  Dimethyl sulfate
  Dimethyl sulfate is a chemical compound with formula 2SO2. As the diester of methanol and sulfuric acid, its formula is often written as 2SO4 or even Me2SO4, where CH3 or Me is methyl...
  
  ). The study stated that both the source of the exposure and the nature of the compound could not be determined. This study neglected to interview key witness such as medical personnel with continuing and serious health problems. This case is still a mystery and a toxin/poison was never found. (New York Times)

• A possible outbreak of mass sociogenic illness in Belgium in June, 1999 when people, mainly schoolchildren, became ill after drinking Coca-Cola. In the end, scientists were divided over the scale of the outbreak, whether it fully explains the many different symptoms and the scale to which sociogenic illness affected those involved. (Source: http://www.pubmedcentral.nih.gov)

The examples above attest to the fact that sociogenic illness is difficult to determine and diagnose. It occurs under circumstances that are often complex and involving many factors.