An unexplained illness in West Otago.

An apparent epidemic of undiagnosed illness in a rural general practice was investigated. The aims were to describe the illness, the characteristics of the people affected, and to look for possible causes. The patients were questioned about their symptoms, and both patients and controls matched for age and sex, were questioned about possible aetiological factors. Twenty-eight cases were identified; all but three were less than 45 years of age; there were equal numbers of females and males. The most commonly experienced symptoms were tiredness, mood and sleep disturbances, headache, and joint or muscle pains. Results of the case-control study suggested that pollution of the water supply, zoonotic infections, contact with agricultural chemicals, and self-dosing with selenium were unlikely to be causes of this illness. An unidentified virus was regarded as the most likely cause.