An outbreak of ornithosis in Norway in 1981.

During 1981 there were 508 laboratory confirmed cases of ornithosis in Norway. This represents a 7-fold increase compared with previous years. Among 370 patients examined by the National Institute of Public Health, Oslo, 148 stated some contact with birds. There were also small family outbreaks and cases of ornithosis in school friends etc. where no bird exposure had occurred, suggesting that interhuman transmission might be involved. The clinical picture was that of a respiratory disease with pneumonia in more than half the cases. The clinical course was mild to moderately severe. At present we have no explanation for this change in the epidemiologic pattern of ornithosis in Norway.