Q fever in an urban area.

In the summer of 1981 29 patients living in Gwent, South Wales, had Q fever; 20 were diagnosed by routine clinical and laboratory services and 9 were discovered by active case-finding. The date of onset of symptoms spanned a 2-month period. The peak incidence was at the end of June. A case-control study showed an association with one area on the outskirts of Newport. Most patients had no direct contact with farms of farm animals and a common source of infection could not be identified. The most likely explanation of the outbreak was that farm vehicles had disseminated contaminated straw, manure, or dust in the area of Newport adjacent to farmland.