a1 Tanzania Family Health Project, P.O. Box 2561, Mbeya, Tanzania
a2 Public Health Laboratory Service, Bridle Path, York Road, Leeds LS15 7TR
a3 Public Health Laboratory Service, Glan Clwyd, District General Hospital, Rhyl, Clwyd LL18 5UJ
In November and December 1992, an outbreak of waterborne cryptosporidiosis occurred in Bradford, a city in the North of England. In all 125 cases were involved, the majority of whom lived in part of the city which received its drinking water supply from a single water treatment works. A case control study demonstrated an association between illness and the consumption of tapwater from this source; those drinking large volumes being more likely to have been ill. Treated water from the defined source yielded cryptosporidial oocysts. Heavy rainfall was recorded in the catchment area of the reservoir supplying raw water to the treatment works, immediately prior to the probable time of infection, based on dates of onset of illness.
(Accepted March 20 1995)