An Outbreak of Giardiasis and Amoebiasis at a Ski Resort in Sweden

A large number of tourists contracted gastroenteritis at the end of December 1986 at a ski resort in the north of Sweden. The outbreak was due to the intrusion of sewage in the drinking water reservoir through a spillway overflow connected to the sewer. Sewage polluted the drinking water. One to three days after drinking the polluted water, at least 3,600 persons of 4,000 at risk contracted gastroenteritis. The attack rate was 90%. Giardia lamblia was isolated from 1,480 persons and Entamoeba histolytica from 106. At least 50 persons contracted a double infection with G. lamblia and E. histolytica. G. lamblia cysts were isolated from two points in the water distribution system.