An outbreak of gastroenteritis lasting for one week in August 1980 affected approximately 1,500 persons in a community in northern Georgia. Investigation included a telephone survey of the community, a survey of textile plant employees and junior high and high school students and staff, and a neighborhood door-to-door survey. An association between gastrointestinal illness and consumption of drinking water was shown for community residents, students, and school staff. Attack rates (0-68%) determined in 10 neighborhoods increased significantly (P less than 0.001) with proximity to a textile plant, the site of one of two known cross-connections between an industrial water system (which contained fecal coliform bacteria) and the community water system. A fourfold rise in titer of antibody to Norwalk virus was found in 12 of 19 serum pairs from patients. Norwalk virus illness associated with drinking water from a large municipal water system has not been documented previously. Norwalk virus may be an important cause of waterborne morbidity in the United States.

An outbreak of acute gastroenteritis occurred during January 4-9, 1982, in a rural community in north Georgia. A systematic telephone survey revealed that 63% of persons living in homes served by the community water system had symptoms of acute gastroenteritis in contrast to 9% of persons in homes served by private wells or other sources (P less than .001). A fourfold rise in antibody titer to the Norwalk virus occurred in 20 of 22 serum pairs obtained from ill persons. Fecal coliforms (greater than 16 MPN/100 ml) were detected in a spring which served as one water source for the community system. Surface runoff from a heavy rainfall, which preceded the outbreak, may have contaminated the system. Outbreaks of gastroenteritis should be promptly reported and investigated to facilitate corrective measures and to identify causative agents such as Norwalk virus.