An Outbreak of Norwalk Gastroenteritis Associated With Swimming in a Pool and Secondary Person-to-Person Transmission

Abstract

In June 1977 an outbreak of acute gastroenteritis affected 103 students and teachers at an elementary school in Ohio. The illness typically lasted 24 hours or less and was characterized by vomiting (86%) and cramping (70%), but more than half of the persons involved also reported having nausea, diarrhea, and headache. Similar illness frequently followed in household members (29%) of families with primary cases. Investigation revealed that 70% of the children and teachers who swam in a pool at an all day outing June 1 (4 classrooms) and 55% of those who swam during a similar outing June 2 (2 classrooms) had the onset of acute illness from 12--48 hours later. None of the children who attended the outings but did not swim had a similar illness. The evidence suggested that the primary outbreak was caused by contaminated water in the pool and that person-to-person spread of illness followed. Results of a microbiologic study of pool water were negative for bacterial and viral pathogens. Throat washings, stool specimens, and paired blood samples studied for evidence of pathogens were negative initially, but subsequent serologic studies suggested that infection by Norwalk virus was the cause of the outbreak. The pool chlorinator which was inadvertently unconnected at the time of the school visits was reconnected and an underground leak in the water supply pipes was corrected. No more cases were reported after the pool was drained, cleaned, and reopened.

Outbreaks of food-borne and waterborne viral gastroenteritis

“…In several studies, the number of patients with significant antibody titer rises was apparently reduced by the collection of acute-stage sera a week or more after onset of symptoms (4,77). However, in these and other studies, geometric mean antibody titers in convalescent-stage sera were greater in patients than in controls, supporting the conclusion that Norwalk virus was the cause of the outbreak (43,72,75,82,111).…”

“…Outbreaks of Norwalk virus gastroenteritis have been associated with swimming in lakes and swimming pools (4,15,72,74). These outbreaks typically occur during summer months in the United States.…”

Pathogenic Human Viruses in Coastal Waters

“…Norwalk-like viruses (also called small round structured viruses) have been identified in drinking water (72,84,85), recreational water (73), and marine shellfish (81) tissue in a number of studies investigating their role in human disease (25,29,50,55,90). This diverse group of RNA viruses often causes gastroenteritis with diarrhea and/or vomiting, fever, and respiratory symptoms lasting approximately 2 days.…”

An outbreak ofEscherichia coliO157 associated with a children's paddling pool

“…Outbreaks due to a wide range of enteric infections such as giardiasis [10][11][12], cryptosporidiosis [13,14], Norwalk gastroenteritis [15], hepatitis A [16] and enterovirus-like illness [17] have been reported in association with swimming pools and other communal water play areas. Experimental work following a major waterborne outbreak in Missouri, USA in 1991 has demonstrated the ready survival of E. coli 0157 in water for a week at temperatures of 5°C and 20°C [6].…”