Norwalk Virus Enteric Illness Acquired by Swimming Exposure

Abstract

In an epidemic of gastrointestinal illness strongly associated with swimming at a recreational park in Macomb County, Michigan, in July, 1979, the authors demonstrated the value of serologic testing to detect Norwalk virus infection. Rises in antibody titer to Norwalk virus were noted in all 11 individuals tested. Electron microscopy on stools from 20 ill individuals revealed only one with Norwalk virus-like particles. This particle was shown by radioimmunoassay and immune electron microscopy not to be Norwalk virus and not to have stimulated detectable antibodies in this individual. These results not only indicate that electron microscopy is insensitive in detecting Norwalk virus, but that it has the potential to mislead. A low rate of respiratory symptoms was associated with gastrointestinal illness in this Norwalk virus outbreak. The route of exposure might have been important for this. The outbreak was also noteworthy in that, although there was evidence of familial clusters of resistance, a very high percentage of the population was proved to be susceptible to the Norwalk virus.

Norovirus

“…This conclusion does not, however, address the 6 subjects who failed to become ill after either the first or second challenge, a finding that suggested the possibility that some individuals are intrinsically resistant to Norwalk virus infection. Five years later, the discovery of familial clustering of infection, with some related groups having apparent resistance, was also observed in a large community outbreak traced to a swimming pool (111). These observations suggested the possibility that some individuals possess inherited protection against norovirus infection.…”

“…The diversity of waterborne sources implicated in norovirus outbreaks ranges widely, indicating the ubiquitous distribution of the virus. Outbreaks have been linked to potable water sources at camps, municipal water systems, commercial ice consumption, and recreational water exposure during rafting and swimming (107)(108)(109)(110)(111)(112). While much of the water contamination is thought to come from discharge of wastewater into rivers, streams, and other bodies of water, the natural distribution of noroviruses in water systems has not been thoroughly explored.…”

Outbreaks of food-borne and waterborne viral gastroenteritis

“…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.…”

A serosurvey of water-borne pathogens amongst canoeists in South Africa

“…The infection is characterized by a short incubation period, acute onset and benign course of illness [32]. Common source outbreaks, with a high attack rate, have been ascribed to the ingestion of faecally contaminated water and ice [33,34], as well as swimming in polluted waters [12,13]. The results of NV seroprevalence studies in this investigation suggest that the canoeists only have a slightly increased chance (age-adjusted POR = 1-34) of acquiring NV gastroenteritis in comparison to the non-canoeists.…”