Norovirus – UK (02): (Scotland), Open water swimmers, comment
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Date: Mon 23 Jul 2012
From: Niklas Danielsson <Niklas.Danielsson@ecdc.europa.eu>
Outbreaks of norovirus (NV) infection have been linked to recreational fresh water activities before [1, 2], and such outbreaks are likely to be more common than previously recognised. A large NV outbreak with more than 400 cases in the southwest of Sweden in 2004  associated with swimming in lakes was investigated for risk factors for developing symptomatic infection.
The risk of disease was found to be associated with several exposures, including the time spent in the water, accidental ingestion of water, and the presence of public toilets close to the place of swimming. This outbreak was not preceded by large rainfalls, but temperatures and the number of people swimming in the lakes were high. A coincidental routine water sample taken from one of the implicated lakes on the 2nd day of the outbreak was positive for NV.
 Outbreak of norovirus in Västra Götaland associated with recreational activities at two lakes during August 2004. Sartorius B, Andersson Y, Velicko I, De Jong B, Läfdahl M, Hedlund KO, Allestam G, Wöngsell C, Bergstedt O, Horal P, Ulleryd P, Soderstrom A. Scand J Infect Dis. 2007;39(4):323-31.
Norwalk gastrointestinal illness: an outbreak associated with swimming in a recreational lake and secondary person-to-person transmission. Baron RC, Murphy FD, Greenberg HB, Davis CE, Bregman DJ, Gary GW, et al. American Journal of Epidemiology 1982;/115:/163-72.
Senior Expert Communicable Diseases, The Epidemic Intelligence Section, European Centre for Disease Prevention and Control (ECDC) Niklas.Danielsson@ecdc.europa.eu
ProMED-mail thanks Niklas Danielsson for drawing attention to these publications.
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Norovirus - UK: (Scotland), open-water swimmers 20120722.1210889