Norwalk-like viruses and drinking water

Prof Christopher Fairley (Melbourne University)
Dr Margaret Hellard
Dr Martha Sinclair
Dr John Marshall (VIDRL)
Dr Scot Bowden (VIDRL)

Funded by: Cooperative Research Centre for Water Quality and Treatment

Norwalk-like viruses (NLV, now renamed as Norovirus) are believed to be the most common causative agent for community gastroenteritis. Faecal specimens collected from individuals participating in the Water Quality Study were analysed for a range of bacterial, viral and protozoal pathogens, however analysis for NLV was not performed due to lack of a practicable and affordable method when the study commenced. The Victorian Infectious Disease Reference Laboratory (VIDRL) has now developed a PCR testing method for the detection and genotyping of these viruses.

Testing of over 700 gastroenteritis faecal specimens has now been completed, confirming that this virus is the single most common cause of gastroenteritis in the community, accounting for about 10% of all cases of gastroenteritis. There was no significant difference between rates of Norwalk virus in real and sham water filter groups, indicating that drinking water is not a significant route of transmission in Melbourne. DNA sequencing of selected NLV isolates has revealed previously unknown relationships to overseas isolates.

In addition, nearly 400 faecal specimens from people without symptoms were tested and no positive specimens were detected, demonstrating that asymptomatic carriage of the virus is rare.

Marshall JA, Hellard ME, Sinclair MI, Fairley CK, Cox BJ, Catton MG, Kelly H and Wright PJ. (2003) The incidence and characteristics of endemic Norwalk-like virus-associated gastroenteritis. Journal of Medical Virology 69 (4), 568-578.

Marshall JA, Hellard ME, Sinclair MI, Fairley CK, Cox BJ, Catton MG, Kelly H and Wright PJ. (2004)  Failure to detect Norovirus in a large group of healthy individuals. Public Health 118: 230-233.