[Outbreaks of norovirus gastroenteritis in nursing homes in Haifa, 2002-2003].

Background: The incidence rate of Norovirus gastroenteritis is unknown since diagnostic tests are less readily available than for other agents. This pathogen is identified in less than 10% of acute gastrointestinal illness, despite the fact that recent reports from the United States attribute more than 50% of outbreaks to Noroviruses.

Objectives: This article describes three outbreaks of gastroenteritis caused by Noroviruses in three of Haifa's chronic care hospitals in order to raise awareness of its main role as a common agent in such outbreaks, and thereby include it in the differential diagnosis of outbreak investigations.

Methods: Methods employed included epidemiological investigation of the outbreaks, sanitary inspection, personal interviews of hospital staff members, data collection from medical files and laboratory diagnosis by electron microscopy and RT-PCR of stool and vomitus for Noroviruses.

Results: Noroviruses were identified in faeces and vomitus of patients in 2 outbreaks in chronic care hospitals in Haifa. Attack rates were high (20-41%). Proximity in time to these 2 outbreaks, and clinical and epidemiological findings lead us to attribute another outbreak in a third hospital to norovirus as well.

Conclusions: Physicians in institutions and the community should include Noroviruses in the differential diagnosis of outbreaks of gastroenteritis, particularly in cases where no other pathogens have been isolated. Timely requests for identification of Noroviruses are essential. The institution of good hygienic practices is important to prevent spread of this highly infectious agent.