A non-foodborne norovirus outbreak among school children during a skiing holiday, Austria, 2007

Abstract

Norovirus is increasingly recognized as a leading cause of outbreaks of foodborne disease. We report on an outbreak in Austria that reached a total of 176 cases, affecting pupils and teachers from four schools on a skiing holiday in a youth hostel in the province of Salzburg in December 2007. A questionnaire was sent to the four schools in order to obtain data from persons attending the school trip on disease status, clinical onset, duration of illness and hospitalization. A cohort study was undertaken to identify the sources of infection. The school trip attendees were interviewed by questionnaire or face-to-face on their exposure to food items from the menu provided by the hostel owner. Of the 284 school holiday-makers, 176 fitted the definition of an outbreak case (attack rate 61.9%). A total of 264 persons on the ski holiday participated in the cohort study (response rate 93%). The day-by-day food-specific analyses did not find any food items served on any of five days (December 8-12) of the holiday to be associated with infection risk. The day-specific risk analyses revealed Monday December 10 (RR: 9.04; 95% CI: 6.02-13.6; P < 0.001) and Tuesday December 11 (RR: 3.37; 95% CI: 2.56-4.43; P < 0.001) as the two most risky days for having being exposed to norovirus. According to the epidemiological investigation, airborne transmission of norovirus originating from the first vomiting case most probably initiated this outbreak; foodborne genesis was excluded. During recent years, norovirus has become increasingly established as the most important causative agent of epidemic gastroenteritis in holiday-makers all over Europe. Tourism is one of the primary industries in Austria. Timely involvement of the relevant public health authorities is essential in any outbreak of norovirus gastroenteritis, irrespective of its genesis.

A 2010 Austrian Salmonella enteritidis PT4 outbreak associated with a laying hen holding previously involved in an S. enteritidis PT4 cluster: Pitfalls of regulatory responses in risk management

“…Analysis of the food-specific attack rates by day as described by Kuo et al [13], which considers the time sequence of exposure and disease status, confirmed the spaetzle (at dinner on August 25) at borderline significance and the hamburger (at lunch on August 26) as risk-associated items and additionally identified the potato salad served for dinner on August 26 as a likely infection source for soccer club A, the only club for which the day and time of food exposure were known. The pattern of the outbreak curve for the club A cases, which indicated that the outbreak sources were active on August 25 and 26, agrees with the findings of the day-wise food-specific analyses.…”

Investigating outbreaks: medical imperative or academic indulgence?

“…Austria was one of the first EU member states to pass such a law and routinely comply with it by ensuring epidemiologic and microbiologic investigations of outbreaks of foodborne disease [18]. Several articles published in this issue of Wiener Klinische Wochenschrift [19][20][21][22][23][24] show the great potential of epidemiological outbreak investigations, in Austria as elsewhere, in recognizing sources of infections and their transmission routes. It is important that clinicians recognize this important preventive potential and actively support hospital epidemiologists, health departments and other institutions in the investigation of outbreaks and the necessary control measures.…”

Viral Infections, an Overview with a Focus on Prevention of Transmission

“…Transmission is predominantly by the fecal-oral route. Numerous community outbreaks of norovirus have been reported in restaurants, resorts, cruise ships, schools, and nursing homes (Arvelo et al, 2012;Britton et al, 2014;Kuo et al, 2009;Lai et al, 2013;Wikswo et al, 2011). The emergence of a new variant of norovirus, genogroup II, type 4 (GII.4), in Australia, Europe, and North America associated with increased acute gastroenteritis activity has been reported since 2006 (Bruggink and Marshall, 2010;Hasing et al, 2013;Kanerva et al, 2009;Yen et al, 2011).…”