[Noroviruses are the most common pathogens causing nosocomial gastroenteritis outbreaks in Hungarian hospitals]

Norovirus (genera; previously "Norwalk-like viruses") of the family Caliciviridae are an important cause of acute gastroenteritis outbreaks. Epidemics commonly occur in crowded community and spread by fecal-oral route through contaminated food, water and direct contact.

To determine the incidence and epidemiological role of caliciviruses in nosocomial gastroenteritis outbreaks in hospitals in Hungary.

Between November 1998 and April 2002, 277 stool samples of 39 nonbacterial hospital outbreaks reported as "enteritis infectiosa" with unknown etiology from 13 of 19 counties in Hungary were examined by reverse transcription-polymerase chain reaction (RT-PCR) for Norovirus and Sapovirus and by a new recombinant enzyme immune assay (rEIA) for Norovirus only.

99 (36%) of 277 stool specimens were positive by RT-PCR and 29 (74%) and 38 (97%) of 39 outbreaks were positive by RT-PCR and RT-PCR and/or rEIA for Norovirus, respectively. Norovirus were the most frequently detected agents in the registered nosocomial enteric hospital outbreaks in years 2000 (n = 4; 31%) and 2001 (n = 7; 23%). In the first 4 months of 2002, 25 (66%) of 38 nosocomial outbreaks was caused by Norovirus. Seventeen (44%) outbreaks occurred in single internal wards and eight (21%) in more than one (2-8) ward. An average of 32% (0-80%) of the sick persons, were member of the hospital staff. Twenty four (63%) Norovirus-associated outbreaks occurred between January and March 2002.

This is the first comprehensive country-wide surveillance of nosocomial gastroenteritis outbreaks in hospitals associated with Norovirus. Data showed that Norovirus were the most important cause of these outbreaks in Hungary but the epidemiological role of this virus is probably further underestimated.