Nosocomial outbreak of norovirus gastroenteritidis with unusual clinical-epidemiological features

Literature reports about Norovirus outbreaks, especially in hospitals, have accumulated in the past years, including patients and health workers.This report describes a small outbreak by Norovirus which occurred in USC Urology with unusual clinical-epidemiological features.The clinical course was unusual, as it presented no vomiting and duration of diarrhoea was unusually long (4-6 days) with the lack of involvement of health workers.The search for the virus was done with immunoassay method RIDASCREEN 2a generation on 11/19 patients (58%) with gastroenteritis symptoms, and 3/11 samples (27%) were positive. The molecular investigation by RT/PCR with diagnostic primers JV12 and JV13 on the polymerase region, carried out at the Istituto Superiore di Sanità, Rome, gave negative results while the RT/PCR using primers GIISKR and GIISKF, which amplify a fragment of the capsid region, was positive in 4/11 samples (36%) showing a correlation of 2/4 samples (50%) with RIDASCREEN immunoassay test. Our observations confirm the usefulness of immunoassay tests and the need to extend the molecular methods using different diagnostic primers. In outbreaks of gastroenteritis the microbiologist should consider the detection of Norovirus in diagnostic routine, as a positive result requires prevention measures to avoid also the spreading by droplets when vomiting is present.