Prevention of nosocomial transmission of norovirus by strategic infection control measures

BACKGROUND. Nosocomial outbreaks of norovirus infection pose a great challenge to the infection control team. METHODS. Between November 1, 2009, and February 28, 2010, strategic infection control measures were implemented in a hospital network. In addition to timely staff education and promotion of directly observed hand hygiene, reverse-transcription polymerase chain reaction for norovirus was performed as an added test by the microbiology laboratory for all fecal specimens irrespective of the request for testing. Laboratory-confirmed cases were followed up by the infection control team for timely intervention. The incidence of hospitalacquired norovirus infection per 1,000 potentially infectious patient-days was compared with the corresponding period in the preceding 12 months, and the incidence in the other 6 hospital networks in Hong Kong was chosen as the concurrent control. Phylogenetic analysis of norovirus isolates was performed. RESULTS. Of the 988 patients who were tested, 242 (25%) were positive for norovirus; 114 (47%) of those 242 patients had norovirus detected by our added test. Compared with the corresponding period in the preceding 12 months, the incidence of hospital-acquired norovirus infection decreased from 131 to 16 cases per 1,000 potentially infectious patient-days (P< .001), although the number of hospitalacquired infections was low in both the study period (n=8) and the historical control periods (n=11). The incidence of hospital-acquired norovirus infection in our hospital network (0.03 cases per 1,000 patient-days) was significantly lower than that of the concurrent control (0.06 cases per 1,000 patient-days) (P=.015). Forty-three (93%) of 46 norovirus isolates sequenced belonged to the genogroup II.4 variant. CONCLUSIONS. Strategic infection control measures with an added test may be useful in controlling nosocomial transmission of norovirus.