A norovirus outbreak at a long-term-care facility: The role of environmental surface contamination

BACKGROUND: The role of environmental surface contamination in the propagation of norovirus outbreaks is unclear. An outbreak of acute gastroenteritis was reported among residents of a 240-bed veterans long-term-care facility. OBJECTIVES: To identify the likely mode of transmission, to characterize risk factors for illness, and to evaluate for environmental contamination in this norovirus outbreak. METHODS: An outbreak investigation was conducted to identify risk factors for illness among residents and employees. Stool and vomitus samples were tested for norovirus by reverse transcription polymerase chain reaction (RT-PCR). Fourteen days after outbreak detection, ongoing cases among the residents prompted environmental surface testing for norovirus by RT-PCR. RESULTS: One hundred twenty-seven (52%) of 246 residents and 84 (46%) of 181 surveyed employees had gastroenteritis. Case-residents did not differ from non-case-residents by comorbidities, diet, room type, or level of mobility. Index cases were among the nursing staff. Eight of 11 resident stool or vomitus samples tested positive for genogroup II norovirus. The all-cause mortality rate during the month of the outbreak peak was significantly higher than the expected rate. Environmental surface swabs from case-resident rooms, a dining room table, and an elevator button used only by employees were positive for norovirus. Environmental and clinical norovirus sequences were identical. CONCLUSION: Extensive contamination of environmental surfaces may play a role in prolonged norovirus outbreaks and should be addressed in control interventions.