Detection and quantification of airborne norovirus during outbreaks in healthcare facilities.

BACKGROUND Noroviruses are responsible for at least 50% of all gastroenteritis outbreaks worldwide. Noroviruses GII can infect humans via multiple routes including direct contact with an infected person, fecal matter, or vomitus, and contact with contaminated surfaces. Although norovirus is an intestinal pathogen, aerosols could, if inhaled, settle in the pharynx and later be swallowed. The aims of this study were to investigate the presence of norovirus GII bioaerosols during gastroenteritis outbreaks in healthcare facilities and to study the in vitro effects of aerosolization and air sampling on the noroviruses using murine norovirus as a surrogate. METHODS A total of 48 air samples were collected during norovirus outbreaks in 8 healthcare facilities. Samples were taken 1 m away from each patient, in front of the patient's room and at the nurses' station. The resistance to aerosolization stress of murine norovirus type 1 (MNV-1) bioaerosols was also tested in vitro using an aerosol chamber. RESULTS Norovirus genomes were detected in 6 of 8 healthcare centers. The concentrations ranged from 1.35 × 10(1) to 2.35 × 10(3) genomes/m(3) in 47% of air samples. MNV-1 preserved its infectivity and integrity during in vitro aerosol studies. CONCLUSIONS Norovirus genomes are frequently detected in the air of healthcare facilities during outbreaks, even outside patients' rooms. In addition, in vitro models suggest that this virus may withstand aerosolization.