Co-circulation of human metapneumovirus and SARS-associated coronavirus during a major nosocomial SARS outbreak in Hong Kong

BACKGROUND: The clinico-epidemiological significance of human metapneumovirus (hMPV) detected during the SARS outbreak is unknown. OBJECTIVES: To characterize a nosocomial hMPV outbreak during the 2003 SARS epidemic. STUDY DESIGN AND METHODS: All available nasopharyngeal aspirate (NPA) collected from confirmed patients during the first 8 weeks of the SARS outbreak in 2003 were tested for hMPV by a nested RT-PCR assay targeting the F-gene. Clinico-epidemiological information was used to analyze the relationship of hMPV co-infection to specific risk factors (demographics/symptoms/outcomes; status as health-care workers (HCWs)/patients; history of exposure/contact; ward location). Multivariate logistic regression analysis was performed to determine independent risk factors. RESULTS: An hMPV outbreak occurred during 6-16 March 2003 (first week of the Hong Kong SARS epidemic). hMPV RNA was detected in 31 of 155 (20%) NPAs from SARS patients. HCW status (OR 2.72, 95% CI 1.11-6.68; p=0.029) or epidemiological linkage to the SARS outbreak ward (OR 3.59, 95% CI 1.42-9.05; p=0.007) were independent factors associated with hMPV infection. Symptoms of cough and coryza were more common in co-infected individuals (22.6% vs. 15.9%) but this was not statistically significant. Other clinical manifestations and outcomes were not different in co-infected patients. CONCLUSIONS: A major nosocomial hMPV outbreak involving HCWs occurred during the early SARS epidemic. Patients with dual hMPV and SARS infection were not sicker than those with SARS infection only.