Rapid molecular detection of influenza outbreaks in nursing homes.

摘要

BACKGROUND: Nursing home influenza outbreaks occur in spite of established vaccination programs, and require rapid and sensitive laboratory confirmation for timely intervention. OBJECTIVES: To evaluate diagnostic approaches for rapid confirmation of nursing home influenza outbreaks. STUDY DESIGN: Influenza virus real-time PCR and Directigen Flu A+B enzyme immunoassay were performed on nasopharyngeal swabs, nasopharyngeal washes and throat swabs collected from residents with clinical suspicion of influenza during seven probable nursing home outbreaks in 2004-2005 and 2005-2006. The efficacy of specimen sampling and transport management by Public Health Service outbreak team was evaluated. RESULTS: PCR detected influenza RNA in 80% (68/85) of specimens from 81% (38/47) residents, confirming six suspected outbreaks. Immunoassay sensitivity was highest on nasopharyngeal swabs (38%; 11/29) with a positive predictive value of 100% compared to PCR. Nasopharyngeal swabs were equally sensitive to nasopharyngealwashes by PCR. Nasopharyngeal wash sampling appeared unpractical due to common underlying disability of residents. Outbreak team support was associated with a shorter time to PCR diagnosis compared to outbreaks with no logistical support (mean, 28.2h vs. 84h; P=0.05). CONCLUSIONS: Influenza real-time PCR on nasopharyngeal swabs, obtained by Public Health Service outbreak teams, enabled rapid and sensitive confirmation of nursing home influenza outbreaks.