Frequency of outbreak investigations in US hospitals: results of a national survey of infection preventionists.

BACKGROUND A survey of infection preventionists was conducted to determine the frequency of outbreak investigations in US hospitals. METHODS A 2-part electronic survey was sent to Association for Professionals in Infection Control and Epidemiology, Inc, members in US hospitals in January 2010. Part 1 of the survey tool involved hospital demographics and the infection prevention/control program. Part 2 explored specific outbreak investigations allowing responses for up to 8 investigations within the previous 24 months. RESULTS A final sample of 822 responses was analyzed representing 386 outbreak investigations in 289 US hospitals. Nearly 60% of the outbreaks were caused by 4 organisms: norovirus (18%), Staphylococcus aureus (17%), Acinetobactor spp (14%), and Clostridium difficile (10%). Norovirus occurred most often in behavioral health and rehabilitation/long-term acute care units, whereas the other organisms occurred in medical/surgical units. Unit/department closure was reported in 22.6% of investigations and most often associated with norovirus. Outbreak investigations are triggered by unusual organisms, rate above baseline for specific site of infection, and rate above baseline for specific unit. Investigations were most frequently conducted in community/nonteaching hospitals and facilities with 201 to 300 beds. Mean number of confirmed cases was 10; mean duration was 58 days. CONCLUSION Norovirus is emerging as an increasingly common hospital-associated organism causing outbreaks in nonacute settings and may lead to unit/department closures.