Norovirus Tops List of Hospital Infection Outbreaks

A new national survey on the frequency of infection outbreak investigations in U.S. hospitals found that norovirus was to blame for 18.2% of all outbreaks and 65% of ward closures (Am J Infect Control 2012;40:2–8). The survey's results point to the need to improve communication between clinicians and lab staff to identify outbreaks early, as well as to implement internal policies that guide outbreak investigations.

Researchers from Chartis, Main Line Health System, Lexington Insurance Company, and APIC Consulting Services collected responses from 822 Association for Professionals in Infection Control and Epidemiology members who work in U.S. hospitals regarding outbreak investigations at their institutions during 2008 and 2009. The survey's results reflect 386 outbreak investigations reported by 289 hospitals over a 24-month period.

The survey was aimed at determining how often outbreak investigations are initiated in U.S. hospitals, as well as the causes for investigations, types of organisms, and control measures including unit closures.

Snapshot: Leading Causes of Outbreaks

The authors discovered that four organisms caused roughly 60% of outbreaks: norovirus with 18.2%, Staphylococcus aureus came in a close second with 17.5%, followed by Acinetobacter spp with 13.7%. Clostridium difficile rounded out the list at 10.3%.

New data show that 35% of the 822 hospitals surveyed had investigated at least one outbreak in the previous 2 years. Medical units were the most common location of outbreak investigations, followed by surgical units.

Overall, the survey found the average number of confirmed cases per outbreak to be 10 and the average duration 58 days. Unit closures—reported in 22.6% of cases—involved an average of 16 beds and 8 days per closure.