The leading cause of healthcare-associated gastroenteritis outbreaks is a scourge to long-term care facilities and requires stepped up prevention efforts, a new study finds.

Norovirus is a highly contagious virus that can cause vomiting and diarrhea. To track outbreaks in nursing homes, assisted living communities and other long-term care facilities, investigators from the Centers for Disease Control and Prevention merged collected data from U.S. health departments from 2009 to 2018.

During the study period, 50 states, Washington D.C., and Puerto Rico reported more than 13,000 norovirus outbreaks and upwards of 410,000 outbreak-associated cases in long-term care facilities. Outbreak rates appeared to be steady at about four per 100 facilities annually, investigators said. 

Most outbreaks (90%) spread person-to-person and occurred in winter, with 75% occurring in December through March. Residents had higher attack rates, at 29% than staff members, at 11%. And for every 1,000 cases, there were 22 hospitalizations and 2.3 deaths, reported Laura E Calderwood, MPH, of the CDC’s Division of Viral Diseases in Atlanta.

A look at prevalent virus strains revealed that NoV GII-4, the current dominant genotype in the general population, indeed was responsible for most outbreaks in the 4,425 facilities where these data were gathered. 

“LTCFs have a high burden of norovirus outbreaks,” Calderwood and colleagues wrote. “Outbreak surveillance can inform development of interventions for this vulnerable population, such as vaccines targeting GII-4 norovirus strains,” they concluded.

The researchers used data from the Centers for Medicare & Medicaid Services and the CDC’s National Center for Health Statistics to estimate state LTCF counts.

Full findings were published in the journal Clinical Infectious Diseases.