Factors driving norovirus transmission in long-term care facilities: A case-level analysis of 107 outbreaks
Yangping Chen,
Benjamin A. Lopman,
Aron J. Hall,
Anita K. Kambhampati,
Lynn Roberts,
Jordan Mason,
Kelley Vilen,
Ellen Salehi,
Angela Fraser,
Carly Adams
Affiliations
Yangping Chen
Department of Epidemiology, Rollins School of Public Health, Emory University, 1518 Clifton Rd, Atlanta, GA 30322, USA; Corresponding author.
Benjamin A. Lopman
Department of Epidemiology, Rollins School of Public Health, Emory University, 1518 Clifton Rd, Atlanta, GA 30322, USA
Aron J. Hall
Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA 30333, USA
Anita K. Kambhampati
Division of Viral Diseases, National Center for Immunization and Respiratory Diseases, Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA 30333, USA
Lynn Roberts
Division of Public Health, Wisconsin Department of Health Services, 1 W Wilson St, Madison, WI 53703, USA
Jordan Mason
Division of Public Health, Wisconsin Department of Health Services, 1 W Wilson St, Madison, WI 53703, USA
Kelley Vilen
Foodborne Disease Unit, Minnesota Department of Health, 625 Robert St N, St Paul, MN 55164, USA
Ellen Salehi
Bureau of Infectious Diseases, Ohio Department of Health, 246 N High St, Columbus, OH 43215, USA
Angela Fraser
Department of Food, Nutrition and Packaging Science, Clemson University, 105 Sikes Hall, Clemson, SC 29634, USA
Carly Adams
Department of Epidemiology, Rollins School of Public Health, Emory University, 1518 Clifton Rd, Atlanta, GA 30322, USA
Norovirus is the most common cause of gastroenteritis outbreaks in long-term care facilities (LTCFs) in the United States, causing a high burden of disease in both residents and staff. Understanding how case symptoms and characteristics contribute to norovirus transmission can lead to more informed outbreak control measures in LTCFs. We examined line lists for 107 norovirus outbreaks that took place in LTCFs in five U.S. states from 2015 to 2019. We estimated the individual effective reproduction number, Ri, to quantify individual case infectiousness and examined the contribution of vomiting, diarrhea, and being a resident (vs. staff) to case infectiousness. The associations between case characteristics and Ri were estimated using a multivariable, log-linear mixed model with inverse variance weighting. We found that cases with vomiting infected 1.28 (95 % CI: 1.11, 1.48) times the number of secondary cases compared to cases without vomiting, and LTCF residents infected 1.31 (95 % CI: 1.15, 1.50) times the number of secondary cases compared to staff. There was no difference in infectiousness between cases with and without diarrhea (1.07; 95 % CI: 0.90, 1.29). This suggests that vomiting, particularly by LTCF residents, was a primary driver of norovirus transmission. These results support control measures that limit exposure to vomitus during norovirus outbreaks in LTCFs.
