Quantifying the roles of vomiting, diarrhea, and residents vs. staff in norovirus transmission in U.S. nursing home outbreaks

by Carly Adams, David Young, Paul A. Gasta ñaduy, Prabasaj Paul, Zach Marsh, Aron J. Hall, Benjamin A. Lopman The role of individual case characteristics, such as symptoms or demographics, in norovirus transmissibility is poorly understood. Six nursing home norovirus outbreaks occurring in South Carolina, U.S. from 2014 to 2016 were examined. We aimed to quantify the contribution of symptoms and other cas e characteristics in norovirus transmission using the reproduction number (REi) as an estimate of individual case infectivity and to examine how transmission changes over the course of an outbreak. Individual estimates ofREi were calculated using a maximum likelihood procedure to infer the average number of secondary cases generated by each case. The associations between case characteristics andREi were estimated using a weighted multivariate mixed linear model. Outbreaks began with one to three index case(s) with large estimatedREi’s (range: 1.48 to 8.70) relative to subsequent cases. Of the 209 cases, 155 (75%) vomited, 164 (79%) had diarrhea, and 158 (76%) were nursing home residents (vs. staff). Cases who vomited infected 2.12 (95% CI: 1.68, 2.68) times the number of individuals as non-vomiters, cases with diarrhea infec ted 1.39 (95% CI: 1.03, 1.87) times the number of individuals as cases without diarrhea, and resident-cases infected 1.53 (95% CI: 1.15, 2.02) times the number of individuals as staff-cases. Index cases tended to be residents (vs. staff) who vomited ...
Source: PLoS Computational Biology - Category: Biology Authors: Source Type: research