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

Carly Adams; David Young; Paul A Gastañaduy; Prabasaj Paul; Zach Marsh; Aron J Hall; Benjamin A Lopman

The copyright holder for this preprint (which was not peer-reviewed) is the author/funder. . https://doi.org/10.1101/707356 doi: bioRxiv preprint 216 (54%). Of the 9 cases excluded from regression analyses for having R Ei = 0, 55% were residents, 217 55% reported vomiting, and 55% reported diarrhea. All six outbreaks were caused by norovirus 218 genogroup II, two of which were confirmed as GII.4 Sydney and four of which were not 219 genotyped. Outbreaks began with one to three index case(s) (nine index cases in total), defined as 229 cases with onset of symptoms on day one of an outbreak, that had large estimated R Ei 's (range: 230 1.48 to 8.70) relative to other cases in the outbreak. After the index case(s), each outbreak either 231 continuously declined to a R Ei below 1 or increased again before declining to a R Ei below 1 (Fig 232 1 ). Of these index cases, at least one from each outbreak reported vomiting (Fig 2) . While most 233 index cases also reported diarrhea, outbreak 6 began with a case that reported vomiting only. This article is a US Government work. It is not subject to copyright under 17 USC 105 and is also made available for use under a CC0 license.