Norovirus Outbreak Due to Person-to-person Transmission in a College in Kerala, India, 2021.

We investigated a cluster of acute gastroenteritis reported from a college in Kerala on December 1, 2021. We defined a suspect case as an occurrence of vomiting or at least three episodes of loose stools within 24 h. We identified 113 suspected case patients; 63 (55.8%) were boys, and 110 (97.3%) were hostel inmates. All five stool samples and three out of eight water samples we collected tested positive for norovirus. We conducted a retrospective cohort and did univariate and multivariable binomial regression to calculate the adjusted risk ratio (aRR). Norovirus infection risk was higher among those who had a symptomatic roommate (aRR - 4.69; 95% confidence interval [CI]: 3.05-7.22) and who drank water from the jar (aRR - 1.41; 95% CI: 1.08-1.86) and filter in boys' canteen (aRR - 1.40; 95% CI: 1.04-1.89) and filter in Boys' hostel (aRR - 2.02; 95% CI: 1.63-2.49). We recommended changing water filters and frequent handwashing with soap.