Waterborne Outbreak of Acute Gastroenteritis Caused by Recombinant Norovirus GII.P7–GII.6 in Khabarovsk in 2019

Background: Noroviruses are common causative agents of acute gastroenteritis worldwide. Person-to-person transmission is the dominant transmission route for norovirus infection but contaminated water also often leads to outbreaks. Objectives: Our purpose was to do epidemiologic and molecular genetic analyses of waterborne norovirus infection outbreak among children in Khabarovsk in 2019. Materials and methods: Clinical and water samples were screened for the presence of norovirus RNA using real-time RT-PCR detection kit. The norovirus nucleotide sequences were determined by Sanger sequencing. The obtained sequences were subjected to a phylogenetic analysis. Results: In July 2019, 34 children developed acute gastroenteritis in Khabarovsk. The epidemiologic investigation showed that on the eve of the disease onset all patients played and bathed in a pedestrian fountain complex. A molecular genetic analysis of 18 biological samples from children with acute gastroenteritis and a water sample from the fountain revealed a recombinant norovirus GII.P7-GII.6. We established a 100.0% identity of all obtained nucleotide sequences to each other. A phylogenetic analysis of ORF2 partial sequences showed that the capsid protein of the Khabarovsk GII.P7-GII.6 strains belonged to the variant GII.6a. Conclusions: Contaminated water in the pedestrian interactive fountain complex was the most likely cause of the norovirus infection outbreak among children in Khabarovsk in 2019 associated with the lack of proper maintenance and regular disinfection measures.