Epidemiological and Whole-Genome Sequencing Analysis of a Gastroenteritis Outbreak Caused by a New Emerging Serotype of in China.

is an important foodborne pathogen with diverse serotypes. In May 2021, we investigated a gastroenteritis outbreak that occurred in China, caused by O10:K4 infection. Based on the epidemiological curve, this outbreak was identified as a homologous exposure event. A case-control study demonstrated that emperor crab with mashed garlic (odds ratio [OR] = 4.60,  = 0.030; 95% confidence interval [95% CI]: 1.11-19.14), goose liver geoduck (OR = 4.50,  = 0.029; 95% CI: 1.12-18.13), shrimp (OR = 4.89,  = 0.021; 95% CI: 1.22-19.65), and sea cucumber (OR = 7.36,  = 0.005; 95% CI: 1.68-32.26) were the potential sources of the food poisoning. isolates from 18 laboratory-confirmed cases were all serotyped O10:K4, and determined to be sequence type ST3 via multilocus sequence typing. Pulsed field gel electrophoresis and whole-genome sequencing analysis revealed the identical pattern and 0-2 single nucleotide variation among these isolates. was positive in all isolates, while and Orf8 were absent. Seven essential base positions in for pandemic clone identification were identical between the O10:K4 and O3:K6 pandemic clones. Phylogenetic analysis with 45 additional genomes of 13 different serotypes showed the closest genetic relationship between O10:K4 and O1: KUT. O10:K4 was thought to evolve from the O3:K6 pandemic clone. The new serovariant of O3:K6 poses a challenge for the prevention and control of disease outbreaks, or even epidemics, in the future.