An outbreak of norovirus diarrhea in a welfare home for the elderly in Shanghai

ObjectiveTo investigate an outbreak of norovirus diarrhea in a welfare home for the elderly in Shanghai， and to analyze the epidemiology and virus genotype characteristics of the epidemic， thus providing a scientific basis for the prevention and control of norovirus epidemic.MethodsCase definition was clarified. After case definition， a standardized questionnaire was used to carry out case investigation to make comprehensive analysis in combination with field epidemiological investigation and laboratory tests results.ResultsThe epidemic lasted for 14 days， and 23 cases were reported with an incidence rate of 12.37% （23/186）， including 3 males and 20 females. There were more cases on the 1st， 4th and 6th floor of the main building in the welfare home， accounting for 52.17% （12/23） of total cases. 19 cases were reported in the main building， with an incidence rate of 11.59% （19/164）； 4 cases were reported in the auxiliary building， with an incidence rate of 18.18% （4/22）. There was no significant difference in the morbidity between the main building and the auxiliary building （χ2=0.779，P>0.05）. The main clinical manifestations were vomiting and diarrhea. There was a significant difference in the incidence of vomiting symptoms among the elderly， nursing staff and other staff in the welfare home （χ2=10.216， P0.05）. Fecal samples were collected from 23 cases， 1 case family member， 68 risk personnel and 14 environmental surface swab samples. Norovirus GⅡ was detected in stool samples of 19 cases， 1 family member and 36 risk personnel.ConclusionOutbreak of norovirus infection is reported in a welfare home in Shanghai. The close contact between the elderly and health workers might lead to the outbreak.