Epidemic characteristics of Norovirus infection in schools in Hefei City from 2018 to 2022
Objective To understand the epidemic characteristics of Norovirus infection in schools in Hefei City,and provide scientific basis for the prevention and control of Norovirus infection in schools.Methods The investiga-tion reports of Norovirus infection reported by the centers for disease control and prevention(CDC)of all counties(cities and districts)in Hefei City and the laboratory test results of Hefei CDC from 2018 to 2022 were analyzed by descriptive epidemiological methods.The related indicators of Norovirus infection,including the attack rate,timeli-ness of reporting,duration of epidemic,clinical symptoms,as well as GⅠ and G Ⅱ classification of Norovirus were compared.Results From 2018 to 2022,there were 217 school Norovirus infections outbreaks in Hefei City,with 3 002 cases and 314 006 affected people.The average annual attack rate ranged from 0.82％to 1.32％.Most cases were from kindergartens,there were 116 cases,accounting for 53.46％,with an average attack rate of 2.87％.The time distribution was bimodal,concentrated in March-June and September-December each year.The attack rate and duration of outbreaks were both significantly higher than those of clustering epidemics(both P＜0.001).Positive correlation existed between the timeliness of reporting and the number of outbreaks at the time of receiving the re-port as well as the duration of the epidemic(r=0.182,0.783,respectively,both P＜0.001).With the advance-ment of the academic stage,the symptom with diarrhea showed an increasing trend(x2trend=743.236,P＜0.001),the symptom with vomiting presented a decreasing trend(x2trend=386.888,P＜0.001),and the symptoms with both diarrhea and vomiting presented an increasing trend(x2trend=327.264,P＜0.001),while the symptom with fe-ver presented a decreasing trend(x2trend=15.717,P＜0.001).The positive detection rate of anal swab specimens(60.10％)was higher than that of vomit and environmental specimens(38.71％,14.29％,respectively,x2=135.685,P＜0.001).The laboratory identified 181 cases with Norovirus GⅠ and G Ⅱ subtypes,including 28 cases of G Ⅰsubtype,accounting for 15.47％,and 149 cases of G Ⅱ subtype,accounting for 82.32％.Conclusion Schools are locations with high incidence of Norovirus infection.At the beginning of the school season,various prevention and control measures should be strictly implemented to improve the monitoring sensitivity of symptoms like vomiting,diarrhea,and so on,so as to achieve early detection,early report and early treatment.
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