Molecular Epidemiology Study Of Pediatric Norovirus Gastroenteritis In Chongqing,2017-2019

Objective: To investigate the clinical characteristics and norovirus genotyping among children with norovirus-associated gastroenteritis,in Chongqing from 2017 to 2019,and provide epidemiological data for prevention and control of norovirus-associated gastroenteritis.Methods: A total of 1,458 stool specimens were collected from the children with acute gastroenteritis possibly caused by viral infection in Chongqing between January 2017 and December 2019,and the corresponding clinical data were recorded.Appropriate statistical methods were adopted to analyze the clinical data.The VP1 region was amplified and sequenced,and a phylogenetic tree of this region was constructed.Results: Norovirus was found in 10.8%(158/1458)of the 1,458 specimens.NoV positive rate was 10.0%(48/482)in 2017,12.3%(60/489)in 2018,and 10.3%(50/487)in 2019.It isn’t statistically significant(χ2=1.588,P>0.05).Sequence of the VP1 region showed that62.7%(99/158)of the 158 norovirus-positive specimens had GII.4 Sydney＿2012 genotype,15.2%(24/158)had GII.3,while GI.2(1/158),GI.3(2/158)and GI.5(1/158)were occasionally detected.NoV detection rate was 12.2%(105/860)in young males,while 8.9%(53/598)in females.NoV detection rate between the two genders had a statistically significant(χ2=4.088,P<0.05).91.8%(145/158)of the pediatric patients with NoV gastroenteritis in the age of onset were younger than 2 years old.The highest norovirus detection rate was in 13-18 months old group,followed by 6-12 months old group.August,September and October were the epidemic peak season,but there were some differences in peak season each year.92.4%(146/158)of the norovirus-positive samples were watery stools,while 6.3%(10/158)showed thin stools,and 1.3%(2/158)were mucous stools.The rates of vomiting,fever and respiratory symptoms were respectively 79.1%(125/158),29.1%(46/158)and 41.8%(66/158),while abdominal pain,mental wilt and rash were occasional among the accompanying symptoms.White blood cells in stool samples were detected in 28 cases,red blood cells were detected in 4 cases.Co-infections with NoV and rotavirus were found in 23 cases.Conclusions: Norovirus-associated gastroenteritis was commonly seen in children less than 2 years and reached the epidemic peak in August,September and October.There was a significant difference in detection rate between the two genders.GII.4 Sydney＿2012 and GII.3 were the predominant strains in Chongqing between 2017 and 2019,while the GI showed an occasional phenomenon.Some children were found to have co-infections with rotavirus.