Molecular characteristics of norovirus in acute gastrointestinal illness, Tianjin, 2019

ObjectiveTo analyze the genetic characteristics of norovirus in acute gastrointestinal illness population in Tianjin in 2019.

MethodsStool samples from acute gastroenteritis patients in outbreaks and clusters of the disease or sporadic cases collected by all 16 district CDCs in Tianjin were detected with RT-PCR. The polymerase and capsid genes of the isolated strains were amplified. Phylogenetic tree was constructed for sequences analysis.

ResultsA total of 1615 samples were detected by district-level CDCs, in which 97 were positive for norovirus (6.01%). The positive samples were detected all the year around except January. The positive rate was 1.11% for norovirus GⅠ and 5.02% for norovirus GⅡ respectively. The result of genotyping of both polymerase and capsid was as follow: GⅡ.2［P16］, GⅡ.4［P31］, GⅡ.17［P17］, GⅠ.3［P13］, GⅡ.6［P7］, GⅠ.5［P4］, GⅡ.3［P12］, GⅠ.5［P12］, GⅠ.1［P1］ and GⅠ.2［P2］. The top three genetic recombination strains of norovirus detected in 13 cases of acute gastroenteritis in outbreaks and clusters of the disease were GⅡ.2［P16］ (30.77%, 4/13), GⅡ.4［P31］ (23.08%, 3/13) and GⅡ.17［P17］ (23.08%, 3/13).

ConclusionThe genotypes of norovirus was diverse in Tianjin. The coevolution and circulation of different genotypes continue, so it is necessary to further strengthen the surveillance and molecular typing of norovirus.