Epidemiology Of Hand,foot,and Mouth Disease And The Genetic Characteristics Of Coxsackievirus A16 In Taiyuan,shanxi,China From 2010 To 2021

Purposes:Taiyuan City established a HFMD surveillance system in 2010,but the epidemiology of HFMD and the genetic characteristics of CVA16 remain unclear,and especially require continuous surveillance and analysis.To address this problem,we investigated the epidemiology of hand,foot,and mouth disease and the genetic characteristics of Coxsackievirus A16 in Taiyuan,Shanxi,China from 2010 to 2021.Methods:1.Throat swab or stool specimens were collected from clinically diagnosed HFMD cases within three days of onset at the district and county Centers for Disease Control and Prevention(CDC)in Taiyuan City.In total,6641 specimens were collected during2010–2021 and sent to the virus microbiology laboratory in Taiyuan CDC for enterovirus nucleic acid detection.The data of HFMD cases in Taiyuan City from January 2010 to December 2021 was obtained from the China Information System for Disease Control and Prevention.Data analysis were conducted using Excel and SPSS statistical software.2.The collected samples were first extracted for enterovirus RNA;RNA samples were tested for EV typing using Enterovirus 71& Coxsackie Virus A16 & Enterovirus Real Time RT-PCR Kit.For the positive samples detected as CVA16,the VP1 region was amplified with the specific primer pair of CVA16,and the partial nucleotide sequence of the virus was obtained by nucleotide sequencing.3.The resulting sequences were spliced and aligned using Sequencher(version 5.4.6)software;nucleotide and amino acid similarity analyses were performed using Bio Edit software(version 7.2.5).The entire VP1 sequences of Taiyuan CVA16 strains were aligned with the reference strain worldwide using pairwise alignment in MEGA(version11.0.11).The construction of phylogenetic tree was used the neighbor-joining method.Results:1.From January 1,2010 to December 31,2021,the number of HFMD cases was71,158 in total reported in Taiyuan City.The annual average incidence rate of HFMD was123.69 cases per 100,000 individuals.Most HFMD cases were observed in the age group of one to five years in Taiyuan,Shanxi Province 84.42%(60075/71158).The annual average incidence in males was 144.41 per 100,000 individuals and that in females was101.20 per 100,000 individuals.Males had a significantly higher prevalence of HFMD than that in females(χ~2 =22188.249,P<0.001),with a mean male-to-female sex ratio of1.47:1.2.Except being affected by the COVID-19 epidemic in 2020,the monthly distribution of HFMD cases showed two epidemic peaks;one peak was from May to August and the other peak was from October to December.And the peak of cases showed a slight but obvious shift from June before(including)2016 to July since 2017.During the COVID-19 pandemic,an epidemic peak of HFMD was only observed from October to December in2020,which accounted for 74.33% of the annual cases.3.Etiological tests showed that enterovirus nucleic acid was detected using real-time reverse transcription polymerase chain reaction in 6641 clinical specimens collected from patients with HFMD from 2010-2021;overall,4236 EV-positive specimens were detected,including 988(23.32%)EV-A71,1488(35.13%)CVA16,and 1760(41.55%)other enteroviruses.4.Our results showed that all CVA16 strains found in Taiyuan City belonged to the B genotype,B1 subgenotype.The Taiyuan CVA16 strains in the phylogenetic tree were divided into two clades,belonging to the B1 a and B1 b evolutionary branches.Among all strains,184 were identified as subtype B1 b and 38 as B1 a.The 184 B1 b strains,were divided into two transmission chains,one prevalent in 2012-2019 and the other in2016-2021.The 38 B1 a strains were prevalent in 2010-2015 and in 2019-2021.5.Upon calculating the similarities in nucleotides and amino acids,the sequences of strains of CVA16 were found to have high similarity with each other;the nucleotide similarity was 86.5-100% and the amino acid similarity was 96.9-100%.Further,the CVA16 strains showed 74.2-77.2% and 90.9-92.2% similarity in the nucleotide and amino acid sequence with the CVA16 prototype strain(G10 strains),respectively.184 B1 b CVA16 strains shared 90.6-99.8% and 97.9-100% similarity in the nucleotide and amino acid sequence,respectively.Thirty-eight B1 a CVA16 strains shared 90.5-99.8% and97.6-100% similarity in nucleotide and amino acid sequences,respectively Conclusions:Based on the data from a twelve-year(2010-2021)surveillance of HFMD cases in Taiyuan city,the results indicate that children aged 1-5 years accounted for most outbreaks.More infections were found in males than in females.Although HFMD cases have been reported throughout the year in Taiyuan City,the monthly distribution showed two peaks in HFMD epidemics,with one peak between May and August,the other peak occurs in November.These results indicate epidemiological surveillance and prevention efforts should focus on the periods from May to August and from October to December.According to the epidemic characteristics of HFMD in Taiyuan,it is necessary to focus on high-risk areas and take preventive measures in advance before the high incidence time to reduce the prevalence of HFMD.