Epidemiological Characteristics Of And Meteorological Effect On Influenza Viruses By Subtypes And Lineages In Jiangsu Province

Objective: Worldwide,annual influenza epidemics are estimated to result in beyond 3 million severe cases,and beyond 290 thousand respiratory deaths.It is difficult to accurately predict the timing and intensity of seasonal influenza epidemics.The difference in epidemiological characteristics between influenza viruses of different subtypes and lineages have not been elucidated.This study aimed to fill this gap using surveillance data from Jiangsu province from2015 to 2019.We also explored the impact of meteorology on influenza viruses by subtypes and lineages,informing the precise prevention and control of influenza.Methods: All the laboratory-confirmed influenza cases from the Influenza Surveillance Network of Jiangsu Province during January 2015 and December 2019 were included in this study.We used seasonal decomposition method to describe the seasonality of influenza viruses by subtypes and lineages,and used χ2 test,logistic regression to investigate the infection risk of subpopulation with different subtypes and lineages.We also collected daily meteorological data,including temperature,relative humidity,and barometric pressure,from an open-access data sharing platform,during the research period,whereby,analyzed the impacts of meteorological factors on the activity of influenza viruses by subtypes and lineages,using poisson distribution-based Distributed Lag Non-linear Model(DLNM).Results: 1.A total of 18,720 laboratory-confirmed influenza cases were reported via surveillance in Jiangsu Province from 2015 to 2019.Among them,cases positive for influenza A(H3)virus accounted for the most(34.96%),followed by A(H1)subtype(26.44%).B-V and B-Y lineages accounted for 22.75% and 15.63% respectively.The seasonal increase of influenza activity was commonly observed in winters,and also was seen in summers during our research period.2.The seasonal activity of influenza A(H1)and B viruses increased in winters only.The activity of A(H1)and B-Y viruses could peak as early as in December,and remain elevated till next February.The activity of B-V virus peaked later,usually during January and February.In contrast,the increased activity of A(H3)virus could occur both in winters(January to February)and summers(August to September).3.Children younger than 5 years old in A(H1)virus cases were higher risk of infection,and teenagers aged 6 ～ 15 in B-V cases were higher.A(H3)and B-Y cases had greater detection possibilities in individuals aged 16 ～ 25 and over 65 year olds,respectively.4.The effects of daily average temperature,relative humidity and barometric pressure on influenza activity were in non-linear and lagged manner,and varied by influenza subtypes and lineages.The risk of increased incidence was higher for all influenza viruses at low daily average temperatures,whereas was only for A(H3)virus at high temperatures(lag 0,10 day).At low daily average relative humidity,the relative risk(RR)became higher for A(H1)and B viruses(lag 0,4～5 day).When the daily average relative humidity was high,the increase of RR was more evident for influenza A virus(lag 4,5 day).As for high daily average barometric pressure,an increased RR was observed for influenza A and B-Y viruses.During days with low barometric pressure,the RR was elevated for A(H3)and B-V viruses(lag 1 day).Different meteorological factors presented different combinations of immediate,short-term and long-term effects on influenza incidence by subtypes and lineages.Conclusions: 1.Influenza viruses had subtype and lineage specific epidemiological characteristics.A cross-type similarity in seasonality was observed between A(H1)and B-Y viruses: both had high-risk trends in winner.A(H3)virus had unique bimodal trends in winner and summer,which was main popular virus subtype.Targeted measures should be taken according different characteristics of the virus types.2.The effects of daily average temperature,relative humidity and barometric pressure on influenza activity were non-linear and lagged.Low temperature(< 0℃),low relative humidity(<40 %)and high barometric pressure(1022 ～ 1026 h Pa)could increase the risk of influenza pandemic.The cumulative and lagged distribution effects of meteorological factors varied by influenza subtypes and lineages.It is recommended that relevant departments should strengthen publicity and education,and take prevent and control measures positively.