Studies On Significant Epidemiological Characteristics Of Severe Fever With Thrombocytopenia Syndrome And Coronavirus Disease 2019 In China’s Mainland

Background New infectious diseases are emerging one after another and seriously endangering human health.Severe fever with thrombocytopenia syndrome(SFTS)is an emerging infectious disease which was first found in China in 2009.The epidemic area continues to expand and the number of cases increases year by year.SFTS was listed as one of 10 priority diseases in the Research and Development Blueprint by the World Health Organization.Coronavirus disease 2019(COVID-19)has been a global pandemic,which has been seriously endangering human life and health since the end of 2019.The purpose of this study was to do the systematic epidemiological analysis of SFTS and,at the same time,starting the research of COVID-19 right away in order to understand the spatiotemporal transmission dynamics,epidemic season,environmental factors and gender differences of these two seriously emerging infectious diseases.Based on the results,it can determine the high-risk regions,high infection seasons and high-risk groups and provide scientific basis for targeted prevention and control measures.Methods We collected data of 2010-2018 years of SFTS cases and the cases of COVID-19 as of February 27,2020 from the China Information System for Diseases Control and Prevention(CISDCP).Information of each case in the surveillance system included demographic characteristics(age,gender and residence location),date of illness onset,date of diagnosis and date of death(if applicable).Demographic data came from China’s sixth census in 2010;meteorological data came from China’s meteorological data sharing service system,collecting meteorological data of major research sites from 2010 to 2018,including daily average temperature,midity(1%),daily sunshine duration.We used the national surveillance database of the diseases in China’s mainland to compare gender differences in incidence or attack rate(AR),proportion of severe and critical cases(PSCC)and case fatality rate(CFR)in relation to age,affected province and onset-to-diagnosis interval.Multiple logistic regression analysis was used to explore the risk factors related to the severity and death of SFTS and COVID-19 and to verify the sex difference of mortality and PSCC.The sex difference in case fatality rate was validated by multivariate logistic regression analysis using SPSS software(version 24.0).We created thematic maps displaying spatial distribution of AAIR and CFR by geographic information system(GIS)technology in ArcGIS 9.2 software(ESRI Inc.,Redlands,CA,USA).A heat map was created to quantify the seasonal pattern of SFTS in each region,and time series sequences were drawn by using R.Pearson correlation coefficient between monthly incidence and meteorological factors was calculated.ResultsFrom 2010 to 2018,a total of 15234 patients with SFTS were reported.The incidence rate increased from 0.08 per million persons in 2010 to 2.21 per million persons in 2016 and the average annual incidence rate during the nine years was 1.27 per million persons.The CFR was the highest in 2010(14.02%)and then decreased year by year to 2.51%in 2016,then increased slightly in the next two years.The overall nine-year mortality rate was 4.48%.The annual average morbidity and mortality of SFTS were age-dependent and increasing with age.In terms of the spatial distribution of diseases,the SFTS area in China had expanded from 30 counties in 7 provinces in 2010 to 253 counties in 20 provinces in 2018.99%of the cases were concentrated in 7 provices,including Shandong and Henan.The annual average morbidity and mortality rates varied greatly.The spatial distribution of SFTS continued to expand and mainly concentrated in Shandong province,Henan province and other seven regions with significant regional differences.There was a certain seasonal pattern in the distribution of SFTS.More than 96%of cases occurred from April to October each year,and the peak disease time of different latitude groups were slightly different.The incidence peak period of 40-45 latitude was later,the disease distribution period was shorter,the incidence peak period of 30-35 latitude was earlier and the disease distribution period was longer.There were differences of SFTS between male and female.The average annual incidence rate of female was 1.40 per million persons,significantly higher than male(1:15 per million),RR=1.21.However,the CFR of women was lower than that of male(3.85%vs.5.20%,OR=0.74).Meanwhile,there was a certain age-dependent gender differences.The incidence of females in the 40-69 year old group was significantly lower than that in men.and the CFR in all age groups was lower than in female.After adjusting for potential confounding factors,the female-to-male difference in AAIR and CFR remained significant in multivariate analysis.As of February 27.2020,78832 cases of COVID-19 were collected in China’s mainland.The AR,PSCC and CFR were all age-dependent.The AR and CFR increased with age.The AR was significantly higher in female population than in male population with a RR of 1.06.By contrast,PSCC and CFR were significantly lower among female patients,with an OR of 0.84 and 0.55 respectively.The AR,PSCC and CFR varied greatly from province to province.After adjusting for age,affected province and onset-to-diagnosis interval,the female-to-male difference in AR,PSCC and CFR remained significant in multivariate analysis.Conclusion The distribution of the disease population and spatial distribution of the epidemiological characteristics of SFTS were respectively different;the period of peak and epidemic in different latitudes were not similar.Geography and climate are important factors affecting the spatial distribution of diseases.The peak time and epidemic period of SFTS are different in different latitudes.The incidence and fatality of SFTS and COVID-19 were increasing with age,but female patients had lower fatality than male patients in all age groups.We elucidated an age-dependent gender dimorphism for SFTS and COVID-19 respectively,in which the female individuals had higher susceptibility but lower severity and fatality.The finding of the above new epidemiological characteristics provides an important scientific basis for the effective control of the two diseases.The characteristics of the gender differences in the occurrence and outcome of the diseases expand the cognition of the transmission routes and pathogenesis of the new infectious diseases,and provide an important clue and exploration space for the research of drug targets.