The Analysis Of Current Situation Of Epidemic Foci And Epidemiological Characteristics Of Hemorrhagic Fever With Renal Syndrome In Shandong Province

Hemorrhagic fever with renal syndrome(HFRS)is a global natural epidemic disease caused by Hantavirus(HV).It is widely distributed in the world,and the high-incidence area is mainly concentrated in Eurasia.Its clinical symptoms are characterized by fever,hemorrhage and kidney damage.China is the most severely affected country in the world.The annual average incidence rate is about 3.5/100,000,and the reported number of HFRS cases accounts for more than 90%of the world.The northeastern,eastern,central and southwestern China is the high-risk areas of HFRS.Hantaviruses,members of the genus Hantavirus and order Bunyavirales,are enveloped,single-stranded,and negative-sense RNA viruses.The virus genome consists of three separate segments,referred to as the small(S),medium(M),and large(L)segments.In China,the subtypes of HV can cause HFRS are mainly SEOV and HTNV,and different HV have single host.The hosts of SEOV are Rattus norvegicus and Mus musculus,and the hosts of HTNV are Apodemus agrarius and A.peninsulae.Since the first case of HFRS found in Shandong Province in 1962,the epidemic of HFRS has experienced several fluctuations,it has became a serious threat to human health.However,under the influence of various factors,the HFRS foci have changed in different periods.The HFRS foci with different characteristics have shown different influence on population’s health,and lead to new challenges to the prevention and control department.In the past decade,the HFRS epidemic situation in Shandong Province still has periodical change.It has important public health significance to figure out the changes and current situation of HFRS foci,for helping to take measures to prevent HFRS in key areas.The objectives of this study were to investigate the epidemiological characteristics of HFRS,illuminate the current epidemic hotspots and analyze the process of changes of HFRS foci in Shandong Province in recent years.Materials and Methods:This study combines traditional epidemiology with molecular epidemiology and surveillance of HV host.Based on the data of HFRS in Shandong Province from 2005 to 2016,the epidemiological characteristics of HFRS were analyzed.The HV host monitoring data of 4 fixed monitoring points and 14 temporary monitoring points were used to discuss the characteristics of HV vectors.Phylogenetic analysis was employed to identify the distribution of HV and their relationship with strains isolated in other regions.We integrated the above results and existing research results,discussed the migration of HFRS foci in Shandong Province from 2005 to 2016 comprehensively,showed the characteristics of HFRS foci at the present stage,and provided corresponding reference for further prevention and control measures for HFRS.Results:1.A total of 15998 cases and 199 deaths of HFRS were reported in Shandong Province from 2005 to 2016,with an annual incidence rates(per 100,000)ranged from 0.97 to 2.62,and the mortality rates ranged from 0.78%to 2.29%.It still has a bimodal seasonal cycle dominated by autumn and winter peaks.The high-incidence area was mainly concentrated in central and southeastern Shandong,showing a distribution characteristic that the number of cases in southeastern Shandong was over than that of northwestern Shandong.The most case number was in the 41-50 age group,which accounted for 26.15%.The sex ratio(male/female)was 2.61,and the largest occupational group was peasant,which accounted for 82.12%.2.During the study period,893738 mouse traps were placed at fixed monitoring sites,and 10538 animals were captured,including Rattus norvegicus,Mus musculus and Apodemus agrarius and so on,with an average rat density of 1.18%,10384 samples were sent for examination and 241 were positive for test,the average virus carriage rate was 2.32%.A total of 1798 animals were captured in temporary monitoring sites.All of them were sent for test,and 111 were positive for test,the average virus carriage rate was 6.17%.3.A total of 1798 samples captured in 14 temporary monitoring sites were sent to test,and 111 were positive for detection,including 19 HTNV,90 SEOV,and 2 other types of HV.Phylogenetic analysis of L,M,and S segments showed that the HV strains obtained in this study were generally distributed in the same branch,and had close genetic relationship with strains isolated in Beijing,Zhejiang,Fujian,Shaanxi,South Korea,and North Korea.However,two strains were found different from other strains but close to the strains isolated in northeastern China and the Russian Far East(Jewish Autonomous Prefecture,Khabarovsk).4.According to time and the characteristics of HFRS in Shandong Province,we divided the whole research into two phases:phase 1 is from 2005 to 2010,and phase 2 is from 2011 to 2016.The HFRS foci of Shandong Province in phase 1 were divided into two epidemic foci,which were a and b.And the HFRS foci in phase 2 were divided into three epidemic foci,which were c,d and e.The epidemic foci a is located in central Shandong,dominated by Rattus norvegicus and Mus musculus,belongs to Rattus type focus,with a bimodal seasonal cycle dominated by spring peaks.The disease-causing HV is generally SEOV.The epidemic foci b is located in southeastern Shandong,dominated by Rattus norvegicus,Mus musculus and Apodemus agrarius,belongs to mixed-type focus dominated by Rattus norvegicus,with a bimodal seasonal cycle dominated by autumn-winter peaks.The disease-causing HV include SEOV and HTNV.The epidemic foci c is actually the new status of epidemic foci a,which dominated by Rattus norvegicus and Mus musculus,belongs to Rattus type focus.But the proportion of Apodemus agrarius in where near southeastern Shandong has increased.It has a bimodal seasonal cycle dominated by autumn-winter peaks.The disease-causing HV is mainly SEOV.The epidemic foci d is actually the new status of epidemic foci b,which dominated by Apodemus agrarius,belongs to mixed-type focus dominated by Apodemus agrarius.It has a bimodal seasonal cycle dominated by autumn-winter peaks.The disease-causing HV include SEOV and HTNV.The epidemic foci e is located in southwestern Shandong dominated by Rattus norvegicus and Mus musculus,belongs to Rattus type focus.The disease-causing HV is SEOV,with a bimodal seasonal cycle dominated by spring peaks.Conclusion:1.The epidemic of HFRS in Shandong Province has kept changing for many years.It is currently in a state of sporadic and at a historically low level.However,it is necessary to strengthen prevention and control measures at any time because of its periodic changes.2.The disease-causing HV in Shandong Province are still SEOV and HTNV,and the dominant host species are still Rattus norvegicus and Apodemus agrarius.It deserves our vigilance that two strains we found are different from others.The follow-up surveillance is necessary to perform to determine the pervasiveness and harmfulness of the phenomenon that HV can spill over to their non-fixed hosts.3.The HFRS epidemic foci in central Shandong start to incline to southeastern Shandong.The peaks of HFRS incidence is more inclined to the autumn-winter peaks.The change of host population in the intersection of this two areas is active and it may become high-risk area in future.The prevention and control department should pay more attention in this region.