Surveillance of hemorrhagic fever with renal syndrome in Ganyu County from 1995 to 2005

Objective The study was conducted to analyze the surveillance results of the epidemic of hemorrhagic fever with renal syndrome (HFRS) among rats and crowds and the control effect of HFRS,and to explore the effective way of HFRS controlling. Methods The disease surveillance data,information and population data from the Center for Disease Control and Prevention of Ganyu County were retrospectively analyzed. Results The number of HFRS cases was 923 with 9 deaths in the last 11 years,the annual incidence being 8.06/lakh; the fatality rate was 0.98%. Cases occurred in each month all the year round,presenting with the spring peak with a declining trend and the autumn and winter peak with an ascending trend. Cases of HFRS were distributed in all 18 towns,more cases in the hilly lands than in the plain area and thus than in the coastal area. The incidence in hilly and plain area was declining. The cases distributed mainly in the 30-50 age group,accounting for 67.28%. The sex ratio was 2.25∶1,showing a declined trend. 87.97% of the cases occurred among farmers,and 6.18% among the students. The immunological study in the last 11 years indicated that the average anti-HV lgG positive rate among health people was 11.37%,the sub-clinical infection rate being negative correlated with the epidemic among people. The coincidence of the serum test among clinical diagnosed patients was 64.39%,indicating considerable misdiagnoses. The density and carrier rate of host rats indoor in spring and outdoor in autumn and winter were investigated each year since 1995. The captured rats were divided into 6 species in 3 families of 2 orders. Among them,the predominant species of the rats were R.rattus indoor and A.arariue outdoor,the virus carrier rate being 2.76% and 3.06%,respectively; the virus carrier index was 0.028 in spring and 0.025 in autumn and winter. The carrier index in spring was positively correlated with the annual incidence and incidences of the spring peak and the autumn and winter peak; the index in autumn of outdoor rats (1995-2004) was positively correlated with the spring peak of HFRS incidence next year (1996-2005),according to the correlation analysis between the surveillance data and epidemic since 1995 in the county. Conclusion Vaccine inoculation is an effective way to control HFRS.