Analysis a family outbreak of epidemic hemorrhagic fever in Yingkou City of Liaoning Province

Abstract

Objective To investigate and analyze the epidemiological characteristics of epidemic hemorrhagic fever (EHF), and explore the causes and possible routes of transmission in Yingkou City for proposing prevention and control measures. Methods A case restropective investigation was done to all outbreak cases of EHF in Yingkou City, relevant epidemiological investigation, clinical examination and laboratory test were done. Search of case and new case were carried out in the population. Density of rats (night clip) and rate of rat infection (Hanta virus antigenemia) in the region of the epidemic area of EHF were investigated. Blood samples were collected, antibody of EHF was detected with enzyme linked immunosorbent assay (ELISA). The rat lung was detected virus antigen using immunofluorescence. EHF diagnosis was based on Diagnostic Criteria for Epidemic Hemorrhagic Fever (WS 278-2008). Results The results of the case study showed that a family of three was infected with the same disease in one month. It was a family cluster of EHF. Of the three cases, one case was Seoul virus (SEO) positive and showed infection for rattus type. Totally 54 human serum samples from the case search in key groups were tested. Two cases were seropositive with IgG, through epidemiological investigation, all people were healthy. On physical examination they had no symptoms such as viral infection with fever, fatigue, symptoms of three red and pains of EHF. Two cases were determined latent infection. The patient's living and health conditions were very poor. The floor of indoor was soil, all of the things were placed in chaos in this family, there were many signs of rats and rat holes in the yard, and there were several rat holes around the wellhead. Rat density surveillance showed that cloth clip 108 times, effective clamp 105 times, 4 rats were captured, and the density of rats was 3.81%. The density of rats exceeded the national standard of no more than 1% of the residential area. All the rats were Rattus norvegicus. Detection of lung antigen was negative in rats by immunofluorescence. Conclusions This event is a family cluster of EHF caused by Rattus norvegicus. Rodent prevention and control, improving family conditions and environmental management are essential measures for blocking of the disease transmission and infection controlling. Key words: Epidemic hemorrhagic fever; Family cluster; Epidemiological investigation