In our study, IFA was adopted to detect the epidemic haemorrhagic fever virus (EHFV) antigen and antibody. We studied on the mode of transmission of EHFV in mice and its epidemiologic significance. The results demonstrated that both horizontal and vertical modes of transmission existed in mice under natural circumstances. Horizontal transmission was noticed as the major mode of transmission of EHFV in mice which played an important role in the spread and development of EHF natural foci. Vertical transmission seemed to act merely on the maintenance of EHF natural foci in mice.