CD40LG and hemorrhagic fever with renal syndrome: A four-fold increase in WENV IgG antibody titer and/or seroconversion was found in seven patients (Table 2), six of whom were confirmed to be HFRS cases by positive IgM detection or elevated hantavirus IgG antibody titers, while a titer of more than 1,600 of antibody against WENV in ELISA was found in three convalescent sera, suggesting a strong humoral immune response against WENV.