Indirect immunofluorescence for the diagnosis of Lassa fever infection.

The indirect immunofluorescent technique is a rapid method for identification of Lassa virus and Lassa virus antibody. In the study reported here, Lassa virus antigen was detected by this method in Vero cell cultures within 24 hours of their inoculation with an infected human blood specimen. A diagnosis could be made from field-collected specimens within 3 days of their receipt.Fluorescent antibodies against Lassa virus were detected in human serum as early as 7 to 10 days after onset of illness, and were detected as long as 61 months after infection. Complement fixing antibodies were not as long lasting.No antigenic differences were noted by the indirect immunofluorescence technique between several Lassa virus strains isolated from Nigeria, Liberia, and Sierra Leone over a 6-year period.