The use of transportable single-radial-diffusion immunoplates in seroepidemiological studies of influenza in the Gambia. The occurrence and persistence of antibody to influenza A/Hong Kong/68 (H3N2) virus in selected inhabitants of two rural villages.

Seroepidemiological studies of influenza in the Gambia were made using transportable single-radial-diffusion immunoplates containing A/Hong Kong/68 (H3N2) virus as antigen. The frequency and durability of antibody so detected in selected residents of two Gambian villages (Manduar and Kafuta) are described. Transportable immunoplates were found to be an effective method for the serological surveillance of influenza and to be applicable in studies in remote areas where laboratory facilities may not be available. Results indicated that infection with influenza was widespread in Manduar residents on several occasions between 1968 and 1974 and that reinfection with A/Hong Kong/68 virus or its antigenic variants occurred frequently. Serum levels of antibodies to the haemagglutinin and neuraminidase antigens of the A/Hong Kong/68 virus often persisted for only a short time (mean half-life about 28 days), particularly after first infections. Antibody persistence increased following repeated reinfection. No precise explanation can be offered at present for the relatively short persistence of antibodies in Gambians. Possible reasons include genetic and environmental factors, depressed immunological reactivity associated with concurrent infection (notably parasitic diseases), and unusually high rates of synthesis and catabolism of immunoglobulins. The value of transportable immunoplates for serological surveys and for accurate assessment of antibody persistence is discussed.