Rapid death in children by type B influenza virus associated with neurological complications

Background: During the 1994–1995 season, an increase in the circulation of influenza type B was observed in our infantile population, according to serological studies (hemagglutination-inhibition). We reported the case of four children (<1 year old) that were diagnosed with influenza-like illness, who developed a severe disease (rapid progressive encephalopathy) with high fever, drowsiness and recurrent convulsions, and were presumptively diagnosed with encephalomyocarditis. Brain and lung necropsies were carried out. Materials and methods: Initial laboratory diagnosis was done by immunofluorescence assay on brain and lung samples, followed by viral isolation in MDCK cells and chicken eggs. The isolates were characterized antigenically by haemagglutination-inhibition assay (HI) with post-infection ferret antisera. Results: For the immunofluorescence technique, four samples were positive. In MDCK and chicken eggs, six haemagglutinating agents characterized by hemagglutination-inhibition were similar to the B/Beijing/184/93-like reference strain (four from the lungs and two from the brain). Data from the morbidity report will be presented. Serological studies (monosera and pair sera) showed an increase in the circulation of influenza B in our infantile population. Conclusions: The pathogenesis of encephalopathy is still not clarified. However, we believe that viremia is the key to initiation. There is an urgent need to promote vaccination against influenza in young children to prevent these devastating disease conditions.