Influenza infection leaves otherwise healthy people open to bacterial infections, which account for a significant number of mortalities during flu season, recent research confirms.

Researchers at the Torrey Pines Institute for Molecular Studies, San Diego, CA, found that there is a heightened period of susceptibility to otherwise non-lethal bacterial infections immediately after influenza infection that increases the lethality of both pathogens. Following a flu outbreak, the most common bacterial infections include Streptococcus pneumoniae, Haemophilus influenzae, Group A Streptococcus, and Staphylococcus aureus, according to researchers.

When influenza is followed by H. influenzae infection, there is a definite restricted period of increased susceptibility, and it is the bacterial infection, not the viral infection, that contributes most to the increased lethality. The full study is scheduled to appear in the February issue of the American Journal of Pathology.