Haemophilus influenzae

a species once thought to be the cause of epidemic influenza. Noncapsulated strains are normal inhabitants of the human nasopharynx (biovars II and III). In children, capsulated strains of biovar I are the major cause of bacterial meningitis, and may also cause potentially fatal acute epiglottitis. In both children and immunocompromised patients it can cause pneumonia (see Haemophilus influenzae pneumonia>).