(B) Haemophilus influenzae. # Meningitis: This is the most serious disease produced by H. influenzae with case fatality rates up to 90 per cent in the untreated.> Bacilli reach the meninges from the nasopharynx through the bloodstream.> Disease is more common in children between two months and three years of age.> Age incidence has been correlated with the absence of bactericidal anti-PRP antibodies.> Older children develop immunity as a result of subclinical infection.> It has been reported that in the tropics, non-type b strains may be responsible for meningitis more often than in the temperate zcnes.