Functional epidemiology of bacterial meningitis.

The epidemiological behaviour of bacterial meningitis is examined to find clues as to the determinants of the disease. Such an examination has shown that a very limited number of bacteria are able to cause the disease and has suggested some of the virulence characteristics thereof, most notably the presence of certain types of polysaccharide capsules, the predilection of the disease to the first years of life is partially explained by the gradual development of immunity, especially serum antibodies to the capsular polysaccharides. The varying proportion of asymptomatic carriers to those falling ill and the homogeneity of the bacteria in an epidemic speak for the existence of other, as yet unknown virulence factors.