Space-time and family characteristics of meningococcal disease and haemophilus meningitis.

Significant space-time clustering was found for cases of meningococcal disease. This result was entirely accounted for by the occurrence of a small number of sibling pairs, and clustering was no longer found when these were omitted from the analysis. Meningococcal disease should still be regarded as potentially communicable between siblings. However, in this region of England the current level of infectivity of the disease outside the family is low. Space-time clustering was not convincingly demonstrated for haemophilus meningitis. This emphasizes that, even with diseases of known microbial aetiology, evidence for such clustering may be difficult to obtain. Only a small number of cases of haemophilus meningitis occurred in single-child families. Cases of single-child families tended to occur in older children than the remainder. Although children under three years of age are most susceptible to haemophilus meningitis, it is likely that the organism is usually introduced into the family by an older sibling.