Failure of mass antibiotic prophylaxis to control a prolonged outbreak of meningococcal disease in an Israeli village

In January 1994 mass antibiotic prophylaxis was undertaken in the contiguou s villages of Deir el-Asad and B'ine in northern Israel (combined populatio n of 11600) in response to a prolonged outbreak of serogroup B meningococca l infection with an overall annual rate of 37.4 cases of infection per 1000 00 residents. The average case fatality rate in the villages was 23% compar ed with 11% in Israel during the same period. Neisseria meningitidis group B was identified in 9 of 13 (69%) cases. Seven of these were subtype P1.7,1 6. The persistence of the outbreak with its accompanying public reaction pr ompted the establishment of an intervention programme that included antibio tic prophylaxis for the whole community with monitoring for pharyngeal carr iage of meningococci in a stratified sample of the population. The objectiv es were to achieve a reduction of carriage of the outbreak strain and to re duce morbidity and mortality. A total of 1036 pharyngeal swabs were taken 1 day before and 6 weeks after treatment. Antibiotic prophylaxis was adminis tered in one dose: children under 5-years-old received ceftriaxone i.m.; al l others received oral ciprofloxacin. Overall, 96% of the population receiv ed treatment. The carriage rate was 8.3% prior to treatment (three serogrou p B:14:P1.7,16), and 1.3% afterwards (one serogroup B:14:P1.7,16). The inte rvention failed to eradicate carriage of the putative outbreak strain, or t o reduce the incidence and fatality rates in the villages. The outbreak fin ally terminated in late 1996. Public health professionals should bear this experience in mind when faced with prolonged, localized, nonexplosive outbr eaks of meningococcal disease associated with low carriage rates of the out break strain.