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 contiguous villages of Deir el-Asad and B'ine in northern Israel (combined population of 11600) in response to a prolonged outbreak of serogroup B meningococcal infection with an overall annual rate of 37.4 cases of infection per 100000 residents. The average case fatality rate in the villages was 23% compared 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 P1.7,16. The persistence of the outbreak with its accompanying public reaction prompted the establishment of an intervention programme that included antibiotic prophylaxis for the whole community with monitoring for pharyngeal carriage of meningococci in a stratified sample of the population. The objectives were to achieve a reduction of carriage of the outbreak strain and to reduce morbidity and mortality. A total of 1036 pharyngeal swabs were taken 1 day before and 6 weeks after treatment. Antibiotic prophylaxis was administered in one dose: children under 5-years-old received ceftriaxone i.m.; all others received oral ciprofloxacin. Overall, 96% of the population received treatment. The carriage rate was 8.3% prior to treatment (three serogroup B:14:P1.7,16), and 1.3% afterwards (one serogroup B:14:P1.7,16). The intervention failed to eradicate carriage of the putative outbreak strain, or to reduce the incidence and fatality rates in the villages. The outbreak finally terminated in late 1996. Public health professionals should bear this experience in mind when faced with prolonged, localized, nonexplosive outbreaks of meningococcal disease associated with low carriage rates of the outbreak strain.