A prolonged outbreak of invasive meningococcal disease in an extended Irish Traveller family across three Health Service Executive (HSE) areas in Ireland, 2010 to 2013

Between March 2010 and November 2013 eight laboratory-confirmed cases of serogroup B, invasive meningococcal disease (IMD) were identified in an extended Irish Traveller family across three Health Service Executive (HSE) areas of Ireland. Cases were aged between 5 and 46 months, and were either a cousin or sibling of another case. All eight cases survived. Chemoprophylaxis was given to relevant nuclear family members and close contacts on each occasion, but failed to prevent further cases. Neisseria meningitidis isolates from six cases were highly related, belonging to the ST-41/44 clonal complex, and shared the porA designation 7-2,4. In November 2013, the outbreak control team recommended that directly observed ciprofloxacin chemoprophylaxis be administered simultaneously to the extended family, and that the four component meningococcal B (4CMenB) vaccine be administered to family members aged 2 months to 23 years inclusive and relevant close contacts of the eighth case. Subsequently these recommendations were implemented at three regional clinics. Additionally pharyngeal swabs (n=112) were collected to assess carriage rates of N. meningitidis in this extended family. Pharyngeal carriage of N. meningitidis was detected in 15 (13%) family members. From the epidemiological investigation and carriage study overcrowding was the most likely risk factor identified in this outbreak. To date, the combination of directly observed ciprofloxacin chemoprophylaxis and use of 4CMenB vaccine have controlled the outbreak with no further cases diagnosed.