Carriage of Neisseria meningitidis among household contacts of patients with meningococcal disease in New Zealand

The aims of this study were to estimate carriage prevalence, identify facto rs predictive of carriage, and compare strains of Neisseria meningitidis is olated from patients with meningococcal disease and their household contact s. A total of 954 contacts of 160 patients had a nasopharyngeal swab and an interview relating to factors associated with carriage. The carriage preva lence was 20.4% for Neisseria meningitidis, 11.3% for serogroup B, and 2.6% for serogroup C. Age-standardised carriage was higher in Maori (36.8%) tha n in Pacific Island (21.5%) or European/ other (11.1%) ethnic groups. Facto rs associated with carriage were smoking, with personal smokers (odds ratio [OR] 2.5) and passive smokers (OR 1.6) having a higher carriage risk than those in smoke-free houses; ethnicity, with Maoris having a higher carriage risk than those of non-Maori or non-Pacific Island ethnicity (OR 2.2); gen der, with males at higher risk than females (OR 1.7); and age, with 0-4-yea r-olds less likely and 15-24-year-olds more likely to be carriers than thos e over 25 years. Strong patient-contact clustering by meningococcal strain (chi-square(1)=16.7, P = 0.00004) suggested an important role for the house hold setting in transmission. The low carriage prevalence of serogroup B Ne isseria meningitidis among household contacts may reflect its low transmiss ibility but high virulence. No direct relationship was found between preval ence of ethnic-specific carriage and the incidence of meningococcal disease .