Household crowding a major risk factor for epidemic meningococcal disease in Auckland children

Background. New Zealand is in its ninth year of a serogroup B meningococcal disease epidemic with annual rates of up to 16.9 cases per 100 000. The hi ghest incidence is in Maori and Pacific Island children in the Auckland reg ion. We conducted a case-control study to identify potentially modifiable r isk factors for this disease. Methods. A case-control study of 202 cases of confirmed and probable mening ococcal disease in Auckland children younger than 8 years of age recruited from May, 1997, to March, 1999, was undertaken, Controls (313) were recruit ed door-to-door by a cluster sampling method based on starting points rando mly distributed in the Auckland region. They were frequency matched with th e expected distribution of age and ethnicity in the meningococcal disease c ases. Results. With the use of a multivariate model and controlling for age, ethn icity, season and socioeconomic factors, risk of disease was strongly assoc iated with overcrowding as measured by the number of adolescent and adult ( 10 years or older) household members per room [odds ratio (OR), 10.7; 95% c onfidence interval (CI), 3.9 to 29.5]. This would result in a doubling of r isk with the addition of 2 adolescents or adults to a 6-room house. Risk of disease was also associated with analgesic use by the child, which was tho ught to be a marker of recent illness (OR 2.4, CI 1.5 to 4.0); number of da ys at substantial social gatherings (10 or more people for > 4 h; OR 1.8, C I 1.2 to 2.6); number of smokers in the household (OR 1.4, CI 1.0 to 1.8); sharing an item of food, drink or a pacifier (OR 1.6, CI 1.0 to 2.7); and p receding symptoms of a respiratory infection (cough, "cold or flu," runny n ose, sneezing) in a household member (OR 1.5, CI 1.0 to 2.5). Conclusion. Some of these identified risk factors for meningococcal disease are modifiable. Measures to reduce overcrowding could have a marked effect on reducing the incidence of this disease in Auckland children.