SPREAD OF MENINGOCOCCAL INFECTION WITHIN HOUSEHOLDS

Abstract Rates of serogroup-C meningococcal infection (carriage) were studied in households with and without a case of meningococcal disease during an epidemic of sulphonamide-resistant, serogroup-C meningococcal disease in Sao Paulo, Brazil. Carriage-rates were higher (14.2%) in households with a case of meningococcal disease than in households without a case (3.6%). Within households with a case of meningococcal disease, carrier-rates were higher for people sleeping in the house (17.0%) than for other people having household contact with the patient (3.2%). Carriage-rates were highest in households with a case in an infant (37.8%), intermediate in households with a case in a child one to fourteen years of age (17.5%), and lowest in households with a case in an adult (6.9%). Second cases occurred at the same address for 2.6 % of 653 cases in children, while cases in infants and adults were less commonly followed by second cases. The results of these studies support the hypothesis that meningococcal infection is usually introduced into families by adults, spreading subsequently to other members of the family, and usually reaching infants after there is a relatively high " density " of infection in the family.