Meningococcal Disease
Background. We examined the role of social networks and marijuana smoking in a community outbreak of infections due to Neisseria meningitidis.
Methods. We interviewed all patients and their contacts. Isolates were tested by pulsed field electrophoresis and multilocus enzyme electrophoresis.
Results. Nine cases of meningococcal disease occurred in the outbreak; isolates from seven cases with positive cultures were identical. Multiple overlapping social networks were found for case-patients and their contacts. All case-patients were linked by the marijuana-related activities of their contacts.
Conclusion. Investigation of social networks and marijuana exposure might help identify close contacts of patients with meningococcal disease and help prevent secondary infections.

Invasive meningococcal disease is the leading cause of bacterial meningitis in children and young adults in the United States, with an estimated 2,600 cases each year. Although most cases occur sporadically, between 10 and 15 outbreaks of meningococcal disease are reported in the United States annually. Timely antimicrobial chemoprophylaxis of close contacts is the primary method of preventing meningococcal disease. Quadrivalent polysaccharide meningococcal vaccine is recommended for control of serogroup C meningococcal disease outbreaks.

From December 12, 1998, to January 4, 1999, meningococcal disease was diagnosed in nine patients in a rural Florida town of approximately 33,000 residents. One patient died. We administered antibiotic chemoprophylaxis to close contacts of case-patients and implemented a vaccination campaign in which 13,500 persons aged 2 to 22 were vaccinated.

Initial investigations revealed that marijuana use was prevalent among the patients and their household members. Identifying close contacts became difficult because patients and their families seemed hesitant to reveal information on contacts. We therefore intensified our investigation of the social networks of the case-patients to better identify persons who might need chemoprophylaxis but who might not have been found using conventional methods.