Marijuana use and social networks in a community outbreak of meningococcaldisease

Background, We examined the role of social networks and marijuana smoking i n a community outbreak of infections due to Neisseria meningitidis. Methods. We interviewed all patients and their contacts. Isolates were test ed by pulsed field electrophoresis and multilocus enzyme electrophoresis. Results. Nine cases of meningococcal disease occurred in the outbreak; isol ates from seven cases with positive cultures were identical. Multiple overl apping social networks were found for case-patients and their contacts. All case-patients were linked by the marijuana-related activities of their con tacts. Conclusion. Investigation of social networks and marijuana exposure might h elp identify close contacts of patients with meningococcal disease and help prevent secondary infections.