Marijuana use and social networks in a community outbreak of 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.