The authors present experimental-epidemiological data permitting to give an objective quantitative characteristics of the hazard of infection in meningococcus infection (including the carrier state and nasopharyngitis). In 70% of cases meningococcus infection occurred at a distance of less than 0.5 meters. With increase of the distance and reduction of the time of contact the risk of meningococcus infection in a collective body falls to the zero (no such phenomenon is observed in other droplet infections).