Neisseria meningitidis causes the invasive diseases of meningitis and meningococcemia. Because the rate of invasive Haemophilus influenzae disease has declined, N. meningitidis is now the leading cause of bacterial meningitis in children and young adults in the United States. Most cases of the disease are random, but secondary cases occasionally occur among persons in close contact with the primary carrier.
Diaz reviewed epidemiology and control of meningococcal disease. Attack rates are highest in children three to 12 months of age. The disease occurs sporadically throughout the year, with seasonal peaks occurring during winter and early spring. Asymptomatic upper respiratory tract colonization occurs in up to 5 percent of the U.S. population.
Meningococcal infection is not highly contagious. The infection is transmitted from person to person through direct contact with nose and throat secretions. Well persons may carry the bacteria transiently and spread it to others. Persons with immunosuppression are at increased risk for invasive meningococcal disease. Other risk factors include household crowding, concurrent upper respiratory tract infection, low socioeconomic status, bar patronage and active and passive smoking. Outbreaks in the United States have been identified as being organization-based, such as a common affiliation through a university or correctional facility but no close contact with each other, or community-based, with people living in the same area who do not have close contact with each other.
Prevention of meningococcal disease is achieved through antimicrobial prophylaxis of those persons in close contact with the primary carrier. Close contacts are defined as household members, child care center classmates and teachers, or anyone who is directly exposed to oral secretions of the primary carrier through kissing, sharing of drinks, eating utensils or cigarettes. The drug of choice for prophylactic treatment is rifampin, in a dosage of 10 mg per kg per dose orally every 12 hours for two days (maximum: 600 mg per dose). In infants less than one month of age, 5 mg per kg per dose orally every 12 hours for two days is the most common prophylactic regimen. In children less than 12 years of age, a single intramuscular dose of ceftriaxone, 125 mg, and in children 12 years of age or older, 250 mg, is given. In adults, a single oral dose of 500 mg of ciprofloxacin is indicated.
A vaccine is available to control serogroup C meningococcal outbreaks. However, it is not recommended for routine use because the resultant immunity is of limited duration, and it works poorly in children less than 18 to 24 months of age. The vaccine is recommended for travelers to countries in which the disease is hyperendemic or endemic. New generations of vaccines are currently being developed.