Viral and Bacterial
Meningitis is the inflammation of the meninges, the tissues and fluid covering the brain and spinal cord. Meningitis is usually caused by a virus or a bacterium.
Viral meningitis is the most common but least severe form of meningitis. Patients generally recover from viral meningitis without receiving any treatment and have little or no long-term consequences.
In the United States, especially during the summer months, most viral meningitis cases are caused by enteroviruses. This group of viruses includes: enteroviruses, coxsackieviruses, and echoviruses. These viruses are most often spread by fecal contamination (e.g., not washing hands properly after using the toilet or changing a diaper and before eating) or by direct contact with respiratory secretions (e.g., saliva, nasal mucus). There is no vaccine to prevent viral meningitis.
Bacterial meningitis is less frequent but generally more severe than viral meningitis, and may lead to permanent damage (e.g., brain damage, hearing loss) or death. Bacterial meningitis can be treated with antibiotics to prevent serious consequences and to reduce the transmission of disease to other people.
Before the Haemophilus influenzae type b (Hib) vaccine was introduced as part of routine childhood immunizations in 1990, Hib disease was the most common cause of bacterial meningitis in children younger than 5 years. Currently, the leading causes of bacterial meningitis are Neisseria meningitidis (also called meningococcus) and Streptococcus pneumoniae (also called pneumococcus).
The meningococcal vaccine protects against 4 of the 5 most common strains of Neisseria meningitidis, and the newest pneumococcal vaccine protects against 13 strains of Streptococcus pneumoniae. The Hib and pneumococcal vaccines are part of the routine childhood immunization schedule, and the meningococcal vaccine is recommended for adolescents aged 11-12 years, with a booster at age 16 years.