Causes of Meningitis
Meningitis is usually caused by infection from a bacterium or virus that has penetrated the nervous system. Most cases of meningitis are caused by bacterial or viral infection, although meningitis can also be caused by other conditions, such as allergic reactions to drugs, fungi, or parasites.
Viral meningitis is responsible for most cases of meningitis and is also usually (although not always) less severe than bacterial meningitis.
Bacterial meningitis is a serious disease that can cause death or permanent brain damage if not treated by a physician immediately. Acute bacterial meningitis is most common in children age 1 month to 2 years. However, localized outbreaks can occur in self-contained groups living in close quarters, such as college students living in dorms or people living in military barracks. Elderly people and those with compromised immune systems (eg, patients with HIV/AIDS) are also at risk.
Although the mortality rate from bacterial meningitis has dropped in recent years, the Centers for Disease Control and Prevention (CDC) report that 10 to 14 percent of people with bacterial meningitis die, and 11 to 15 percent of people who recover are disabled (CDC 2005 [meningococcal disease]).