Babies who are very ill may actually have a lower than normal temperature. Causes Most meningitis is caused by either bacteria or viruses. A number of different types of bacteria can cause acute bacterial meningitis. This bacterium is the most common cause of meningitis in adults and children. You may also have this type of bacteria in your lungs where it causes pneumonia .
Pneumococcal meningitis can also result from an ear infection or head injury.
This bacterium is the second most common cause of meningitis in children under age 5. Meningococcal meningitis is also increasing among college-aged students, especially those living in dormitories. Meningococcal meningitis commonly occurs when bacteria from an upper respiratory infection enter your bloodstream. It's highly contagious and may cause localized epidemics in boarding schools and on military bases. B. The vaccine is only effective for 3 to 5 years, however.