The meninges are the membranes which surround your brain and spinal cord. Meningitis is an inflammation of the meninges. Viral infections are the most common cause.
Bacterial meningitis infections are more serious and require immediate medical treatment. Identifying the specific strain of bacteria is crucial for proper treatment.
Specific bacteria cause specific types of bacterial meningitis.
Streptococcus pneumoniae, which more commonly causes pneumonia or an ear or sinus infection, is the most common cause of bacterial meningitis in the United States.
The bacterium called Neisseria meningitis causes meningococcal meningitis, which commonly occurs when bacteria from an upper respiratory infection spreads to the bloodstream. It is highly contagious and most common among teenagers and young adults. This type of meningitis can cause local epidemics in college dormitories, boarding schools and military bases.
Prior to 1986, Haemophilus influenza type b bacterium was the leading cause of bacterial meningitis in infants and children under the age of six. The introduction of the Hib vaccines, which are part of the routine childhood immunization schedule in the United States, have greatly reduced the incidence of this type of meningitis. Unvaccinated children are at risk, particularly following an upper respiratory infection, ear infection or sinusitis.
Listeria monocytogenes is a type of bacteria found in soil, dust and contaminated foods, like soft cheeses, hot dogs and luncheon meats. This bacterium commonly referred to as listeria, can cause bacterial meningitis among susceptible individuals. Pregnant women, newborns, older adults and individuals with weakened immune systems are most susceptible.
Only 1 to 9 percent of cases of bacterial meningitis are caused by Staphylococcus aureus. It is a complication associated with neurosurgical procedures, brain trauma or medical conditions, like infected intravascular grafts.
The early symptoms of bacterial meningitis can be mistaken for influenza symptoms. The symptoms of meningitis develop over several hours or over one or two days.