Causes of Meningitis
Viruses and bacteria that spread to or directly infect the central nervous system cause most cases of infectious meningitis.
About 90% of cases of viral meningitis are caused by one of the enteroviruses (e.g., coxsackievirus, echovirus, poliovirus). Mumps, herpesvirus, and arboviruses (transmitted by insect bites) also may cause viral meningitis. About 30% of mumps cases in people not vaccinated for the disease develop meningitis.
Common causes of bacterial meningitis include Streptococcus pneumoniae, Neisseria meningitides, Staphylococcus aureus, Escherichia coli, and Staphylococcus epidermidis. Prior to the 1990s, Haemophilus influenzae type b was the primary cause, but widespread vaccination (Hib vaccine) has greatly reduced the incidence of this infection.
Candida albicans, Crytococcus neoformans, and Histoplasma are often involved in cases of fungal meningitis.
Noninfectious Meningitis Causes
Causes of noninfectious meningitis include the following:
- Carcinomatosis (widespread metastatic cancer)
- Contaminated water (may contain parasites)
- Head injury, birth defect of the skull, brain surgery (may result in infection of the meninges or cerebrospinal fluid)
- Medications such as nonsteroidal anti-inflammatories (e.g., ibuprofen, naproxen) and antibiotics (e.g., Bactrim®, Septra®).
