What Is Meningitis?
Meningitis is an infection that causes the membranes that surround the spinal cord and the brain (called meninges) to become inflamed. It also causes the surrounding cerebrospinal fluid to become irritated and inflamed, according to the Mayo Clinic. This inflammation leads to significant swelling around the brain, resulting in symptoms such as stiffness of the neck, persistent headache and a fever. The prognosis for meningitis can be wide-ranging. Some infections can clear up without treatment within weeks and others can be fatal.
Viral Infections
According to the Mayo Clinic, the most common cause of meningitis is a viral infection. Enteroviruses are the most common type of viral meningitis infection, causing as many as 90 percent of all viral meningitis infections. Other viruses that can cause meningitis include the herpes virus, mumps, influenza, measles and arboviruses, says the U.S. Centers for Disease Control and Prevention. Typically, viral meningitis is the milder form of the infection and gets better without treatment.
Bacterial Infections
Bacteria can also cause meningitis. Neisseria meningitides, streptococcus pneumoniae, listeria monocytogenes and haemophilus influenzae are all possible types of bacteria that can cause meningitis, the Mayo Clinic says. Group B streptococcus is another bacteria that can cause meningitis, says the CDC. These bacteria find their way into the blood, flow to the spinal cord and brain and cause inflammation. An infection in the ear or sinuses, as well as a skull fracture, can also cause bacterial meningitis.
Fungal Infections and More
Though it's quite uncommon, fungi can also cause meningitis. It's called cryptococcal meningitis. Most often, it strikes people with a compromised immune system, such as people with AIDS. It can be easily treated with antifungal medications but can be fatal without treatment.
Other possible causes of meningitis include cancer (tumors) and an allergic reaction to medications. Diseases that cause inflammation, such as lupus, can also cause meningitis, the Mayo Clinic says.
