These Are the 6 Main Types of Meningitis, According to Neurologists and Infectious Disease Doctors

From breathing and walking to thinking and emotional response, your central nervous system (consisting of your brain and spinal cord) controls nearly every bodily function. Keeping that system safe from harm and injury are a trio of membranes known as the "meninges," as well as the clear, cushioning liquid (aka "cerebrospinal fluid") surrounding the brain and spinal cord, says the Centers for Disease Control and Prevention (CDC).

So it's a very big deal when those membranes become inflamed or swollen, a condition called meningitis. The exact type someone develops depends on the cause. Many common types of meningitis are often the result of an infection of the spinal fluid. But other conditions and injuries can cause meningitis, too.

What are the types of meningitis?

"There are many different things that can cause meningitis, ranging from viral, which generally are not life-threatening, to bacterial, which may be," Paul Auwaerter, MBA, MD, clinical director, Division of Infectious Diseases at The Johns Hopkins Hospital, tells Health.

"The kinds of organisms that cause meningitis often are very dependent on someone's age, their underlying health condition, whether they've been immunized," he says, adding that parasites, certain surgeries, being exposed to things like ticks or diseases, can also be factors in developing the condition.

Symptoms of meningitis can come on slowly or suddenly, depending on the type of meningitis, says CDC. Symptoms may include severe headache, fever, light sensitivity, nausea and/or vomiting, neck stiffness that can make it difficult to turn your head or touch your chin to your chest, confusion, and seizures. In some cases, meningitis can also present with what appears to be a purple-red rash under the skin that doesn't blanch, or lighten, when pressed firmly by a glass, according to the UK-based Meningitis Research Foundation.

Here's are the main types of meningitis:

Viral meningitis

Viral meningitis is usually caused by a group of mild respiratory viruses called "enteroviruses," which can be spread through contact with an infected person or object. According to the National Institute of Neurological Disorders and Stroke (NINDS), a division of the National Institutes of Health, enteroviruses can "enter the body through the mouth and travel to the brain and surrounding tissues where they multiply."

For the most part, enteroviruses affect children and are seasonal, circulating in the late summer or early autumn months, and cause mild cold-like symptoms. In some cases, however, they can also lead to meningitis.

"It's not really well known why some people get the meningitis and some people just get a cold, even though the infection, the viruses are the same," Claire Wright, evidence and policy manager at the Meningitis Research Foundation, tells Health.

According to NINDS, other viruses that can lead to meningitis are varicella zoster, (the same virus that causes chickenpox and shingles), herpes simplex type 2, mumps, influenza, and HIV.

While it's possible for anyone to develop viral meningitis, the CDC cites that those at greater risk are children younger than 5, people with weakened immune systems, and babies younger than 1 month old.

Though viral meningitis can lead to severe illness, it typically isn't life-threatening, and treatment is usually limited to convalescence and managing symptoms.

Bacterial meningitis

A meningitis infection caused by bacteria is much more serious. If not treated promptly, bacterial meningitis can cause rapid decline in someone infected by the disease, leading to severe illness and long-term disabilities like hearing loss and brain damage.

"Patients with bacterial meningitis are just sicker," Dhanashri Miskin, MD, neuroimmunologist with Jefferson Health in Philadelphia, tells Health. "If it's not treated in a timely fashion, those patients can die."

While more than 50 different bacteria can cause meningitis, the most common type of bacterial meningitis is pneumococcal, which is caused from the same bacterium as pneumonia. It's also the most serious form of the disease affecting roughly 6,000 people in the US each year, according to the NINDS.

Those at greater risk of contracting pneumococcal meningitis include children under the age of 2 and adults with compromised immune systems.

Meningococcal meningitis is the other most frequent type of bacterial meningitis. Highly contagious, the National Meningitis Association (NMA) says around 600 to 1,000 people contract meningococcal meningitis each year and, of those affected, between 10-15% will die.

Anyone is susceptible to the disease, but according to the NMA, people at greater risk include teens and college students, infants under the age of 1, people living in congregate, or group, settings, and travelers to regions outside of the US that have high rates of meningococcal meningitis.

Anyone suspected of having bacterial meningitis should seek immediate medical attention and treatment typically involves hospitalization and antibiotics targeted to the specific bacteria.

Fungal meningitis

Other less-common types of meningitis include those caused by a fungus. "It's more rare than bacterial," says Dr. Miskin. "You really need to have some kind of underlying immune problem."

According to the CDC, fungal meningitis can occur when a fungal infection located somewhere in the body spreads to the brain or spinal cord.

Typical causes of fungal meningitis include cryptococcus neoformans, which is the most common fungus to cause illness, and is found naturally in the environment. Usually harmless, it can affect people with immune systems compromised by illnesses like cancer or HIV.

Other fungal causes of meningitis are histoplasma, also a non-threatening fungus, except in people with immune conditions, and candida albicans, the same fungus responsible for thrush.

Parasitic meningitis

Another type of infectious meningitis is one caused by a parasite. Though relatively uncommon in the US, parasitic meningitis is more widespread in other parts of the world, according to the NINDS, and is usually linked to a tapeworm.

Parasitic meningitis can also be caused from eating contaminated or undercooked foods like freshwater fish, eels, snakes, chicken, or frogs.

Amebic meningitis

In exceptionally rare cases, certain amoeba found in freshwater likes lakes or rivers, as well as poorly maintained swimming pools, can enter the body through the nose while swimming or diving and infect the brain, leading to amebic meningitis, says NINDS. Like bacterial and parasitic forms of meningitis, amebic can be rapidly fatal if not treated promptly.

Non-infectious meningitis

Certain types of meningitis are caused from something other than a germ or pathogen and aren't transmissible from person to person. These types are known as "non-infectious meningitis."

According to the Merck Manual, symptoms of non-infectious meningitis are similar to those of infectious meningitis and include headache, fever, stiff neck, nausea, vomiting, and light sensitivity, but, in general, tends "to be less severe than acute bacterial meningitis."

One type of non-infectious meningitis can be caused from a chemical reaction. "You can get a chemical meningitis from chronic NSAID use, like ibuprofen," says Dr. Miskin and explains that the patients she typically sees with chemical meningitis are usually those who are undergoing specific treatments for immune disorders or have a history of prolonged painkiller use.

Other potential culprits of chemical meningitis include antibiotics and certain vaccines, which can trigger swelling or inflammation of the meninges.

Overall, however, Dr. Miskin says that the chances of developing a chemical or drug-induced meningitis are relatively low and why they can occasionally lead to meningitis remains a mystery. "We don't really understand why this happens. For unclear reasons, the meninges get irritated by the chronic use of these medications," she says.

Head injuries and certain surgeries can also lead to non-infectious meningitis. "People that undergo a neurosurgery, spinal surgery, can also develop meningitis as a complication," explains Dr. Auwaerter. And, according to the CDC, some cancers and lupus can also be sources of non-infectious meningitis.

Treatment of non-infectious meningitis is specific to the type or cause.

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