What is meningitis?

Meningitis usually begins with an infection of the fluid surrounding the brain and spinal cord. The infection can be bacterial, fungal, or viral, and causes the spinal cord and brain membranes to swell. Although rare in developed countries, parasites like Naegleria fowleri can also cause meningitis, as can non-infectious causes like brain injury or cancer. Viral meningitis typically clears up in a few weeks, while bacterial meningitis can sometimes be more serious and should be treated as an emergency. All forms of meningitis should be evaluated as soon as possible by medical professionals.

Picture of meninges
Meningitis usually begins with an infection of the fluid surrounding the brain and spinal cord. The infection can be bacterial, fungal, or viral, and causes the spinal cord and brain membranes to swell. Viral meningitis typical clears up in a few weeks, while bacterial meningitis can sometimes be more serious.

This answer is based on source information from the National Institute of Neurological Disorders and Stroke.

An "itis" is an inflammation of whatever the thing is in the word that's before the "itis".  So meningitis is inflammation of the meninges (mening-itis).  The meninges is a three-part layer of connective tissue that surrounds the brain and descends from the skull to surround the spinal cord all the way down the spine.  Inflammation of the meninges (meningitis) can be caused by a variety of infectious, autoimmune, chemical, or cancerous diseases.

The most common cause of meningitis is viral infection.  A variety of viruses cause meningitis, most of them cause substantial discomfort but are not life-threatening, so-called "viral meningitis".  It is most common in the summer, and patients often have exposure to children (from where they get the enterovirus or other virus causing the infection).  Some viral meningitis is very dangerous, such as that caused by Herpes Simplex Virus.

Bacterial meningitis is a life-threatening emergency.  A variety of bacteria cause the infection, but the most common in adults is Streptococcus pneumonia.  Young adults (often college aged) and military recruits are prone to Neisseria meningitidis meningitis, which is caused by close contact of large numbers of non-immune people.  A vaccine is available to prevent the latter infection.  A variety of other bacteria can cause it as well. Bacterial meningitis presents with intense headache, fever, and a rigid neck--patients can't bend their neck at all.  Viral meningitis tends to be milder, but still there is lots of overlap, so the only way to distinguish life threatening from more benign infection is by doing a spinal tap (AKA lumbar puncture in medical lingo).

Fungal meningitis is seen in certain geographical areas in the US (southwestern US sees lots of cocci meningitis), or in patients with compromised immune systems.  TB can also cause chronic meningitis.

A variety of non-infectious diseases, such as systemic lupus erythematosis, systemic vasculitis of a variety of types, medication reactions (NSAIDs, sulfa drugs, etc.), chemical reactions to blood in the cerebralspinal fluid (such as occurs after a ruptured aneurysm), and leukemias, lymphomas, and certain carcinomas (such as breast) can also cause meningitis.  A spinal tap is necessary to make the diagnosis.

Treatments vary by underlying disease.
Meningitis is an inflammation of the meninges (membrane) that surrounds the spinal cord and brain. There are two types of meningitis: bacterial and viral. Bacterial meningitis can be fatal if not treated promptly. Viral meningitis is less severe and can be easily treated with medication.

(This answer provided for NATA by the Georgia College & State University Athletic Training Education Program.)
Meningitis is swelling of the protective membranes, or meninges, covering the brain and spinal cord. The swelling is usually caused by an infection with a bacteria or virus, but meningitis can also be caused by a fungus. Meningitis caused by a fungus is called fungal meningitis. The severity of illness and the treatment for meningitis differ depending on the cause, so knowing the specific cause of meningitis is important.

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Meningitis is an infection of the tissue layer (meninges) covering the brain and spinal cord. Usually, meningitis is caused by either a virus or bacteria. Meningitis from a virus (viral meningitis) happens more often in the summer. Meningitis from bacteria (bacterial meningitis) happens more in the winter. Fungus can also cause meningitis (fungal meningitis). This is most common in people with a weak immune system.

Boys get meningitis more often than girls. No one knows why. The infection happens more in infants and children less than two years old.
Meningitis is a serious, sometimes life-threatening infection of the protective membranes surrounding the brain and spinal cord. It is one of those very serious diagnoses that if suspected in the emergency room, doctors act on quickly -- usually with a spinal tap to look at and test the fluid around those membranes and immediate intravenous antibiotic treatment. Many different types of germs can cause it. One of the most serious bacterial meningitis infections, meningococcal meningitis, is due to a bacteria called Neisseria meningitides. 

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Brain and Nervous System

A healthy brain and nervous system regulate your body functions so you can have full command over your senses, muscles, and intelligence. Despite the amazing capacities of the human brain and nerves, they are vulnerable to damage ...

just like every other part of our bodies. Strokes, concussions, Alzheimers and many other brain problems affect about 50 million Americans. The multitude of brain injuries and illnesses strike different people based on the risk factors of their genetics, age and lifestyle. The severity of impairment and the availability of treatment vary widely. Knowledge of brain and nerve health has advanced rapidly in recent decades. Many new treatments and medicines are available to treat various disorders. Still, the best thing for your brain is to keep it physically and mentally active while eating nutritious food and getting plenty of social interaction.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.