Meninges: dura mater,
arachnoid, and pia mater.

Meningitis is a very serious disease caused by inflammation of the meninges - membrane that cover the brain and spinal cord (central nervous system) consisting of three layers: dura mater, arachnoid, and pia mater.
Meningitis occurs due to infective agents, cancer, physical injury or particular drugs.

An autopsy showing meningitis signs on the
front side of the brain (pus sediments).
It's rare but very dangerous sometimes life-threatening condition usually caused by microorganisms. Those microorganisms are viruses, bacteria, fungi or parasites. They spread through blood and cerebrospinal fluid (CSF).

Since it's usually caused by contagious infections, it can be contagious but it doesn't mean that infected person will get meningitis (he/she will probably get some kind of respiratory or gastrointestinal infection). Also people can have infection that causes meningitis without becoming ill, but they will be able to spread infections to others.

Meningitis can affect everyone without any exceptions, in any age. Anyone who supects of having this disease should prompt for medical help as soon as possible.

The symptoms may include: fever, chills, headache, nausea, vomiting, twitching, light and/or sound sensitivity, drowsiness, confusion, sleepiness, irritability, opisthotonus, sore throat, seizures, delirium, stiff neck, skin rashes, yellowing of the skin (jaundice), poor apetite. 

It's usually diagnosed by examination of blood and cerebrospinal fluid (CSF). Due to its cause there are bacterial, viral and fungal meningitis so the way of treatment depends on disease type.

Bacterial meningitis - very serious form of meningitis commonly fatal if untreated. Treatment consists of antibiotics. Choice of antibiotics depends on bacterial type (usually Streptococcus pneumoniae and Neisseria meningitidis).

Viral meningitis
- can't be treated with antibiotics because they can't kill viruses. Treatment usually includes hospitalization with analgesics (for pain and fever). More serious cases may require the use of antiviral drugs. 

Fungal meningitis - is rarely seen in healthy people but those who have AIDS are on much higher risk. The treatment usually consists of Antifungals and drugs for controlling pain and fever.

Prevention of meningitis is possible only in cases of bacterial form and consists of vaccination.

Pictures from this page were taken from Wikipedia.