Meningitis is a disease that is caused by the inflammation of the meninges, the protective membranes surrounding the spinal cord and the brain. While meningitis is most commonly caused by the invasion of viruses or bacteria, it can also be caused by cancer, drugs and physical injury. There are four types of meningitis: parasitic meningitis, bacterial meningitis, viral meningitis and fungal meningitis. Meningitis symptoms include headache, stiff neck, lethargy, nausea and vomiting, altered mental status and sensitivity to light.
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Parasitic meningitis is a very rare form of the disease. It is caused by the Naegleria fowleri parasite, a microscopic amoeba. This parasite enters the body through the nose, where it makes its way to the brain and subsequently destroys it. The disease is also known as primary amoebic meningoencephalitis (PAM).
Naegleria fowleri is commonly found in warm bodies of water in the southern United States, including lakes, rivers, hot springs and discharges from industrial plants. It can also be found in hot water heaters and poorly-maintained or inadequately-chlorinated pools. The parasite does not live in salt water. Naegleria infections can only occur when contaminated water enters the sinuses through the nose. They cannot occur by the ingestion of contaminated water. PAM cannot be transmitted from person to person. Although PAM is extremely rare, it is usually fatal when contracted.
Bacterial meningitis is caused by several types of germs, including Haemphilus influenzae and Listeria monocytogenes. While most people recover from bacterial meningitis, the disease can cause brain damage and hearing loss. In children, it can lead to learning disabilities. The very young, those living in community settings and travelers to the “meningitis belt” in Africa are at an increased risk of developing the disease.
Bacterial meningitis is transferable from person to person by contact with respiratory or throat secretions such as saliva. The bacteria is not transferred through the air or by casual contact with an infected person and are less contagious than those that cause the common cold. Most people who are “carriers” of the bacteria will never get the disease.
Viral meningitis is the most common type. Most of those infected by the virus are able to recover without medical intervention. Some of the viruses that can cause viral meningitis include the mumps virus, the influenza virus, West Nile virus and non-polio enteroviruses.
Although viral meningitis can affect people of all ages, children under five and those who have weakened immune systems or organ transplants are at an increased risk of contracting the disease.
Fungal meningitis is contracted by the spread of a fungus through the bloodstream. The most common cause of fungal meningitis is Cryptococcus. Fungal meningitis is not contagious and most commonly affects premature babies and those with weakened immune systems. Soil contaminated with bird and bat droppings in the Midwestern and the Southwestern United States may contain the Histoplasma or Coccidiodes fungus, respectively, and should be avoided to prevent infection.