What is meningitis?
Meningitis is an inflammation of the meninges, membranes that cover the brain and spinal cord. It may be caused by a physical injury, a reaction to certain drugs, or more commonly, infection by certain viruses, bacteria, fungi, or parasites. Some types of cancer and inflammatory diseases, such as lupus, may also cause meningitis. Viral meningitis is the most common form of meningitis in the United States, while bacterial meningitis is the most serious form of the disease. Meningitis is contagious. It can be spread through coughing and sneezing and through close contact. Meningitis can resolve on its own but it can also be a life-threatening emergency, depending on the cause of the infection.
Viral meningitis (also called aseptic meningitis) is the most common type of meningitis and is less severe than bacterial meningitis. Most cases of viral meningitis are caused by enteroviruses that can infect the stomach and small intestine. A small number of cases are caused by other viruses such as herpes simplex virus, human immunodeficiency (HIV) or mumps. Viral meningitis is rarely fatal, and most patients recover from the disease completely.
Bacterial meningitis is the most serious case and can be life-threatening. In the United States, bacterial meningitis mainly affects adults. Most cases of bacterial meningitis are caused by Streptococcus pneumoniae, Neisseria meningitides, and Haemophilus influenzae. Other bacteria, including Escherichia coli and the bacteria that are responsible for tuberculosis and syphilis, can also cause the disease. Bacteria can enter the bloodstream and migrate to the brain and spinal cord, causing acute bacterial meningitis. But the bacteria can also directly invade the meninges, as a result of an ear or sinus infection or a skull fracture.
Meningitis is diagnosed by a lumbar puncture (also called a spinal tap). The doctor takes a sample of cerebrospinal fluid (CSF) from the spine and then the fluid is tested to see if it contains organisms that cause the disease. The doctor may also order other tests, such as blood test, CT scan, or MRI.
The symptoms of meningitis
Meningitis can attack persons of any age, from children to adults. The signs and symptoms of meningitis are always similar and usually develop rapidly, often over the course of a few hours, no matter what the cause. The symptoms include:
- Vomiting
- High fever
- Severe headache
- Stiff neck
- Back pain
- Muscle aches
- Sensitivity of the eyes to light
- Drowsiness
- Confusion
- Loss of consciousness
- Skin rash in some cases, such as in viral or meningococcal meningitis
In infants, the symptoms of meningitis can be more difficult to detect. Infants may not have the symptoms of headache and stiff neck. Instead, they may experience:
- Irritability
- Lethargy
- Loss of appetite
- Inactivity or sluggishness
- Constant crying
- High fever
- Vomiting
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