The tough outer membrane is called the dura mater, and the delicate inner layer is the pia mater. The middle layer is the arachnoid, a weblike structure containing the fluid and blood vessels covering the surface of the brain. Viral infections are the most common cause of meningitis, followed by bacterial infections and, rarely, fungal and parasitic infections. Because bacterial infections can be life-threatening, identifying the cause is essential.
Bacteria that enter the bloodstream and travel to the brain and spinal cord cause acute bacterial meningitis. But it can also occur when bacteria directly invade the meninges. This may be caused by an ear or sinus infection, a skull fracture, or — rarely — some surgeries.
Viral meningitis is usually mild and often clears on its own. Most cases in the United States are caused by a group of viruses known as enteroviruses, which are most common in late summer and early fall. Viruses such as herpes simplex virus, HIV , mumps virus, West Nile virus and others also can cause viral meningitis. Slow-growing organisms such as fungi and Mycobacterium tuberculosis that invade the membranes and fluid surrounding your brain cause chronic meningitis.
Chronic meningitis develops over two weeks or more. The signs and symptoms of chronic meningitis — headache, fever, vomiting and mental cloudiness — are similar to those of acute meningitis. Fungal meningitis is relatively uncommon in the United States. It may mimic acute bacterial meningitis. It's often contracted by breathing in fungal spores that may be found in soil, decaying wood and bird droppings. Fungal meningitis isn't contagious from person to person.
Cryptococcal meningitis is a common fungal form of the disease that affects people with immune deficiencies, such as AIDS. It's life-threatening if not treated with an antifungal medication. Even with treatment, fungal meningitis may recur. Parasites can cause a rare type of meningitis called eosinophilic meningitis.
Parasitic meningitis can also be caused by a tapeworm infection in the brain cysticercosis or cerebral malaria. Amoebic meningitis is a rare type that is sometimes contracted through swimming in fresh water and can quickly become life-threatening. The main parasites that cause meningitis typically infect animals. People are usually infected by eating foods contaminated with these parasites. Parasitic meningitis isn't spread between people. Meningitis can also result from noninfectious causes, such as chemical reactions, drug allergies, some types of cancer and inflammatory diseases such as sarcoidosis.
Meningitis complications can be severe. The longer you or your child has the disease without treatment, the greater the risk of seizures and permanent neurological damage, including:. Common bacteria or viruses that can cause meningitis can spread through coughing, sneezing, kissing, or sharing eating utensils, a toothbrush or a cigarette. Meningococcal conjugate vaccine.
The CDC recommends that a single dose be given to children ages 11 to 12, with a booster shot given at age If the vaccine is first given between ages 13 and 15, the booster is recommended between ages 16 and They have the bacteria, but they do not develop symptoms. Living in a house with either a carrier or someone who has meningitis increases the risk. It is important to follow the recommended vaccination schedule to prevent meningitis.
Recurrent bacterial meningitis is possible but rare. Studies show that 59 percent of recurrent cases are due to anatomical defects, and 36 percent occur in people with a weakened immune system.
Treatment for bacterial meningitis normally involves admission to the hospital, and possibly an intensive care unit. Antibiotics are essential, and these may be started before the results of tests come back, possibly before arrival at the hospital. Treatment includes :. As several types of bacteria can cause bacterial meningitis, so a range of vaccines is necessary to prevent infection.
The first vaccine was created in to protect against 4 of the 13 subtypes of N. A survey of 17 million people in the U. The meningococcal vaccine is the primary vaccine in the U. All children should have this at the age of 11 to 12 years and again at 16 years, when the risk of infection is higher. The Hib vaccine protects children against H. Before its introduction in the U. Influenzae infected over 20, children under 5 years annually, with a 3 to 6 percent mortality rate. Widespread vaccination has reduced the incidence of bacterial meningitis by over 99 percent.
The Hib vaccine is given in four doses at the ages of 2, 4, 6, and 12 to 15 months. Side effects of the vaccines may include redness and soreness at the site of the injection and a fever. Always check with a doctor to ensure that no allergies to any part of the vaccinations are present. To prevent the spread of bacterial meningitis and other diseases, it is important to practice good hygiene, such as frequent handwashing.
Vaccines are available that target many of these bacteria. For this reason, it's important to know what's causing meningitis.
Even though all types affect the same area of the body, they can have different outcomes and need different treatments. Experts don't always know why meningitis happens.
Some people get it when their immune system is weak or they've recently been sick. A head injury may also increase risk. Bacterial meningitis is more common in infants under 1 year of age and people ages 16 to College students living in dorms or other close quarters are at increased risk. Also at risk are adults with certain medical problems, including those without a spleen.
Symptoms typically come on quickly, in as little as a couple of hours or up to a day or two. If you think you or your child may have meningitis, go to an emergency room right away. To diagnose this condition, a healthcare provider will do a spinal tap also called a lumbar puncture to take a sample of fluid from around the spinal cord. The fluid is then tested for bacteria.
The healthcare provider will also ask about your symptoms and do a physical exam. Prompt treatment of bacterial meningitis is crucial. It can save your life. Once the type of bacteria has been identified, you'll start taking antibiotics. Antibiotics are given through a needle placed into a vein usually in the arm or hand. They may also be given along with a corticosteroid to help reduce inflammation and swelling.
Treatment also includes plenty of fluids to prevent dehydration.
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