•  Immunizations •  Your Amazing Brain (Animated Guide)

Underneath your hard skull, your brain is protected by three layers of membranes called the meninges. Between the two layers closest to the brain is a liquid called cerebrospinal fluid that cushions the delicate organ. The system generally works well to protect the brain from hard knocks and infections, but viruses and bacteria can sometimes break through the body's defenses. If an infection reaches the spinal fluid or the outer covering of the brain, the meninges can become inflamed. This condition is called meningitis.

Most of the time, meningitis comes in two basic varieties: viral and bacterial.

A viral infection, the more common form, is rarely serious and usually clears up in about 10 days. Usually, the viruses that cause meningitis are the same ones that cause stomach flu. Less commonly, certain types of fungus, drug and chemical reactions, and cancer cells can cause meningitis.

About 10,000 cases of viral meningitis are reported in the United States each year, but the actual number may be closer to 75,000. The disease is especially common among babies and young children. The risk of viral meningitis generally declines with age, although it can climb again as people enter old age.

Bacterial meningitis is less common but far more serious. Without treatment, it can be fatal. Patients who survive severe bacterial meningitis may be permanently disabled with deafness, severe brain damage, or paralysis.

Several types of germs can cause bacterial meningitis. The two most common are called pneumococcus (Streptococcus pneumoniae) and meningococcus (Neisseria meningitidis). Another bacterium that causes meningitis, mainly in children, is Hib (Haemophilus influenza type b). In newborns and infants, group B strep, E. coli, and listeria are frequent causes of bacterial meningitis.

Meningococcal illnesses, including meningitis, strike 1,000 to 2,600 people each year, mostly infants, teenagers, and young adults. This germ is highly contagious and can spread easily among people living in tight communities, such as college dormitories or military bases. Pneumococcal meningitis, which is most common in infants and young children, sickens up to 6,000 people each year.

Children, young adults, and seniors are at highest risk for meningitis. People who spend time in close contact are most at risk of catching meningitis germs, including military personnel, students who live in dorms, kids in day care, and people in nursing homes. Others who come in contact with people in these groups, such as health care workers and childcare providers, are also at higher risk.

It usually takes more than casual contact to get infected. Meningitis germs can be spread by sneezing, coughing, kissing, or other close contact. Sharing dishes, food, and towels can also spread the infection. Some bacteria can reach the brain through an ear infection or skull fracture. Bacteria can also reach your bloodstream from an upper respiratory infection. And according to a 2003 study in the New England Journal of Medicine, children with certain types of cochlear implants may be at higher risk of getting bacterial meningitis.

Even doctors admit that the symptoms of meningitis can be confusing. Symptoms can vary from one person to another. And although viral meningitis tends to be milder than the bacterial kind, doctors usually need to run special tests to tell the difference.

The signs of meningitis generally build over one or two days, but they can also hit suddenly. Classic symptoms include a stiff neck combined with high fever, severe headache, and confusion or disorientation. Other symptoms can include nausea, vomiting, sensitivity to light, lack of appetite, and seizures. In some types of meningitis, a skin rash might appear.

Infants with meningitis may cry constantly or may be unusually irritable. They may show no interest in food, and they can be hard to wake up. In very young babies, the soft spot at the top of the head might bulge out. As the infection gets more severe, an infant may have spasms that stretch the body out as far as it can go.

Depending on the symptoms, your physician may be able to tell if the infection is viral or bacterial, but the answer isn’t always obvious. If there's any doubt, the doctor will probably assume the worst and treat it as a bacterial infection. Testing a sputum sample can tell which germs are in your throat, but they may not be the same as the ones in your cerebrospinal fluid. A blood test may also be helpful.

For a definite diagnosis, doctors will test the cerebrospinal fluid (CSF). A sample of fluid is removed by a procedure known as a lumbar puncture or spinal tap. Although it sounds painful, a local anesthetic keeps discomfort to a minimum. The sample is sent to the lab for gram staining to quickly identify different types of bacteria; bacterial culture, which takes several days; or PCR testing, which picks up DNA sequences and can determine whether the infection is viral or bacterial.

If you think you or your child has meningitis, get to a doctor immediately. If it turns out to be bacterial, quick treatment with antibiotics is crucial. The antibiotics are delivered through an IV to attack the germs as aggressively as possible. Doctors might need to drain fluid from infected sinus cavities or from between the brain and meninges. Even with treatment, 10 percent to 15 percent of patients with bacterial meningitis will die.

In some cases of bacterial meningitis, doctors may prescribe antibiotics for all close contacts of a patient, such as family members, other children in daycare, or other people living in the same household.

Viral meningitis generally goes away on its own. (Because antibiotics only work against bacteria, they won’t help a person with viral meningitis.) Most viral patients don’t need anything more than rest, lots of fluids, and perhaps some acetaminophen (Tylenol) to reduce fever and body aches. (Note: Never give aspirin to a child or teenager who might have a viral infection. Aspirin could trigger Reye’s syndrome, a rare but serious condition.)

Fortunately, the most common forms of bacterial meningitis can often be prevented with immunizations, even though they don’t necessarily offer 100 percent protection.

A vaccine against the seven most common pneumococcal bacteria (PCV7) is part of the regular immunization schedule recommended for children under age 2. Babies also routinely receive a vaccine against Hib. Both are four-shot series typically given at 2 months, 4 months, 6 months and 12 to 15 months.

The MCV4 vaccine against four types of meningococcal bacteria is now routinely given to children at age 11 or 12. It is sometimes given to younger children who are at high risk because of lowered immunity or other reasons. If they missed it earlier, teenagers and young adults can get the one-time MCV4 shot anytime, ideally before starting high school, moving into a school or college dormitory, or joining the military. A growing number of schools and colleges now require proof of MCV4 vaccination before students enroll.

Another immunization PPV (pneumococcal polysaccharide vaccine, similar to the PCV7 vaccine for children), is recommended for all people over age 65 and for high-risk children and adults aged 2 to 64.

You can also try protect yourself by avoiding these germs in the first place. Wash your hands often, and show your children how to do the same. Don't share personal items such as toothbrushes, eating utensils, or cigarettes. You can also keep your immune system strong by getting lots of rest and exercise and by eating a healthy diet with plenty of fresh vegetables, fruits, and whole grains.

-- Chris Woolston, MS, is a contributing editor to Consumer Health Interactive. A former staff writer for Hippocrates magazine, he has written for Health, Prevention, and other journals. He writes The Healthy Skeptic, a biweekly health and medical column in the Los Angeles Times. He is also the co-author of Generation Extra Large: Rescuing Our Children from the Epidemic of Obesity (Perseus paperback, 2006).

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First published June 3, 2008
Copyright © 2008 Consumer Health Interactive

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