Q. How contagious is meningitis in the general population? I'm specifically concerned about the risk of my child's getting this deadly infection in a day care center.

A. Meningitis -- sometimes called spinal meningitis -- is an infection of the thin membrane covering the brain and spinal cord. The most serious meningitis infections are usually caused by bacteria; other, less life-threatening infections are caused by viruses, especially in summer epidemics; rarely, fungi (molds) cause meningitis, usually in sick people with low resistance to infection.

Most cases of meningitis come from bacteria, and children under 5 are the most frequent targets of this potentially deadly disease. The infection usually spreads to the brain via the bloodstream from another site in the body, such as a lung infection (pneumonia). Fortunately, meningitis is an uncommon illness, striking about one in 10,000 persons each year.

Because it can cause brain damage or death -- about 2,000 a year die of meningitis -- it's important to know the symptoms: fever, headache, stiff neck, vomiting, being bothered by bright light, drowsiness, seizures and sometimes a purplish skin rash. No child develops all of these warning signs, which is why it's especially important for your doctor to examine any child who's sick with fever when you aren't sure of the cause.

The most common bacterial cause of meningitis is Hemophilus influenzae (H flu). Adults are generally immune to this infection, but they can transmit it to susceptible children. (Two other bacteria -- Neisseria meningitidis and S. pneumoniae -- are far less common.) H flu is spread by infected droplets from the mouth, for example, through coughing.

Fortunately, meningitis is not very contagious; however, once one child develops meningitis, or any infection due to H flu, the question of preventing other cases of this disease comes up.

There's some controversy about the best way to respond to the threat of H flu infection in children who come into contact with an infected person. Treatment depends on whether the contact occurs in the home or at day care, and on the ages of the children involved.

The Centers for Disease Control and the American Academy of Pediatrics both recommend that in any household with an infected member and a child under 4, everyone take an antibiotic, rifampin, for four days to prevent H flu infection in young children.

In day care centers with children under 2, the CDC recommends that all children and staff take rifampin. Because the risk of others becoming infected when only one child has an H flu infection is uncertain, but probably low -- between zero and 1 percent -- AAP recommends that parents and staff be educated about H flu infection and report any illnesses with fever to their doctor for evaluation. However, both the CDC and AAP recommend antibiotic treatment for everyone once two cases of H flu infection have occurred within a two-month period.

Once two cases of H-flu infection have occurred in a day care center, health experts recommend antibiotics for everyone.

Another preventive measure against H flu infection is the relatively new HiB vaccine, recommended for all children at 18 months of age. However, this vaccine cannot be used in place of rifampin treatment for children recently exposed to someone with H flu infection.

The second most common form of meningitis, that due to the bacterium Neisseria meningitidis, is also unlikely to lead to significant outbreaks in households or day care centers. Rifampin also helps prevent this infection from spreading among contacts. Several vaccines are available for use during epidemics, depending on what type of Neisseria is involved; however, routine vaccination against this uncommon infection is not recommended.

Follow-Up: The Pill

Q. I was interested in your discussion of the long-term effects of birth control pills. I've been taking oral contraceptives -- for six years now -- because my periods were very irregular. I eventually plan to have children and wonder if there's a limit to how long one can safely use the pill.

A. In the past, some doctors used to think it was a good idea to go off the pill every now and then to give your body a chance to return to its natural cycles and avoid prolonged exposure to this medication. Now, most doctors feel it's O.K. to take the pill for years at a time without the need for "medication holidays."

However, your question raises a potential problem, the treatment of irregular periods with birth control pills. You might find that after stopping oral contraceptives you continue to have irregular periods or no periods at all, and difficulty in getting pregnant. In such cases, going off the pill uncovers a problem already present beforehand.

If you fail to have regular periods for months after stopping the pill, you'll need to see your doctor for evaluation.

Jay Siwek, a family physician from Georgetown University, practices at the Fort Lincoln Family Medicine Center and Providence Hospital in Northeast Washington.

Consultation is a health education column and is not a substitute for medical advice from your physician.

Send questions to Consultation, Health Section, The Washington Post, 1150 15th St. NW, Washington, D.C. 20071. Questions cannot be answered individually.