Dear Doctor: One of the schools in my area has been the focus of news reports about a bacterial meningitis case. How contagious is this disease?

Dear Reader: Bacterial meningitis cases in school-age children, adolescents and college students are predominately caused by two different organisms: Streptococcus pneumoniae and Neisseria meningitidis. Streptococcus causes nearly 50 percent of meningitis between the ages of 2 and 18, while people in their teens and college years face an increased risk of meningitis caused by Neisseria meningitidis. In fact, 46 percent of meningitis cases between ages 11 to 17 are due to N. meningitidis.

The Streptococcus pneumoniae bacterium is spread by close contact with people who cough or sneeze. Upon inhalation, the bacteria adhere to the back of the nasal passage in an area called the nasopharynx. Normally, there the bacteria sit, colonizing the nasopharynx without causing any problems. A study of 2,799 Italian children younger than 7 years of age found that 8.6 percent had S. pneumoniae colonizing the nasopharynx; the biggest risk factor for colonization was a sinus infection over the previous three months.

In most people with this colonization, the immune system keeps the bacteria from invading the cells of the body. However, when the immune system is weakened or when the body is fighting a viral infection, such as influenza, the bacteria can then invade the cells. From there, the bacteria can enter the bloodstream and cross through the blood-brain barrier, replicating readily in the cerebrospinal fluid, leading to the symptoms of meningitis.

The Neisseria meningitidis bacterium is passed from one person to another by secretions from coughing or by saliva from kissing. It's also passed easily among people in close contact. Like Streptococcus, Neisseria also settles in the nasopharynx, where the immune system similarly keeps the bacteria from invading into the cells of the body. People can carry the bacteria for several months within their nasopharynx and unwittingly pass it on to others.

In fact, 5 to 10 percent of people in the United States carry this bacteria in the nasopharynx. Military recruits in closed quarters can have carrier rates up to 40 percent. College students in dormitory situations have carrier rates of 14 to 34 percent. If one person develops meningitis from N. meningitidis, other people with whom they are in close contact are at greater risk.

Again, the bacteria that cause meningitis are quite contagious, but a person's general risk of developing the illness is very low. In addition, children and adolescents are vaccinated for three types of bacteria that can lead to meningitis: Streptococcus pneumoniae, Neisseria meningitidis and Haemophilus influenzae type b. These vaccinations have significantly decreased the rates of meningitis, so make sure that your child gets these vaccinations.

Lastly, if your child has been exposed to somebody with meningitis, watch for fever, neck stiffness and lethargy. If he or she begins to exhibit these symptoms, all potential signs of meningitis infection, take him or her to a doctor as soon as possible.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: Is it safe to use an insect repellent with DEET on my 5-month-old? Here in Tennessee, we're approaching prime mosquito season, and we want our little boy to be able to play outside without getting all bitten up.

Dear Reader: There's nothing like the thin, high whine of a mosquito to let you know your picnic or hike or nap on the porch is about to be ruined by slapping, itching and scratching. Unfortunately, mosquitoes are also known carriers of serious diseases. West Nile virus and St. Louis encephalitis have been diagnosed in some areas of the United States. The Zika virus, while rare in the United States, is also a mosquito-borne disease.

According to the Centers for Disease Control and Prevention, insect repellents that contain DEET are safe to use on children 2 months old and older. DEET, which is shorthand for (deep breath) N,N-diethyl-meta-toluamide, is the active ingredient in a wide array of insect repellents.

DEET does not kill insects. It works by blocking the sensory mechanisms that tell insects that something delicious is nearby. Instead of detecting the chemical markers we humans emit in our breath and sweat, the bugs smell ... nothing. They pass us by.

There are specific guidelines you should follow when using DEET on a child. The CDC recommends that you never use a product with a concentration of more than 30 percent DEET. The percentage of DEET in a product doesn't make the insect repellent stronger or more potent; what that number measures is the length of time the insect repellent will be effective.

Products with concentrations of 10 percent keep bugs at bay for about two hours. Those with 21 to 25 percent DEET provide between five to eight hours of protection. And, please note -- current recommendations state that children should not have more than one application of DEET per day.

Although some insect repellents with DEET have sunscreen mixed in, it's best to steer clear of those. Sunscreen must be reapplied throughout the day to be effective. However, since kids should only get one application of DEET per day, the mixed product is of limited use. It's best to start with a base layer of sunscreen and then add insect repellent. You can then add more sunscreen throughout the day as needed.

Insect repellent should be applied to exposed skin and to clothing. When using a spray, apply it outdoors and be sure to keep it away from food. Make sure neither you not your child inhales the product.

We find that while a spray works well on clothes, insect repellent wipes are great for precise applications to a child's wriggling body. And never put insect repellent on a child's hands, which so often find their way into mouths and eyes. Once back indoors, wash the treated skin with soap and water. Treated clothes should be washed before wearing again.

One final thought: While repellents are a great tool, give them a boost by keeping kids in long-sleeved pants and shirts when in the buggy great outdoors.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)

Dear Doctor: I have played tennis for many years, but have been unable to play over the last year, due to tennis elbow. Would acupuncture help?

Dear Reader: Lateral epicondylitis, or tennis elbow, is a tendon inflammation at the elbow. You don't have to play tennis to develop the condition, but the specific motion of hitting a ball with a tennis racket is, unfortunately, an effective way of doing so. There are many different types of treatment for tennis elbow, including anti-inflammatory medications, physical therapy, ultrasound, platelet-rich plasma injections and steroid injections.

As for acupuncture, a review of multiple studies published in the British Journal of Sports Medicine attempted to answer your question. One of the studies found significant pain relief with acupuncture compared with placebo. Overall, reduction of pain was 55.8 percent in the acupuncture group and 15 percent in the placebo group.

However, another study showed an immediate improvement of symptoms with acupuncture after two weeks, but no difference after two months compared to placebo. Lastly, a study comparing acupuncture to ultrasound therapy for tennis elbow found no difference between the two treatments.

Overall, the authors concluded that acupuncture was helpful for tennis elbow, but it did not have a sustained response, lasting only two to eight weeks.

A 2015 study combined results from six different studies. Two of the studies compared real acupuncture with sham acupuncture, which involves placing the needle in non-traditional acupuncture points at random. The authors found a benefit with standard acupuncture compared to sham acupuncture. Also, there were conflicting studies on whether acupuncture with electrical stimulation was beneficial or not.

One other review from 2002 showed that acupuncture for tennis elbow did have immediate benefit, but the authors could not conclude a long-term benefit.

Now, I have to acknowledge that I've been performing acupuncture for tennis elbow for the last 12 years and have seen that the treatment has been beneficial for the majority of patients. I have treated these patients with non-traditional acupuncture points at the tendon insertion of the elbow and have used electrical stimulation. I also add traditional acupuncture points. It is difficult for me to assess how much of the benefit is from the acupuncture, how much is from physical therapy and how much is just the tincture of time.

The studies do appear to show pain relief, but I feel that acupuncture should be combined with physical therapy. The bottom line: Acupuncture is one of many therapies that can help the pain of tennis elbow.

(Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)