Dear Doctor: My daughter's school recently sent home a flier about potential exposure to hand-foot-and-mouth disease. How worried should I be?

Dear Reader: Hand-foot-and-mouth disease (HFMD) is very common. It occurs most often in infants and children younger than 7 years of age and is caused by one of 16 types of enterovirus. Outbreaks are more likely in the late summer and early fall, when children are starting a new year of school or preschool.

Because the viruses that lead to HFMD are largely intestinal, they're usually passed via stool. Small amounts of the virus then make it onto the hands of the child or someone changing the child's diaper. The virus passes from one individual to another when it ends up on food, the fingers or the pacifier of another child, ending up in the mouth. The fecal-oral transmission is the most common way the virus infects others, but it can also be passed through oral secretions, through coughing, and through the fluid from the blisters seen in hand-foot-and-mouth disease.

Regardless, the virus makes its way down to the lower intestine, spreading to the lymph nodes and from there to the rest of the body. The typical time that it takes for the enterovirus to be ingested and for the first symptoms to appear is three to five days.

Symptoms of the disease begin with mouth or throat pain or the refusal to eat. The most striking symptom of hand-foot-and-mouth disease is the blisterlike rash that occurs both within the mouth and on the hands and feet; such blisters can also appear on the legs, arms and buttocks. The lesions are normally not painful and resolve in three or four days. Some species of enterovirus also cause fever, nausea and vomiting. Rarely, enteroviruses can lead to dehydration, viral meningitis or heart inflammation.

I can understand the worry that your school -- and you -- have regarding this infection. As I noted, the incubation period is typically three to five days, but one study of an outbreak at a day care showed that children were infectious up to seven days. And, not to make you overly worried, but some enteroviruses can be passed in the stool up to 10 weeks after infection.

I would ask school officials at which date the infected child began having symptoms of HFMD. If it was more than five days ago, I would be less concerned about your child now developing the disease.

However, because the virus can be shed long after disease, I would stress the importance of hand-washing. If your daughter does get hand-foot-and-mouth disease, the symptoms likely will not last long, and any discomfort can be treated with acetaminophen or ibuprofen. Watch for warning signs of potential complications, such as listlessness, severe headache or neck stiffness. Consult your pediatrician if your child has these symptoms.

Also, if your daughter does become infected, make sure to practice good hygiene at home, so the virus does not pass to you or other family members.

(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'm 55 years old and a former marathon runner. Now my right hip hurts all the time, not only when I walk but also when I'm lying down. I can't even sleep on my right side any more. I was told I need a hip replacement. What does that entail?

Dear Reader: You've described several of the signs and symptoms that make discussing the option of a hip replacement with your doctor a good idea. The goal of the procedure is to address chronic hip pain, increase mobility, return patients to normal activities and restore quality of life. But before you go booking an O.R., let's talk about the operation, as well as possible alternatives.

Hip replacement is a surgical procedure that replaces the diseased or damaged portions of the hip joint with an artificial joint, known as the prosthesis. An estimated 332,000 individuals undergo hip replacement surgery in the United States each year. The surgery is most common among people with osteoarthritis, a degenerative disease that causes joint cartilage to wear away over time. The hip joint becomes rough and ragged, and the ensuing friction causes both pain and stiffness. Rheumatoid arthritis, injury and fractures can also cause sufficient damage to merit a full replacement of the hip joint.

After documenting your symptoms, your doctor will order imaging tests, beginning with an X-ray, to get a detailed image of your hip joint. He or she will be looking for changes to the bone, signs of narrowing of the joint space and the formation of bone spurs. In some cases, an MRI or a CT scan may be ordered as well.

Before focusing on hip replacement as a solution, we help our patients explore other options for dealing with the pain and lack of mobility. These include physical therapy, walking aids, cortisone shots or medications, and pain and/or anti-inflammatory medications. Some people try supplements like glucosamine and chondroitin for pain relief. These and any other nutritional or herbal supplements should always be reported to your physician to guard against possible drug interactions.

Hip replacement surgery takes about one to two hours to perform. An orthopedic surgeon removes the diseased and damaged bone and cartilage and an artificial hip is implanted in its place. A prosthetic socket is implanted into the pelvic bone, and a prosthetic ball replaces the rounded top of the femur. Patients are often surprised when they're asked to sit up and even take a few steps with a walker the day after surgery, which is to deal with the increased risk of blood clots.

After the surgery, patients must work with a physical therapist to rehabilitate the hip. They are given stretching, flexing and strengthening exercises, which they must continue to do on their own to assure the best recovery and results. They must also watch for potential complications like blood clots, infection, dislocation and a discrepancy in leg length.

Full recovery after hip replacement surgery takes three to six months. For the best chance of success, be scrupulous about rehab, and don't try to do too much.

(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 am a 60-year-old man who exercises regularly and takes no medicines. At my last physical exam, my doctor gave me an advance directive form. Do I really need to fill one out?

Dear Reader: Unequivocally, yes. Advance directives are forms providing direction to both family members and the medical community about your wishes in emergencies. More to the point, they specify what your wishes are, in case you can't speak for yourself.

The first part of an advance directive asks whom you would want to make medical decisions for you. Termed a medical power of attorney, this can be your wife, one of your children or a very good friend. It cannot be your doctor. The crucial aspect of this choice is the level of trust you have in your decision maker. If you were to lose decision-making capacity, this person would speak with doctors about your care on your behalf -- becoming both your advocate and the person who chooses resuscitative measures, if any. Not only should you trust the person to whom you give medical power of attorney, you also need to have frank conversations with that person about what you would want.

It sounds as if you're healthy, and thus have a low likelihood of a major illness. But health problems can happen at any time. If you were hospitalized for a heart attack, stroke or a traumatic brain injury, what choices would you want to make? If you were unable to breathe, would you want a tube, attached to a ventilator, placed into your lungs? The answer may be yes -- but not indefinitely. If that's the case, then for how long? Would you consider a tracheostomy, if you were on a ventilator for more than two weeks? Again, the answer may be yes. How about a feeding tube that enters your stomach through your skin? For how long would you want such a measure?

These are not easy topics to consider, or to discuss with the ones you love. But they are important. Ideally, doctors could help with the discussion about end of life, but because the nature of doctors is to treat and heal, many have difficulty discussing end-of-life decisions with their patients. Studies have shown that even with patients who face a life-limiting disease, physicians discuss advance directives only 40 to 45 percent of the time.

One study posed a hypothetical situation in which a man with stage 4 gastric cancer, metastasized to his lung, comes to the emergency room with his wife for severe shortness of breath. The husband and wife in this scenario did not have an advance directive, but their preference was for the husband to remain comfortable and out of the intensive care unit. Only 48 percent of the 27 physicians who treated this hypothetical patient were able to coax out the appropriate information in order to treat him in accordance with his goals and preferences.

Now, I know you don't have gastric cancer, but death is an inevitability. Providing your loved ones, the medical system and yourself direction about your course of care gives you some control over that inevitability.

(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.)