Anthony Komaroff, M.D., is professor of medicine and editor-in-chief of Harvard Health Publications at Harvard Medical School. Dr. Komaroff also is senior physician and was formerly director of the Division of General Medicine at Brigham and Women's Hospital. Dr. Komaroff has served on various advisory committees to the federal government, and is an elected Fellow of the American Association for the Advancement of Science.

Question:

If a person had a mild case of the mumps (only on one side) as a child, can he or she get the disease again?

Answer:

The simple answer is "probably not," but nothing's simple. Mumps is an illness caused by the mumps virus. Once a person is infected, the immune system wipes out the infection and you develop a lifelong immunity. Mumps is a lot less common since a vaccine became available in the 1960s.

Usually the illness begins with feeling tired and achy for a day or two. Then the parotid glands that are located just in front of and below the ears swell up. After a week or more, the illness runs its course. Occasionally, the mumps virus causes more serious illnesses of the brain, testicles, ovaries, heart, kidneys, pancreas, thyroid gland and joints.

Some people who become infected for the first time with the mumps virus don't get sick from it. Others feel a little ill or develop the symptoms of a cold -- but never get the swollen parotid glands that lead to the diagnosis. In other words, you can catch the mumps virus without getting the mumps.

The part of your question that's not simple is that there are some other conditions that can cause swelling of the parotid glands besides the mumps. Several other viruses can do it (even the flu virus) on occasion. So can stones or tumors of the parotid gland, thiazide diuretics ("water pills"), and two unusual diseases called sarcoidosis and Sjogren's syndrome. If one of those conditions caused your parotid gland to swell, and you were mistakenly diagnosed as having the mumps, and then years later you are really infected with the mumps virus, you could "get mumps twice" — except that it really wasn't mumps the first time.