Joe Walton Jr., age 10, of Meridian, Miss., for his question:

WHAT CAUSES MUMPS?

Mumps is an acute infectious disease caused by a virus that mainly attacks glandular and nervous tissues. An acute disease is one that is brief and severe rather than chronic, or having long duration.

Mumps is spread from person to person by droplets sprayed from the respiratory tract of infected persons, and it is highly contagious. The incubation period of the disease varies from eight to 35 days. One attack usually confers complete immunity.

In children, the first symptoms are usually a mild fever, a feeling of illness and chilliness, loss of appetite and dryness of the throat. This is followed by soreness and swelling around the ears and a higher fever. These symptoms are usually gone by 12 days.

Many persons have mumps in such a mild form that it is not recognized, but they still acquire immunity to the disease.

A preventive vaccine was licensed in 1967 and its use in the United States has brought the annual number of occurrences of mumps to fewer than 5,000.