Susan Lewis, age 11, of Dillon, S.C., for her question:

WHAT IS MONONUCLEOSIS?

Mononucleosis is a mild infectious disease marked by a large increase in the number of abnormal lymphocytes, a type of white blood cell. The disease got its name from these single nucleus cells.

Young adults are the ones who most frequently come down with mononucleosis, although the disease can also strike children and older people.

A virus causes the disease and direct contact between people can spread it. There's a fever, chills, a sore throat and fatigue. And there's also a swelling of the lymph glands.

Most doctors recommend mild to complete bed rest for a person with mononucleosis. Most patients recover within three to six weeks.