Measles, mumps, and rubella are illnesses caused by viruses. The most severe of the three is measles. It is characterized by a high fever (often up to 104ºF) and a rash. Complications of measles include ear infections, pneumonias, and encephalitis (inflammation of the brain).
Mumps is a milder illness that usually causes swelling of the salivary glands, especially the parotid glands in the mouth that produce saliva. The swelling of the parotid glands gives a person with mumps the classic “chipmunk” face. In men, swelling of the testicles (orchitis) may also occur, which rarely leads to sterility.
Rubella, or German measles, is the mildest illness of the three. It usually causes a low-grade fever, a generalized rash, and some swelling of lymph nodes. Occasionally, adults will have temporary arthritis associated with their infection. The major issue with this illness is that if a pregnant woman develops rubella during pregnancy, she may suffer from a miscarriage or stillbirth, or the baby may suffer from significant birth defects.