rubella or German measles, acute infectious disease of children and young adults. It is caused by a filterable virus that is spread by droplet spray from the respiratory tract of an infected individual. Rubella is a much milder infection than rubeola (measles) and the rash, appearing after an incubation period of two to three weeks, rarely lasts more than three days. The lymph nodes behind the ears become tender and swollen, but otherwise German measles is almost always uncomplicated. However, during the first trimester of pregnancy it is associated with an increased risk of congenital damage to the fetus, producing stillbirths, abortion, low birth weight, and such malformations as cardiac defects, eye defects (especially cataracts), and mental retardation. During the first 16 weeks of pregnancy the infection has been estimated to carry a risk of fetal damage of between 30% and 35%. Pregnant women who have been exposed to rubella are given gamma globulin in an effort to prevent the disease. Research to develop a vaccine that would confer immunity was spurred by an epidemic of rubella in 1964 and the evidently related rise in the number of birth deformities. A live attenuated vaccine has been developed and is given to girls from 15 months to puberty and often to boys as well. Approximately 13% to 15% of women develop acute arthitis from vaccination. Before the vaccine can be administered to an adult woman it must be determined that she is not pregnant, and the test for the presence of rubella antibodies (which would indicate immunity to the disease from previous exposure) is given. Birth control should be practiced for at least three months after receiving the vaccine. Vaccination has eliminated endemic rubella in the Western Hemisphere.