Viral disease with a usually mild course, except in women in the first 20 weeks of pregnancy, in whom it can cause fetal birth defects (of eyes, heart, brain, and large arteries) or death. Sore throat and fever are followed by swollen glands and a rash. Up to 30% of infections may have no symptoms. Lifelong immunity follows infection. Encephalitis is a rare complication. Rubella was not distinguished from measles (rubeola) until the early 19th century and was not known to be dangerous until 1941. The virus was isolated in 1962, and a vaccine became available in 1969.