Rubella, also known as German measles, is a mild viral illness caused by the rubella virus. It can cause serious birth defects if a pregnant woman is infected. Norman McAlister Gregg first documented the teratogenic effects of rubella in 1941. The rubella virus is transmitted through respiratory droplets and causes a rash that usually lasts less than a week. Congenital rubella syndrome occurs if an infant is infected in utero and can cause deafness, heart defects, cataracts and other issues. Vaccination with the MMR vaccine is the best way to prevent rubella infection and congenital rubella syndrome.