Rubella, also known as German measles, is a contagious viral infection caused by the rubella virus. It presents with flu-like symptoms including a rash and swollen lymph nodes. While usually mild, rubella infection during pregnancy can cause congenital rubella syndrome in the fetus, resulting in deafness, eye abnormalities, and heart defects. The rubella virus is transmitted through the air via coughs or sneezes and can be prevented through vaccination with the MMR vaccine.