Rubella viruses are single-stranded ribonucleic acid viruses, which are surrounded by a lipid-containing membrane. From the taxonomic point of view, these serologically uniform viruses belong to the family of Togaviridae, and to the genus Rubivirus. After birth, infection with rubella virus occurs through inhalation of contaminated droplets. In children infected after birth, rubella viruses usually cause uncomplicated diseases that are associated with an unspecific rash (postnatal rubella). Rubella virus infections in adults might be more severe and can be accompanied by complications such as joint pain and inflammation in the joints. Rubella virus infection during pregnancy can lead to the infection of the fetus. In the first and second trimester of pregnancy, fetal rubella infection often lead to severe abnormalities of the newborn, which are summarized as rubella embryopathy or congenital rubella syndrome. One of these disorders, the Gregg syndrome, is associated with serious damage to heart, ears and eyes of the newborn. Therefore, in suspected cases of rubella virus infection during pregnancy, or after contact of a pregnant woman with an infected person, a serological diagnosis must be performed. The diagnosis of an acute rubella virus infection usually consists of the detection of rubella-specific IgM. Critical to avoiding a rubella virus infection is the immune prophylaxis, for which a live attenuated vaccine, usually given as trivalent vaccine against measles, mumps and rubella (MMR vaccine), is available. Since the introduction of the rubella vaccination in the 1970s, in many areas of the world the number of rubella diseases has declined dramatically. Nevertheless, rubella is still widespread in some countries, and still occurs in Germany. Postnatal rubella virus infections can be treated symptomatically. A specific (antiviral) therapy is not available.