Rubella was considered a mild, benign exanthem of childhood until 1941, when the Australian ophthalmologist Sir Norman Gregg described the profound defects that could be induced in the fetus as a result of maternal infection. Since 1962, when the virus was first isolated, knowledge regarding its extreme medical importance and biological characteris- tics has increased rapidly.
Rubella virus is classified as a member of the togavirus family. It is enveloped and con- tains single-stranded, positive-sense RNA. There is only one serotype, and no extrahuman reservoirs are known to exist. The virus can agglutinate some types of red blood cells, such as those obtained from 1-day-old chicks and trypsin-treated human type O cells.