Rubella virus, computer illustration. Each virus particle consists of an RNA (ribonucleic acid) core, surrounded by a protein capsid and a lipoprotein envelope. Spikes in the envelope help the virus to attach to host cells. This virus causes the childhood disease german measles (rubella). It is a mild disease causing a low grade fever, swollen glands, headache and a rash. If a pregnant woman is infected with the virus during the first trimester it causes congenital rubella syndrome (CRS). CRS can lead to miscarriage, stillbirth or birth defects, including deafness and mental retardation.