Which one of the following viruses is the leading cause of congenital malformations?

The rabies virus is transmitted by the bite of a rabid animal. It almost always causes a fatal encephalitis if untreated. Postexposure treatment includes use of a killed vaccine and human rabies globulin (HIG). Rhinoviruses are the most prominent cause of the common cold. Many serotypes exist, which may account for their ability to cause frequent disease. Cytomegalovirus causes cytomegalic inclusion disease (CID), especially congenital abnormalities, in neonates. Malformations include microencephaly. Seizures, deafness, jaundice, and purpura can also occur. CID is also one of the leading causes of mental retardation in the United States. Respiratory syncytial virus (RSV) is the leading cause of pneumonia and bronchiolitis in infants. Viremia does not occur and treatment in several ill infants is aerosolized ribavirin. Orchitis, a complication of mumps virus infection in post pubertal males, can cause sterility if bilateral.