The virus, which is spread in droplets shed in respiratory secretions, infects the respiratory tract and then the bloodstream.
Its incubation period is 18 days on average.
Postnatally Acquired Rubella Infection: is acquired after birth and usually results in an extremely mild or subclinical illness.
The foremost symptoms of postnatally acquired rubella include posterior auricular, cervical, and suboccipital lymphadenopathy; fever; and rash. The rash often begins on the face and spreads down the body (centrifugal).
Rash is composed of similar lesions that do not coalesce. It is maculopapular but not confluent, is sometimes accompanied by mild coryza and conjunctivitis, and generally lasts for 3 to 5 days. A petechial enanthem on the soft palate, designated Forschheimer spots, may occur but is not specific for rubella.
Congenital Rubella: Maternal infection in early pregnancy can lead to fetal infection, with resultant congenital rubella. The classic signs of congenital rubella are cataract, mental retardation, heart disease, and deafness, but a myriad of other defects have been reported.
Maternal infection during the first trimester leads to fetal infection in about 50% of cases; maternal infection early in the second trimester leads to fetal infection in about one-third of cases. Fetal malformations not only are more common after maternal infection in the first trimester but also tend to be more severe and to involve more organ systems. While a fetus infected in the fourth week of gestation may develop many problems, one infected later (e.g., in the 20th week) may have isolated deafness as the only symptom.
A laboratory diagnosis is more often made serologically. Acute rubella is diagnosed by the documentation of a fourfold or greater rise in the titer of IgG antibodies in paired acute- and convalescent-phase serum specimens or by the detection of rubella-specific IgM antibodies in one serum specimen.
The isolation of rubella virus in cell cultures of throat samples, urine, or other secretions is difficult and expensive but is sometimes undertaken.
There is no specific therapy for rubella. At one time, immune globulin was used in an effort to prevent congenital rubella when pregnant women became infected. However, since administration of immune globulin did not prevent maternal viremia, this approach was discarded. Treatment is given for symptoms such as fever, arthralgia, and arthritis.
Live attenuated rubella vaccine was licensed in 1969, 7 years after the virus was first isolated in culture.
The present vaccination strategy, developed in part when measles was not being adequately controlled, is to immunize all infants at 12 to 15 months of age with measles-mumps-rubella (MMR) vaccine and to administer a second dose at 4 to 12 years of age. Rubella vaccine may also be administered to anyone who is thought to be susceptible to the infection and is not pregnant.