What is Rubella?
Also Known As:
German Measles Three-day Measles 3-day Measles
Rubella Antibodies IgM and IgG
Rubella is a virus that causes an infection that is usually mild and characterized by fever and rash that last about 2 to 3 days. The Infection is highly contagious but is preventable with a vaccine. A rubella test detects and measures rubella antibodies in the blood that are produced by the body’s immune system in response to immunization or an infection by the rubella virus.
Clinical diagnosis of rubella is unreliable; therefore, cases must be laboratory-confirmed. Antibody tests are the most common methods of confirming the diagnosis of rubella.
The rubella virus generally causes a mild infection marked by a fine red rash that appears on the face and neck and then travels to the trunk and limbs before disappearing a few days later. The virus is spread by contact with an infected person through coughing and sneezing. The infection can cause symptoms such as fever, enlarged lymph nodes, runny nose, red eyes, and joint pain. Symptoms may be so minimal, especially in children, that they go unnoticed and people do not know that they have a viral illness. In most people, rubella goes away within a couple of days without any special medical treatment and usually causes no further health issues.
The primary concern with rubella infection is when a pregnant woman contracts it for the first time during the first three months of her pregnancy. The developing baby (fetus) is most vulnerable to the virus at this time. If rubella is passed from a mother to her unborn baby, it can cause miscarriage, stillbirth, or congenital rubella syndrome (CRS), a group of serious birth defects that will permanently affect the child. CRS can cause intellectual and developmental disabilities, deafness, cloudiness of the lens of the eyes (cataracts), an abnormally small head, liver problems, and heart defects.
Because of the severe consequences for unborn babies, a national campaign was started in 1969 to immunize all children in the United States and to work to eradicate rubella infection, first in the U.S. and then throughout the world. The rubella vaccine is contained in a combination vaccine called MMR, which stands for measles, mumps and rubella. All children should receive two doses of MMR, the first dose at 12-15 months of age and the second dose at 4-6 years of age.
Prior to 1969 and routine vaccinations, rubella infections would emerge as cyclic outbreaks that lasted for several years. According to the Centers for Disease Control and Prevention (CDC), during the 1962-1965 rubella epidemic, 12.5 million cases of rubella occurred in the U.S. and there were 20,000 infants born with CRS. Due to vaccination efforts, these numbers have decreased drastically. The number of reported cases of rubella in the United States has declined dramatically to a median of 11 cases annually in 2005-2011.
The CDC now declares endemic rubella to be eradicated in the U.S., although people traveling from other countries bring it to the U.S. and the incidence continues to be monitored. People should not become complacent with this reduction, however, and the CDC cautions people to continue to have their children vaccinated. Anyone who has not received the vaccination as a child (and a few that have) may still be vulnerable to rubella infection.
Pregnant women and women considering pregnancy continue to be routinely tested for rubella antibodies to ensure that they are immune.
How is the sample collected for testing?
A blood sample is drawn from a vein in the arm of an adult or from a heel prick or the umbilical cord of a newborn.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
The rubella test is used to detect antibodies in the blood that develop in response to a rubella infection or immunization. Rubella testing may be used to:
- Confirm the presence of adequate protection against the rubella virus (immunity)
- Detect a recent or past infection
- Identify those who have never been exposed to the virus and those who have not been vaccinated
- Verify that all pregnant women and those planning to become pregnant have a sufficient amount (titer) of rubella antibodies to protect them from infection
Rubella is a viral infection that is usually mild and marked by fever and rash that last about 2 to 3 days. The infection usually resolves without treatment. However, if a pregnant woman contracts it for the first time during the first three months of her pregnancy, rubella can cause serious complications in the developing baby (fetus). (For more on this, read the “What is being tested?” section.)
A rubella test may be ordered for a person, pregnant or not, who has symptoms that a health practitioner suspects are due to a rubella infection. It may also be ordered for a newborn who is suspected to have become infected during pregnancy or that presents with congenital birth defects that a health practitioner suspects may be due to a rubella infection.
There are two types of rubella antibodies that lab tests can detect, IgM and IgG:
- The first type to appear in the blood after exposure is the IgM rubella antibody. The level of this protein rises and peaks in the blood within about 7 to 10 days after infection and then tapers off over the next few weeks, except in an infected newborn, in whom it may be detected for several months to a year.
- The IgG rubella antibody takes a bit longer to appear than the IgM, but once it does, it stays in the bloodstream for life, providing protection against re-infection. The presence of IgM rubella antibodies in the blood indicates a recent infection while the presence of IgG antibodies may indicate a recent or past rubella infection, or indicate that a rubella vaccine (the measles, mumps, rubella vaccine) has been given and is providing adequate protection.
The IgM rubella test is the standard test for the rapid laboratory diagnosis of rubella. Detection of a rise in IgG rubella in blood samples collected when a person is acutely ill and then as the person begins to recover (convalescent phase) can be used to confirm infection. The antibody tests vary among laboratories and the state health department can provide guidance on available laboratory services and preferred tests.