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 passed through nasal and throat secretions and 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 are not perceived as being from a viral illness. In most patients, rubella goes away within a couple of days without any special medical treatment and 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 fetus is the most vulnerable to the virus at this time and, if it is passed on to the fetus by the mother, it can cause miscarriage, stillbirth, and/or congenital rubella syndrome (CRS), a group of serious birth defects that will permanently affect the child. CRS can cause delayed development, mental retardation, deafness, cataracts, an abnormally small head, liver problems, and heart defects.
Because of the severe consequences for developing fetuses, 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. Prior to this time, 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 United States and there were 20,000 infants that were born with CRS. Due to vaccination efforts, these numbers have decreased drastically. In 2006, there were only 11 cases of rubella recorded in the United States and about half of the cases occurred in people who were born outside the U.S. (in countries without widespread vaccination programs). Each year since 2001, there have been fewer than 25 cases reported. The CDC now declares endemic rubella to be eradicated in the U.S., although 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.
How is the sample collected for testing?A blood sample is drawn from a vein in the arm of an adult or from a heelprick 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:
- confirm the presence of adequate protection against the rubella virus
- 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
Both the IgM and IgG antibody tests may be ordered on a person, pregnant or not, who has symptoms that the doctor suspects are due to a rubella infection. They may also be ordered on a newborn that is suspected to have become infected during pregnancy or that presents with congenital birth defects that the doctor suspects may be due to a rubella infection.
When is it ordered?
The IgG rubella test is ordered when you are pregnant, planning on becoming pregnant, or whenever a check of immunity against rubella is required. IgM and IgG rubella tests are ordered when a pregnant woman has a fever and rash and/or other symptoms that may indicate a rubella infection. Since many conditions can cause similar symptoms, the doctor will need to order the tests in order to confirm the diagnosis.
IgM and IgG tests may be ordered on a newborn when the mother was diagnosed with a rubella infection during pregnancy and/or when a newborn is born with birth defects (hearing loss, cardiovascular abnormalities, cataracts, central nervous system disease) that could be due to CRS.
Since IgM and IgG rubella antibodies take some time to appear after infection, the tests may be repeated in 2 to 3 weeks to see if the antibody levels have become detectible (when initially absent) and to determine whether the levels are rising or falling over time.
This test may be required of a health care worker or a person starting college and is still ordered on women in some states as part of the blood testing required to obtain a marriage license.
What does the test result mean?
In an adult or child, the absence of IgG rubella antibodies means that the person likely has not been exposed to the rubella virus or been vaccinated and is not protected against it. The presence of IgG antibodies but not IgM antibodies indicates a history of past exposure to the virus or vaccination and indicates that the person tested should be immune to the rubella virus. The presence of IgG antibodies, but not IgM antibodies, in a newborn means that the mother’s IgG antibodies have passed to the baby in utero and these antibodies may protect the infant from rubella infection during the initial six months of life. The presence of IgM antibodies in a newborn indicates that the baby was infected during pregnancy (because the mother’s IgM antibodies do not pass to the baby through the umbilical cord). The presence of IgM antibodies, with or without IgG antibodies, in a child or adult indicates a recent infection with the rubella virus.
age Igm igg interpretation Adult/Child + +/- Recent infection Adult/Child + Prior infection, immune Newborn + In utero infection Newborn + Maternal immunities, passive immunity for up to six months
Occasionally, a patient will have a false positive test for IgM rubella antibodies because the test components cross react with other proteins in their body. To confirm the IgM result, the doctor may order an IgG test to establish a baseline level of antibody and may repeat the IgG test again in 2-3 weeks to look for a significant increase in the amount (titer) present, indicating a recent rubella infection.
Is there anything else I should know?
It is possible to test for the genetic material (RNA) of the virus directly in a sample or culture a body fluid sample, such as a throat swab, for the rubella virus. The rubella virus takes at least a week or more to be detected in culture, and special molecular assays or specifically prepared antibodies must be used to determine if the virus is present. This may occasionally be done to help a doctor diagnose rubella infection in a newborn. Because this procedure is complex and expensive, most diagnostic laboratories refer this testing to a reference lab such as the Centers for Disease Control and Prevention (CDC). The number of cases of rubella and congenital rubella is monitored by the CDC to track the effectiveness of the rubella vaccine and to detect any outbreaks of the disease.
Should pregnant women be vaccinated for rubella?
Does the vaccine have any risks?The vaccine contains a live virus that has been altered so it promotes an antibody response but does not cause a rubella infection. Some people may have a rash that lasts 2–3 weeks after vaccination and pain in their joints, especially their hands and wrists. Side effects are rarely seen in young children who get the vaccine. Patients who have suppressed immune systems, such as those with HIV/AIDS and cancer patients undergoing chemotherapy, should consult with their doctors before getting a rubella vaccine.
How soon after I have been exposed to the virus will I get it?If you are going to have symptoms, the rash usually begins 15–17 days after coming in contact with an infectious person, but it may take as long as 3 weeks. A person is usually infectious about a week before the rash is visible and for 1-2 weeks afterwards. A newborn who was infected during pregnancy may remain infectious for several months.
What do the letters in the MMR vaccine stand for?Measles, Mumps, and Rubella. Since all three of these are common viral illnesses, they are contained within one vaccine. Measles is also known as Rubeola and is different from Rubella (German Measles).