Rubella, also known as German measles or "three-day measles," is a contagious viral infection that brings on a rash as well as other symptoms. But many children have such mild symptoms that they're unaware of being infected. It's milder than measles and doesn't last as long.

Rubella is a significant health risk for pregnant women. If a pregnant woman is infected with rubella, especially in the first trimester (1 to 3 months), she may miscarry or the fetus may suffer severe birth defects.

After a bout with rubella, a person has lifelong immunity. The disease used to be common, with epidemics sweeping across North America every 6 to 9 years. Major epidemics occurred at a frequency of every 30 years, with the last one recorded in 1964, affecting over 12 million people in the US.

The virus was first isolated in the laboratory in 1962 and a vaccine was made available in 1969. Since then, the measles-mumps-rubella (MMR) vaccine has cut the frequency of the disease dramatically in countries that include the vaccine in their immunization programs.

Rubella is caused by a virus. It is spread in the same way as any viral cold - by tiny droplets produced from the nose and mouth. It's not as contagious as a cold or the measles, but it has a long incubation period (the time between getting infected with the virus and getting sick) that varies from 12 to 23 days. People who get the virus are infectious (can spread it to others) for up to 10 days before symptoms appear. People are most contagious a few days before the rash appears until 7 days after its onset.

Because rubella is rarer these days, an increasing number of adults have never been infected with the disease and therefore aren't immune unless they have been vaccinated.

Because many people with rubella have mild symptoms, it can be difficult to diagnose. Your doctor will perform a physical exam and ask you about your symptoms. Rubella will likely be suspected if you have a rash and swollen lymph nodes when you see your doctor. If your doctor suspects rubella, they may order blood tests.

One particular blood test looks for antibodies against rubella, but there are some limitations with this test. Unfortunately, it may miss low-level infections.

As with the measles and most other viral illnesses, there's no cure for rubella. You can only wait for it to go away. Analgesics such as acetaminophen* and ibuprofen can control fever and headache, but children should not be given ASA (acetylsalicylic acid), which may cause Reye's syndrome (a serious disease that can occur if a child with a viral infection is given ASA; Reye’s syndrome affects many organs, particularly the liver and brain).

For couples planning families, both partners should be vaccinated if they haven't done so already. A person is fully immune one month after inoculation. Women of childbearing age are routinely given a blood test to determine if they're immune.

Once a woman's pregnant, it's too late for her to be vaccinated, as the vaccine contains a live (though weakened) virus that could harm the baby. In fact, women should not be vaccinated 28 days before they conceive.

The vaccine protects more than 95% or people who receive it and protection lasts for life. It is important to be vaccinated if you've never had the disease. Rubella symptoms tend to be more severe in adults than in children, so it's worth a shot to avoid it.

Travellers to areas with a high incidence of rubella should see their doctor at least 6 to 8 weeks before they depart to be sure their rubella immunization is up-to-date.