Rubella is a contagious virus that causes a mild illness in most people but can severely harm an unborn baby if a pregnant person becomes infected. Often called German measles, it spreads through respiratory droplets and produces a distinctive rash lasting about three days. Thanks to widespread vaccination, rubella has been eliminated in much of the world, though it still circulates in regions with lower vaccine coverage.
How Rubella Spreads
Rubella travels from person to person through tiny droplets released when someone coughs or sneezes. After exposure, the virus has an average incubation period of 17 days, though it can range from 12 to 23 days. During this time, the virus multiplies in the respiratory tract and enters the bloodstream, a phase called viremia. An infected person can spread the virus to others from about a week before the rash appears to roughly a week after, meaning many people transmit it before they even know they’re sick.
Symptoms in Children and Adults
Rubella typically starts with one to five days of low-grade fever, general fatigue, and mild upper respiratory symptoms like a stuffy nose. Swollen lymph nodes are one of the earliest and most telling signs, particularly the nodes behind the ears and at the base of the skull. These swollen glands often appear before the rash and can persist for several weeks.
The rash itself is mild and made up of small, flat or slightly raised pink spots. It begins on the face and moves downward over the trunk and limbs, usually appearing 14 to 17 days after exposure. Unlike the measles rash, which lasts five to six days and can be quite intense, rubella’s rash fades within about three days. Some people also develop Forchheimer spots, tiny reddish dots on the soft palate inside the mouth, either just before or alongside the rash.
Up to half of rubella infections produce no noticeable symptoms at all, which is one reason the virus can spread so easily through a community before anyone realizes it’s circulating.
Complications in Adults
While rubella is usually mild in children, adults tend to have a rougher experience. Joint pain and swelling affect up to 70% of women who contract rubella, typically hitting the fingers, wrists, and knees. These joint symptoms can last for weeks but almost always resolve completely. Encephalitis, or inflammation of the brain, is rare but does occur in roughly 1 in 6,000 cases, and it affects adult women more often than men or children. Conjunctivitis is another possible complication, particularly during pregnancy.
How Rubella Differs From Measles
The names “German measles” and “regular measles” cause a lot of confusion, but rubella and measles (rubeola) are caused by entirely different viruses and produce distinctly different illnesses. Measles hits much harder: it begins with 10 to 12 days of incubation followed by two to three days of high fever, cough, red eyes, and runny nose. Before the measles rash appears, white spots called Koplik’s spots show up inside the cheeks, a sign unique to measles. The measles rash is more intense, lasts five to six days, and the illness overall is significantly more severe.
Rubella’s prodrome is milder, the fever is lower, and the rash is lighter and shorter-lived. The hallmark of rubella is swollen lymph nodes behind the ears, which isn’t typical of measles. Both rashes start on the face and spread downward, which adds to the confusion, but the severity and duration are quite different.
Congenital Rubella Syndrome
The greatest danger of rubella is to a developing fetus. When a pregnant person contracts rubella, the virus can cross the placenta during the viremia phase, roughly five to seven days after exposure. The consequences depend heavily on timing. Infection during the first 12 weeks of pregnancy causes birth defects in up to 85% of cases. Between weeks 13 and 16, that number drops to around 50%. During the latter half of the second trimester, it falls to about 25%. After 20 weeks, the risk decreases substantially.
The birth defects grouped under congenital rubella syndrome (CRS) are serious and often permanent. The classic pattern involves three systems: the heart, the eyes, and the ears. Heart defects include holes between heart chambers and problems with blood vessels near the heart. Eye problems range from cataracts to abnormally small eyes. Sensorineural hearing loss, the most common single defect, results from damage to the inner ear and is often profound and permanent. Many children with CRS have involvement in more than one of these areas.
How Rubella Is Diagnosed
Because rubella’s symptoms overlap with many other viral illnesses, a clinical diagnosis based on symptoms alone isn’t reliable. Confirmation requires a blood test. The standard approach looks for rubella-specific IgM antibodies, which the immune system produces in response to a new infection. These antibodies are detectable between 4 and 30 days after the rash appears, but timing matters: on the day the rash first shows up, only about 50% of infected people will test positive. By day five, that rises above 90%. If a blood sample taken in the first few days comes back negative, a second sample is needed to rule rubella out.
For cases where the timing of infection is unclear, particularly in pregnant patients, doctors can measure how tightly IgG antibodies bind to the virus, a property called avidity. Loosely binding (low-avidity) antibodies suggest a recent infection within the past four months, while tightly binding antibodies indicate an older, more distant exposure. Genetic testing on throat or nasal swabs can also detect rubella, but the window is narrow: the virus is only detectable in respiratory samples from about two days before to four days after the rash starts.
For checking immunity rather than diagnosing active infection, a blood level of IgG antibodies above 10 IU/ml is the standard cutoff used in the United States.
Vaccination and Prevention
A single dose of the rubella vaccine, given as part of the MMR (measles, mumps, and rubella) combination, is about 97% effective at preventing rubella. The standard schedule calls for two doses: the first at 12 to 15 months of age and the second at 4 to 6 years. The second dose primarily boosts measles and mumps protection, since one rubella dose already provides near-complete immunity for the vast majority of people.
Vaccination has been remarkably successful. Across the WHO European Region, nearly every country has achieved verified elimination of endemic rubella as of 2023, with only a small number still undergoing review. The Americas declared rubella eliminated in 2015. However, the virus continues to circulate in parts of Africa, Southeast Asia, and the Western Pacific where vaccine coverage remains inconsistent, and travel-related cases still occur in countries that have otherwise eliminated the disease.
The Virus Itself
Rubella is the sole member of the genus Rubivirus within the Matonaviridae family. It’s a single-stranded, positive-sense RNA virus, meaning its genetic material can be directly read by the cell’s machinery to produce viral proteins. The virus particle is wrapped in a lipid envelope studded with two surface proteins, E1 and E2, that form pairs and help the virus attach to and enter human cells. Its shape is somewhat irregular (described as pleomorphic), and it’s relatively fragile outside the body, easily destroyed by heat, UV light, and common disinfectants.
Unlike many other RNA viruses, rubella has only one known serotype. This is a major reason why a single vaccine dose works so well: there’s only one version of the virus the immune system needs to recognize.