Infectious Disease and Microbiology – Rubella (German Measles)

Rubella, also called German measles, is a contagious viral infection caused by an enveloped RNA virus belonging to the togavirus family. In most children and adults the illness is mild, but infection during pregnancy can have devastating effects on the developing fetus.

Rubella has become uncommon in countries with widespread vaccination. Historically, the incidence in the United States fell to approximately 1 case per 100,000 population, with most cases occurring among unvaccinated individuals or people arriving from areas where vaccination coverage is lower. Worldwide incidence has also declined substantially following expansion of immunization programs.

The most important risk factor for rubella is lack of vaccination. Before widespread immunization, the disease occurred predominantly in children between 5 and 14 years of age. In areas where vaccination coverage remains inadequate, infection may also occur frequently among adolescents and young adults.

Prevention depends primarily on vaccination with the live attenuated rubella vaccine, usually administered as part of the measles-mumps-rubella vaccine. Routine childhood immunization includes two doses, traditionally given around 12–15 months of age and again between 4 and 6 years.

Women of childbearing age should have their rubella immune status assessed when appropriate, particularly before pregnancy or during early prenatal care. A nonimmune woman should be vaccinated after delivery rather than during pregnancy because the vaccine contains live attenuated virus. Pregnancy should be avoided for approximately 28 days following vaccination.

If rubella vaccine is inadvertently administered during pregnancy, counseling is appropriate, but vaccination alone is not considered an automatic indication for pregnancy termination. Immunocompromised individuals receiving significant chemotherapy or undergoing bone marrow transplantation generally should not receive live rubella vaccine.

Patients with confirmed rubella should avoid close contact with susceptible individuals and should generally remain isolated for approximately one week after the rash appears. Immunoglobulin has not been considered a reliable method of preventing fetal infection in a susceptible pregnant woman after exposure.

Rubella has an incubation period of approximately 2–3 weeks. Transmission occurs primarily through respiratory droplets and secretions from the upper respiratory tract.

The infection is generally mild in children and adults but is especially important during pregnancy. Maternal infection during the first trimester and early second trimester carries the greatest risk of congenital rubella syndrome. Maternal infection may be mild or even asymptomatic while still causing significant fetal injury.

Infants with congenital rubella may continue shedding virus for many months and, in some cases, for as long as 1–2 years after birth. They can therefore remain infectious for prolonged periods.

Rubella commonly begins with a mild upper respiratory illness characterized by low-grade fever, malaise, and coryza. Some patients may have few or no symptoms before the rash develops.

Physical examination may reveal small red lesions on the soft palate followed by a fine maculopapular or morbilliform rash. The rash usually begins on the face, often around the postauricular region, and spreads downward across the trunk and extremities over the next 1–2 days. The lesions may merge and can occasionally be pruritic.

Tender postauricular and occipital lymphadenopathy is a characteristic early finding. Conjunctivitis may also occur. Adolescents and adults, particularly women, may develop arthralgia or arthritis after the rash, which can persist for several days or occasionally longer.

Congenital rubella syndrome can affect multiple organ systems. Manifestations include fetal death, growth restriction, developmental delay, sensorineural deafness, cataracts, retinopathy, patent ductus arteriosus, pulmonary artery abnormalities, hepatosplenomegaly, diabetes mellitus, and thyroid disorders. Some abnormalities may not become apparent until later childhood.

Laboratory testing may show leukopenia and atypical lymphocytes, although these findings are nonspecific. Serologic testing is commonly used to confirm infection.

Rubella-specific IgM antibodies generally become detectable within several days of illness and may remain present for several weeks. However, false-positive IgM results may occur because of infections such as measles, cytomegalovirus, Epstein-Barr virus, or parvovirus B19, as well as interference from rheumatoid factor.

Rubella IgG testing can demonstrate prior immunity, while IgG avidity testing may help distinguish recent primary infection from past infection or reinfection. When a diagnosis has major implications, particularly during pregnancy, positive serologic findings should be confirmed with additional testing when available.

Polymerase chain reaction testing can detect rubella viral RNA in respiratory secretions, blood, amniotic fluid, or fetal specimens. PCR of oral or nasopharyngeal samples is most useful during the early period after rash onset. Viral culture is available only in specialized laboratories.

The differential diagnosis includes measles, parvovirus B19 infection, enterovirus infection, HIV-associated rash, scarlet fever, and medication-related eruptions.

There is no specific antiviral treatment for uncomplicated rubella or congenital rubella syndrome. Management of acquired rubella is supportive, with rest, adequate hydration, and symptomatic treatment when necessary.

Children with congenital rubella syndrome require long-term multidisciplinary follow-up because hearing impairment, visual abnormalities, developmental problems, endocrine disorders, and cardiovascular defects may require ongoing treatment.

The prognosis of uncomplicated rubella in children and adults is excellent, with most patients recovering completely. Congenital rubella syndrome, however, may cause lifelong disability and significant multisystem disease.

The most important complication is congenital rubella syndrome following maternal infection during pregnancy. Sensorineural hearing loss is among the most frequent permanent manifestations. Other uncommon complications of acquired rubella include thrombocytopenia and acute disseminated encephalomyelitis.