The disease is caused by rubella virus, a togavirus that is enveloped and has a single-stranded RNA genome.[19] The virus is transmitted by the respiratory route and replicates in the nasopharynx and lymph nodes. The virus is found in the blood 5 to 7 days after infection and spreads throughout the body. The virus has teratogenic properties and is capable of crossing the placenta and infecting the fetus where it stops cells from developing or destroys them.[10] During this incubation period, the patient is contagious typically for about one week before he/she develops a rash and for about one week thereafter.
Increased susceptibility to infection might be inherited as there is some indication that HLA-A1 or factors surrounding A1 on extended haplotypes are involved in virus infection or non-resolution of the disease.[20] [21]
Rubella virus specific IgM antibodies are present in people recently infected by rubella virus, but these antibodies can persist for over a year, and a positive test result needs to be interpreted with caution.[22] The presence of these antibodies along with, or a short time after, the characteristic rash confirms the diagnosis.[23]
Rubella has symptoms that are similar to those of flu. However, the primary symptom of rubella virus infection is the appearance of a rash (exanthem) on the face which spreads to the trunk and limbs and usually fades after three days (that is why it is often referred to as three-day measles). The facial rash usually clears as it spreads to other parts of the body. Other symptoms include low grade fever, swollen glands (sub-occipital and posterior cervical lymphadenopathy), joint pains, headache, and conjunctivitis.[10]
The swollen glands or lymph nodes can persist for up to a week and the fever rarely rises above 38 °C (100.4 °F). The rash of German measles is typically pink or light red. The rash causes itching and often lasts for about three days. The rash disappears after a few days with no staining or peeling of the skin. When the rash clears up, the skin might shed in very small flakes where the rash covered it. Forchheimer's sign occurs in 20% of cases, and is characterized by small, red papules on the area of the soft palate.[11]
Rubella can affect anyone of any age and is generally a mild disease, rare in infants or those over the age of 40. The older the person is the more severe the symptoms are likely to be. Up to 60% of older girls or women experience joint pain or arthritic type symptoms with rubella.[12]
In children rubella normally causes symptoms which last two days and include:[13]
Rash beginning on the face which spreads to the rest of the body.&Low fever of less than 38.3 °C (101 °F).&Posterior cervical lymphadenopathy.[14
In older children and adults additional symptoms may be present including:[13]
Swollen glands&Coryza (cold-like symptoms)&Aching joints (especially in young women
Rare problems can occur including the following:
Brain inflammation&Ear infection [15
Coryza in rubella may convert to pneumonia, either direct viral pneumonia or secondary bacterial pneumonia, and bronchitis (either viral bronchitis or secondary bacterial bronchitis).[16]
Rubella can cause congenital rubella syndrome in the newborn. The syndrome (CRS) follows intrauterine infection by the rubella virus and comprises cardiac, cerebral, ophthalmic and auditory defects.[17] It may also cause prematurity, low birth weight, and neonatal thrombocytopenia, anemia and hepatitis. The risk of major defects or organogenesis is highest for infection in the first trimester. CRS is the main reason a vaccine for rubella was developed.[18]
Many mothers who contract rubella within the first critical trimester either have a miscarriage or a stillborn baby. If the fetus survives the infection, it can be born with severe heart disorders (patent ductus arteriosus being the most common), blindness, deafness, or other life-threatening organ disorders. The skin manifestations are called "blueberry muffin lesions".[18] For these reasons, rubella is included on the TORCH complex of perinatal infections.
About 100,000 cases of this condition occur each year.[3]