Abstract
Rubella is an acute viral illness with characteristic maculopapular rash and low-grade fever.
Up to 50 per cent of cases may pass unnoticed without any symptoms. The disease occurs more commonly in young children.
The most devastating consequence occurs when rubella infects a pregnant female early during the period of embryogenesis, with serious multiple birth defects, known as congenital rubella syndrome (CRS).
Introduction
Rubella is an acute viral illness with characteristic maculopapular rash and low-grade fever.
Up to 50 per cent of cases may pass unnoticed without any symptoms. The disease occurs more commonly in young children.
The most devastating consequence occurs when rubella infects a pregnant female early during the period of embryogenesis, with serious multiple birth defects, known as congenital rubella syndrome (CRS).
Microbiology and Transmission/Epidemiology
Rubella virus is an enveloped positive-stranded RNA virus, belonging to the Togaviridae family.1
The virus is directly transmitted by direct or droplet contact from nasopharyngeal secretions.2
The virus replicates in the respiratory mucosa and cervical lymph nodes, before reaching the target organs via systemic circulation.
The average incubation period is 17 days (range: 12–23 days).
Rubella is most infectious when the rash is erupting; however, the infectious period extends from seven days before to seven days after rash onset.
Maternal viraemia may occur five to seven days after exposure, when the virus spreads throughout the body, with transplacental transfer and infection of the fetus also occurring.
Before the availability of rubella vaccines, rubella was a common disease occurring primarily among young children.
Incidence was highest during the spring, with epidemics every six to nine years.
Clinical Picture3
2. Mild, maculopapular rash
The rash occurs in 50–80 per cent of cases, characteristically starting on the face, then becoming generalised within 24 hours, and lasting for about three days.
Lymphadenopathy may precede rash, and often involves posterior auricular or suboccipital lymph nodes, but can be generalised, and lasts from five to eight days.
Adults, more commonly women, may develop arthritis/arthralgia that usually lasts 3–10 days.4
5. Thrombocytopenia is a rare sign
6. Neurological disorders are also a rare occurrence
7. About 25–50 per cent of infections are asymptomatic
The following case definition for rubella was approved by the Council of State and Territorial Epidemiologists (CSTE) in 2012:
Suspected: Any generalized rash illness of acute onset that does not meet the criteria for probable or confirmed rubella or any other illness.
Probable: In the absence of a more likely diagnosis, an illness characterized by all of the following:
acute onset of generalized maculopapular rash; and
temperature greater than 99.0°F or 37.2°C, if measured; and
arthralgia, arthritis, lymphadenopathy, or conjunctivitis; and
lack of epidemiologic linkage to a laboratory-confirmed case of rubella; and
Non-contributory or no serologic or virologic testing.
Confirmed: A case with or without symptoms who has laboratory evidence of rubella infection confirmed by one or more of the following:
isolation of rubella virus; or
detection of rubella-virus specific nucleic acid by reverse transcriptase–polymerase chain reaction (RT-PCR); or
significant rise between acute- and convalescent-phase titres in serum rubella IgG antibody level by any standard serologic assay; or
positive serologic test for rubella IgM antibody (not explained by MMR vaccination during the previous 6–45 days, and not otherwise ruled out by more specific testing in a public health laboratory)
OR
An illness characterized by all of the following:
Acute onset of generalized maculopapular rash; and
Temperature greater than 99.0°F or 37.2°C; and
Arthralgia, arthritis, lymphadenopathy, or conjunctivitis; and
Epidemiologic linkage to a laboratory-confirmed case of rubella.’
Diagnosis of Maternal Infection5
ELISA Serologic Testing
Enzyme-linked immunoassay (ELISA) serologic testing for IgM/IgG antibodies is the mainstay of laboratory diagnosis.
It is best carried out within 7–10 days after the onset of the rash or a history of exposure and should be repeated two to three weeks later.
IgM
Rubella virus immunoglobulin M (RV‐IgM) appears within three days after the rash and generally disappear in 4–12 weeks.
IgG
Rubella virus immunoglobulin G (RV‐IgG) detected by ELISA appear slightly later (five to eight days after the onset of the rash) and persists throughout life.
RV‐IgG reaches a steady state at any time from a few days to a few weeks.
The maximal and residual RV‐IgG rates are extremely variable, depending on the patient tested and the assay used.
A high RV‐IgG titre is not necessarily a marker of a recent primary infection.
The Presence of a Rubella Infection is Confirmed By:
1. A positive serologic test for rubella-specific IgM, which indicates recent infection
2. A four-fold rise in rubella IgG antibody titre between acute and convalescent serum specimens, which also indicates recent infection
3. High IgG titres (10 IU/mL or greater) indicate old infection and probable immunity
4. A high IgG avidity index indicates old infection and possible immunity
Isolation of rubella virus in nasopharyngeal secretions by RT-PCR.
Complications
1. Arthralgia or arthritis may complicate up to 70 per cent of adult women with rubella
2. Thrombocytopenic purpura
3. Encephalitis
4. Guillain–Barré syndrome (a disorder in which the body’s immune system attacks part of the peripheral nervous system). Symptoms include varying degrees of weakness or tingling sensations in the legs. Symmetrical weakness and abnormal sensations spreading to the arms and upper body may occur in rare cases
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