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Rubellavirus
GENERAL CONCEPTS:
- Rubella virus is a member of the Togaviridae family and produces the disease commonly known as German measles.
- Prior to the introduction of the vaccine, rubella was a common, mild disease with a rash. It was found worldwide and mostly affected children. It was uncommon in adults but had severe manifestations when affecting a pregnant woman during the first trimester because of the potential for birth defects.
DISTINCTIVE PROPERTIES:
- The structure of Rubellavirus is similar to other Togaviruses.
- Humans are the only known reservoir for disease.
PATHOGENESIS:
- Transmission of the virus is via the respiratory route.
- Initial multiplication occurs in the respiratory tract. One week after infection, viremia occurs and this is later followed by the skin rash. The highest concentration of virus in the respiratory tract begins 3 days prior to the rash and lasts until 3 days after.
- If the virus infects a woman during the first 3-4 months of pregnancy, it may infect the placenta or fetus, multiply in any fetal organ and cause damage or death of certain cell types. This congenital rubella syndrome affects the eyes, heart and brain. The virus may persist in the child's tissues for 3-4 years and be shed for up to a year after birth.
HOST DEFENSES:
- Humoral defenses soon after the viremia help to clear the virus from the blood and prevent continued spread. Cell-mediated defenses clear the virus from tissues. The immune responses generated by natural infections provide life-long immunity.
EPIDEMIOLOGY:
- Before the vaccine, sporadic outbreaks and epidemics occurred every 6-9 years following a seasonal pattern (late winter, early spring, typical for respiratory disease).
- An epidemic in 1964-65 in the US produced 12.5 million cases of disease and resulted in 20,000 cases of congenital rubella syndrome.
DIAGNOSIS:
- Clinical: Following a 14-20 day incubation period (the "prodrome"), a rash develops on the face and neck and then the trunk and extremities. Lymph nodes become enlarged about a week before the rash and persist for 1-2 weeks after. Congenital rubella symptoms vary depending on the organs affected but typically the eyes, ears, heart and brain are involved. Confirmation of disease is critical in pregnant women.
- Laboratory: Illustrating a 4-fold increase in serum titer against Rubellavirus is diagnostic.
CONTROL:
- Sanitary: Avoidance of contacts.
- Immunological: A live vaccine is given in combination with measles and mumps (MMR) to all children over 15 months and selective young and adult women NOT pregnant or 3 months prior to becoming pregnant. Since its introduction in the late 1960's, the vaccine has greatly reduced the incidence of disease.
- Chemotherapeutic: None available.
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