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NAME OF DISEASE: Rubella
German measles
Three-day measles
ETIOLOGICAL AGENT:
The rubella virus (a togavirus), contains RNA and an envelope. It replicates in the cytoplasm.
EPIDEMIOLOGY:
Man is only host. Disease is spread by droplet inhalation. Attack rate is highest in five-nine year age group but is also high in older children and adolescents and in adults up to 35 years of age.
PATHOLOGY:
Incubation period is 18 days. The virus initially replicates in the upper respiratory tract mucosa and in cervical lymph nodes. After multiplication at these sites, the virus is disseminated to other parts of the body through the blood. Viremia can be detected as early as 9 days before the exanthem. During this period or shortly thereafter, enlargement of the cervical lymph nodes commonly appears. Coincident with development of the rash, or within 24-48 hours, neutralizing antibodies become detectable and circulating virus disappears from the blood. The exanthem represents an inflammatory effect exerted by an antibody-virus complex, rather than direct viral invasion of the vascular epithelium. Since the disease is mild, few histological studies have been done; nonspecific acute and chronic inflammatory changes have been described in the skin and affected lymph nodes.
COMPLICATIONS:
1. Encephalitis (1/6000 cases).
More common in children. Occurs one-seven days after rash.
CSF may contain up to 300 cells, mostly monocytes. Sugar and protein normal.
EEG
abnormalities may persist for months or years.
2. Arthritis (33% of adult
women). Appears with rash or within three days of it, most
frequently involving the fingers, wrists and knees. Tests for rheumatoid
factor may be
positive. Lasts 2-30 days. Self limited.
3. Hemorrhagic manifestations
(rare). Begins abruptly three-four days after onset of the rash.
The skin and the mucous membranes are the most common sites of bleeding.
DIAGNOSIS:
The clinical diagnosis of rubella may be made with assurance only in typical cases occurring during an epidemic. The large number of atypical and subclinical cases of rubella, together with the numerous conditions of an infectious or allergic nature that may be associated with a rubelliform rash, make the clinical diagnosis difficult. The stages of the disease are:
1. Incubation period (18
days). Virus is replicating in mucosa and lymph nodes and viremia
occurs. Lymph nodes become enlarged.
2. Prodromal stage (one-five
days before rash). A mild prodromal period may occur but this is
often absent in young children. It is characterized by anorexia (loss of
appetite), malaise,
conjunctivitis, headache, and minimal respiratory symptoms. Enlarged tender
lymph nodes
four-ten days before rash. Viremia is evident.
3. Exanthem. As the prodromal
symptoms diminish, the rash appears. The exanthem consists
of a discrete, pink, maculopapular eruption that begins on the face, spreads
rapidly
downward, over the trunk and extremities, often within hours, and fades
in the same order
in which it evolved. By the end of the second day, the face may be clearing
and previous
discrete rash on the trunk may be nearly confluent. At this stage, rubella
is often confused
with scarlet fever, although the exanthem usually remains discrete on the
extremities. The
rash may persist four-five days but it generally disappears by the end
of the third day. The
rash is non-blanching and does not appear on the palms and soles.
A low grade fever may
accompany the rash. Forchheimer spots consisting of small, red macules
on the soft
palate, often precede or accompany the rash. These are not diagnostic as
they also appear
in scarlet fever, roseola, infectious mononucleosis and septicemia. Neutralizing
antibodies
become detectable coincident with the rash and generally last a lifetime.
PREVENTION:
An attenuated live rubella virus vaccine is currently
available. Administer to children between the ages of one and puberty.
Because the effect of vaccine virus on the human fetus is unknown, susceptible
women of childbearing age should be vaccinated only when extreme precautions
have been taken to prevent pregnancy before and during the two months after
administration of the vaccine. The vaccine is usually a trivalent one consisting
of measles-mumps-rubella (MMR vaccine) and is given in a single injection
at 15 months of age.
CONGENITAL RUBELLA
In 1941, after an epidemic of rubella in Australia, it was noted that children born of mothers who had rubella during the first trimester of pregnancy exhibited certain unique features:
) 1. Small and ill-nourished
(low-birth weight)
Congenital
) 2. Congenital cataracts
and glaucoma
) 3. Congenital heart disease
rubella
) 4. Mental retardation
) 5. Deafness
syndrome
) 6. Purpura
DIAGNOSIS:
1. History of rubella during first trimester of pregnancy.
2. Isolation of rubella virus from fluid obtained by amniocentesis.
3. Presence of rubella IgM antibodies during the first six months of age.
4. Presence of IgG rubella
antibodies after six months of age.
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