MM 499-502; ID 903-911
 

NAME OF DISEASE:          Rubella
                                                    German measles
                                                    Three-day measles

OVERVIEW:

Man is the only host. The disease is spread by droplet inhalation with an attack rate highest in the 5-9 year old group but the disease can occur in anyone up to 35 years of age. In most cases the disease is a relatively mild disease with the major symptom a rash.
 

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 per mm³, 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. Hemorrhage (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.
 
 

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
                                      rubella )     3. Congenital heart disease
                                 syndrome )     4. Mental retardation
                                                )     5. Deafness
                                                )     6. Purpura
 

DIAGNOSIS:

1. History of maternal 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 life.

4. Presence of IgG rubella antibodies after six months of age.