Rubella
Rubella (German or three-day measles) is an important childhood
disease that is now very infrequent. Rubella in early pregnancy may cause
the congenital rubella syndrome. Rubella virus is an RNA virus.
Humans are the only natural host of rubella virus, which is spread either
by oral droplet or transplacentally to the fetus, causing congenital
infection. The peak incidence of rubella occurs among susceptible
teenagers and young.
Clinical Manifestations
The incubation period is 14–21 days. The prodromal phase of mild
catarrhal symptoms is shorter than that of measles and may be so mild
that it goes unnoticed. Approximately two thirds of infections are
subclinical.
The most characteristic sign is retroauricular, posterior cervical, and
postoccipital lymphadenopathy. No other disease causes the tender
enlargement of these nodes to the extent that rubella does. An enanthem
appears in 20% of patients just before the onset of the skin rash.
Lymphadenopathy is evident at least 24hr before the rash appears and
may remain for 1 wk or more. The exanthem is more variable than that of
rubeola. It begins on the face and spreads quickly. Its evolution is so
rapid that the rash may be fading on the face by the time it appears on the
trunk. Mild itching may occur, the eruption usually clears by the third
day, and desquamation is minimal. In contrast to rubeola, there is no
photophobia. The spleen is often slightly enlarged. Especially in older
girls and women, polyarthritis may occur with arthralgia, swelling,
tenderness, and effusion but usually without any residuum. Any joint may
be involved, but the small joints of the hands are affected most
frequently.
Diagnosis
The diagnosis of rubella may be apparent from the clinical symptoms
and physical examination, but it is usually confirmed by serology or virus
culture.
Treatment
There is no specific antiviral therapy; treatment is entirely supportive.
Post-exposure prophylaxis
For the susceptible pregnant woman exposed to rubella for whom
abortion is not an option, immunoglobulin should be administered in a
dose of 0.55mL/kg, which reduces the attack rate but does not eliminate
the risk of fetal infection.