Rubella (German measles)

Definition

Rubella is a usually mild infectious disease caused by the rubella virus (family Togaviridae, genus Rubivirus), with a fine macular rash and lymph node swelling. Its main significance lies in infection during pregnancy, which can lead to congenital rubella syndrome (CRS).

Occurrence & epidemiology

Humans are the only natural host. Transmission is usually by droplets; the incubation period is 14–21 days. Patients are infectious from 7 days before to 7 days after the onset of the rash. Up to 50% of infections are asymptomatic. In Germany rubella has been considered eliminated since December 2020 and now occurs only very rarely.

Clinical features

• Prodrome (more common in adults): headache, low-grade fever, conjunctivitis, upper respiratory catarrh.
• Lymph node swelling, especially nuchal and retroauricular.
• Rash: fine, macular to maculopapular, pink to light red (spots about 2–3 mm); starts on the face, spreads over the trunk and limbs and fades after 1–3 days.
• Forchheimer sign: petechiae on the soft palate and uvula during the prodrome.
• Arthralgia and arthritis mainly in adult women; rarely thrombocytopenia with purpura or encephalitis.
• Congenital rubella syndrome: infection in the first 12 weeks of pregnancy damages up to 90% of fetuses; classic Gregg triad of heart defect, cataract and sensorineural deafness; the skin may show a "blueberry muffin" pattern.

Diagnosis

• A purely clinical diagnosis is unreliable (similar rashes occur in measles, erythema infectiosum and scarlet fever, among others); every suspected case is confirmed in the laboratory.
• RT-PCR from throat swab and urine, as soon as possible after the rash appears.
• Serology: IgM antibodies (positive in over 90% from about day 5 after symptom onset; false-positive results possible) or a marked (more than 4-fold) rise in IgG in two samples taken 10–14 days apart.
• Notifiable by name in Germany (suspicion, illness, death, pathogen detection).

Differential diagnoses

• Measles
• Erythema infectiosum (fifth disease)
• Roseola infantum (exanthem subitum)
• Scarlet fever
• Amoxicillin rash in infectious mononucleosis
• Acanthosis nigricans maligna

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References (selection)

1. RKI-Ratgeber: Röteln
2. DermNet: Rubella

Cross-references