Rubella

Definition/diagnostic criteria Rubella, also known as German measles, is a viral infection characterised by a distinctive red rash. It is caused by the rubella virus and is typically a mild illness, but it can have serious consequences if contracted by pregnant women due to the risk of congenital rubella syndrome (CRS) in the developing foetus. Diagnosis is primarily clinical, supported by serological testing.

Epidemiology Since the introduction of the MMR (measles, mumps, and rubella) vaccine, the incidence of rubella in the UK has significantly declined. However, outbreaks can still occur, particularly in communities with low vaccination coverage. The World Health Organization (WHO) European Region, including the UK, was declared free of endemic rubella transmission in 2016. Nonetheless, vigilance remains crucial due to the possibility of importation of cases from other regions.

Diagnosis
Clinical features: Rubella typically presents with a maculopapular rash that starts on the face and spreads downwards. Other symptoms include low-grade fever, lymphadenopathy (particularly posterior auricular and suboccipital lymph nodes), arthralgia, and conjunctivitis. These symptoms are often mild and may be overlooked, especially in children.

Investigations: Laboratory confirmation is essential for accurate diagnosis. Serological testing for rubella-specific IgM and IgG antibodies is the primary diagnostic method. A positive IgM antibody test indicates recent infection, while IgG antibodies suggest immunity due to past infection or vaccination.

Rubella virus RNA can be detected by RT-PCR in certain cases, especially in pregnant women.

Treatment There is no specific antiviral treatment for rubella. Management is primarily supportive, focusing on relieving symptoms such as fever and pain. Paracetamol can be used for fever and myalgia.

In the case of pregnant women exposed to rubella, post-exposure prophylaxis with rubella-specific immunoglobulin (IG) may be considered in women under 20 weeks gestation, although its effectiveness in preventing CRS is uncertain.

Prognosis The prognosis for rubella in children and adults is generally excellent, with most individuals recovering fully without complications. However, the greatest risk is to the foetus in a pregnant woman, where infection, particularly in the first trimester, can lead to CRS. CRS can result in a range of severe congenital anomalies including deafness, cataracts, heart defects, and neurological impairment.