Are there any sure signs of measles?
Q - Many clinical cases of 'measles' prove not to be when antibody status is checked. What might the viral causes be and are there any clinical pointers?
A - Viral rashes, particularly in children, which could be mistaken for measles are rubella ('third disease' German measles), parvovirus B19 ('fifth or slapped cheek disease' erythema infectiosum) and human herpes virus 6 and 7 ('sixth disease' exanthem subitum or roseola infantum).
Other viral causes of rash illness, not confined to children, include Epstein-Barr virus, cytomegalovirus, HIV, adenovirus and enteroviruses (echovirus and Coxsackie virus).
Some clinical features strongly characterise each disease, which may assist in clinical diagnosis: the presence of Koplik's spots (clusters of bluish, white papules, with an erythematous areola) on the buccal mucosa, opposite premolar teeth, on or after
the second day of febrile illness, is classical of measles.
In rubella, enlarged postauricular, suboccipital and posterior cervical nodes, which may be tender, are characteristic. The facial appearance of 'slapped cheeks', with discrete erythematous, ring-like macules on the extremities, strongly suggests erythema infectiosum.
Exanthema subitum tends to occur in the very young (six to 24 months), with high fever (up to 40°C), the blanchable, macular-papular rash only appearing after the temperature falls, distinguishing this from other viral exanthems.
Ultimately, clinical diagnosis may need confirmation by the detection of a viral-specific antibody response, viral culture or viral nucleic acid detection. In some cases confirmation of the diagnosis will be more urgent.
Julian Tang, clinical lecturer and honorary specialist registrar, and Nicola Brink, consultant virologist and honorary senior lecturer, department of virology, UCLH