Measles

What it is

Measles is one of the common childhood infections with exanthems, a group that also holds rubella, mumps, varicella, fifth disease, roseola and scarlet fever. It has three parts: the prodrome, the enanthem inside the mouth, and the exanthem on the skin. It is a highly contagious viral disease, an RNA paramyxovirus; the measles virus is a single-stranded, enveloped, RNA virus. Spread is by droplet, and it is highly infectious during viral shedding, with days 10-14 between exposure and illness.

How it presents

The prodrome is cough, coryza, conjunctivitis and high fever. The fever is not always high: in one described example, a boy of nine months had mild fever for 5 days along with coryza, exudative conjunctivitis and cough, with an erythematous maculopapular rash spreading from head to toe and small irregular red spots on the buccal mucosa.

The enanthem is the Koplik spots, white spots on the buccal mucosa seen against a bright red background.

The rash is erythematous macules and papules. It begins on the forehead, the hairline and behind the ears, then extends cephalocaudally, so that macules run from the hairline, face and neck to the trunk and the extremities, spreading from head to toe. The two signs are set out at greater length elsewhere. Koplik's spots are white spots on buccal mucosa seen against a bright red background, pathognomonic but difficult to see, and named again as the bluish-white Koplik's spot. The rash spreads downwards, from behind the ears to the whole of the body: a discrete, maculopapular rash initially, which becomes blotchy and confluent and may desquamate in the second week. It is also called a morbilliform rash, and a descending rash for the way it travels.