Exanthem 1: measles
Measles occurs typically in preschool and young children with the peak incidence in late winter and spring.
• Prodrome: the p infection occurs in the respiratory epithelium of the nasopharynx, and produces fever, coryza, cough, and non-purulent conjunctivitis. Occasionally, a characteristic sign in the mouth is seen opposite the low premolars—‘Koplik spots’ (which look like grains of sugar on the mucosa). After 2–3 days there is a viraemia with infection of the reticuloendothelial system.
• Exanthematous phase: a second viraemia occurs 5–7 days after the initial infection with rash developing some 14 days after initial infection. The maculopapular rash starts on the face and lasts 6–8 days.
• Infectivity: 4 days before to 4 days after the onset of rash.
• Other features: generalized lymphadenopathy, anorexia, diarrhoea, and fever (may persist 7–10 days). Incubation 7–18 days (av. 10–2 days).
• Clinical: Koplik spots are pathognomonic, but usually seen.
• Blood film: leucopenia and lymphopenia.
• LFTs: raised transaminases.
• Oral fluid test: measles RNA on oral fluid specimen confirms the diagnosis. Serum serology may also be used.
• Acute treatment: generally supportive, but could include antibiotics for secondary bacterial infection (e.g. pneumonia, otitis media, tracheitis). Individuals are highly contagious during the viraemia.
• Prevention: MMR vaccine at 12–18mths and preschool booster to all children.
• Vitamin A: in developing countries vitamin A deficiency and malnutrition lead to a protracted course of illness with severe complications. The rash is dark red and is followed by desquamation and depigmentation. Consider supplements in children older than 6mths.
Complications commonly occur in young children with almost 20% of cases having at least one additional problem.
• Acute otitis media (10%).
• Lower respiratory tract infection (LRTI; 5%): bacterial pneumonia, interstitial pneumonia, bronchiolitis, laryngotracheobronchitis.
• Encephalitis (1 in 5000): occurs 78 days after the onset of illness and starts with headache, lethargy, irritability, followed by seizures and coma. Mortality is high and there are neurological sequelae in survivors.
• Subacute sclerosing panencephalitis (SSPE, 1/10 000). A rare and fatal neurological disease with progressive intellectual deterioration, ataxia, and seizures about 7yrs after measles infection.