5.1 Clinical aspects

5.1.1 Incubation

The average incubation period is 10 days (8 to 13 days) from the date of exposure to the virus to the onset of the first clinical signs.

5.1.2 Clinical presentation

Prodromal phase

This phase lasts 2 to 4 days.
– fever with temperature over 38 °C, often over 39 °C;
– cold-like symptoms: non productive cough and/or coryza (runny nose) and/or conjunctivitis (red eyes with discharge);
– Koplik’s spots: tiny bluish-white spots (2 to 3 mm) on an erythematous base, found on the inside of the cheeks. They appear 1 to 2 days before the rash, and last 2 to 3 days. This sign is specific of measles infection, but hard to identify. Observation of Koplik's spots is not required for diagnosing measles.

Measles rash

Begins an average of 14 days after exposure, and lasts 4 to 6 days.
– erythematous, nonpruritic maculopapules that blanch under pressure; they may coalesce
into patches separated by healthy skin;
– the rash starts at the forehead and spreads progressively downward to the face, neck, chest, abdomen, and lower extremities over 3 to 4 days.

At the same time, the cold-like symptoms improve. If there are no complications, the fever disappears once the rash reaches the feet. The rash then gradually disappears and the skin desquamates.

Recovery phase

Pigmented skin takes on a tigroid appearance, and then desquamates intensely for 1 to 2 weeks.

5.1.3 Differential diagnosis

Rubella (accompanied by posterior cervical lymphadenopathy), erythema infectiosum, roseola infantum (transient rash involving mainly the trunk), infectious mononucleosis, scarlet fever, epidemic typhus, certain rickettsial infections, medication-related erythema, etc.

5.1.4 Acute complications

Measles can have a number of complications1 21. 75% of measles cases experience at least one complication. Most deaths are due to complications.

Respiratory and ENT complications (viral or bacterial)

In children under 5 years, these are the most common complications, both during and after the disease.
In adults, pulmonary complications are less common, but more severe than in children.

Acute otitis media
5 to 15% of measles cases are complicated by acute otitis media.

Pneumonia
5 to 10% of patients have pneumonia.

Acute laryngotracheobronchitis (croup)
Croup is a potential complication in children. Most children have moderate, self-limited disease lasting 2 to 5 days. Children should be monitored during this period, however, because their general and respiratory status can deteriorate rapidly.
Symptoms of croup include a characteristic "barking" cough, hoarse crying or voice, difficulty breathing, and a high-pitched inspiratory wheeze (inspiratory stridor) caused by inflammation and narrowing of the larynx.
Croup is considered benign or “moderate” if the stridor occurs when the child is agitated or crying, but disappears when the child is calm.
Croup is severe when the stridor persists at rest or is associated with signs of respiratory distress.

Ocular complications22

Eyes are usually red with a watery discharge. These symptoms are typical and benign, and are not considered a complication.
The most common ocular complications are bacterial infections and xerophthalmia due to vitamin A deficiency2 .
Diseases that cause corneal lesions (keratoconjunctivitis, keratitis, and xerophthalmia) may compromise the eye integrity and can progress to irreversible blindness.

Purulent conjunctivitis
Purulent conjunctivitis is the most common – and most benign – complication.

Infectious keratitis and keratoconjunctivitis
These infections are less common. They cause the cornea to lose its transparency or shininess. When a fluorescein test can be done to confirm the diagnosis, the exam shows a single corneal erosion or ulcer3 .

Xerophthalmia
Xerophthalmia can be detected in any the following stages: Bitot’s spots, corneal xerosis (dry, dull cornea), keratomalacia (opaque, softened, or perforated cornea).

Gastrointestinal complications

Diarrhoea
Diarrhoea is a common complication during and after the disease. It can rapidly lead to dehydration, especially in children.

Oral lesions (stomatitis)
Stomatitis is usually due to Candida albicans. Herpetic gingivostomatitis may occur.

Neurological complications

Seizures
Seizures are the most common neurological complication.

Acute measles encephalitis
This is a rare complication, occurring in 1 out of every 1000 to 2000 cases, about 3 to 6 days after the rash first appears. Symptoms include: recurrence or persistence of the fever, meningeal symptoms, impaired consciousness and seizures.

5.1.5 Other complications

Immediate

Thrombocytopenic purpura may develop 3 to 15 days after the rash appears.

Post-measles

– Measles can lead to malnutrition in the weeks following infection.
– Children are at high risk of death for several months, due to the temporary immune deficit that accompanies measles (increased risk of diarrhoea and respiratory infection).
– Noma (gangrenous gingivostomatitis) is a rare but extremely severe, non specific complication of measles. It affects malnourished children under age 4 years. It begins with severe, foul-smelling oral ulcers.

Delayed

Subacute sclerosing panencephalitis is a very rare complication (1/100,000 cases) that occurs long after the initial infection (an average of 7 years).

5.1.6 Co-morbidities

Acute malnutrition

Malnourished children are at risk for developing severe complications.

HIV infection

Measles tends to be severe and prolonged in immunodepressed people. The skin rash may be absent.
There are two particularly fearsome complications: giant cell interstitial pneumonia and measles inclusion-body encephalitis. The main cause of death in children is the pneumonia, and in adults, the encephalitis.



Footnotes
Ref Notes
1 Complications are related to epithelial changes (pulmonary and gastrointestinal) and to temporary, measles-related immune suppression.
2 In addition to ocular lesions, vitamin A deficiency weakens the immune system.
3 The normal cornea does not stain with fluorescein; if there is epithelial loss, fluorescein stains the lesion green.