Measles is a viral infection caused by measles virus of genus morbillivirus. It is one of the leading cause of mortality among children below 5 years of age.
Risk factors / high risk population
- Children who are too young to be vaccinated
- Children who haven’t been vaccinated due to medical reasons
- In people for whom the measles vaccine failed to elicit an immunization effect
- People who haven’t received the second doze of vaccine
This highly contagious infection has an attack rate of 90 percent in susceptible individual. The transmission occurs mainly due to person to person individual contact. It can also be spread via air. The infectious droplets from a patient can remain active in air for about two hours. So, there are chances of large outbreak in crowded areas.
Measles has an incubation period of about 6 – 21 days.
Measles virus infection can result in certain clinical conditions like:
- Classic measles infection in non – immunized patients
- A modified infection in an immunized individual
- atypical infection in individuals immunized with a killed or dead vaccine
Clinical manifestations are different in different clinical stages:
- Incubation period (6 – 21) days: the virus enter into our body through the respiratory mucosa and spreads to regional lymphatic tissue after replication. It then spreads into other reticuloendothelial tissue. The virus disseminate into viremia and then infection spreads into various cellular layers. Most patients are asymptomatic in this period, but some patients are reported to have fever, respiratory symptoms or rash.
- Prodrome (3 – 8) days: in this phase symptoms appear. The primary symptoms include fever that could be as high as 400C, anorexia and malaise. The secondary symptoms include cough, conjunctivitis or photophobia. The respiratory symptoms result from mucosal inflammation of the epithelial cells of respiratory tract.
- Exanthem: Exanthem is followed after a period called enanthem which is characterized by Koplik spots (describes as grains of salt with a red background). Exanthem is characterized by the formation of an erythematous blanching rash (like petechiae) which begins on face and then spreads into neck, trunk and the extremities. The rash darkens in four to five days. The palms and soles are not involved in most cases. Other clinical manifestations include lymphadenopathy, pharyngitis and conjunctivitis.
- Recovery: both humoral and cellular mediated immunity is essential for viral clearance. The immunity persist lifelong and reinfection is very rare. Cough may persist for two weeks and a lasting fever may be due to complications
- Chest radiography: demonstrates interstitial pneumonitis
- Leukopenia, thrombocytopenia and T cell cytopenia are observed
- Appearance of giant cells:
- 1. Biopsy sample of lymphoid tissue before exanthem stage
- 2. Histologic examination during exanthema
- 3. Also present in the nasopharyngeal, conjunctival and buccal epithelial cell
The differential diagnosis depends on the clinical stage. It can be mistaken with dengue fever which is diagnosed with serologic testing.
Prodromal: common viral infections: it can be mistaken with common respiratory viral infections like rhinovirus, adenovirus, parainfluenza virus and respiratory syncytial virus. Fever is more pronounced in measles and it can be distinguished using a nasal swab or PCR – polymerase chain reaction.
Fordyce spots: it can be mistaken with Fordyce spots. Fordyce spots does not occur in erythematous mucosal background.
Exanthem stage: causes of rash: varicella, roseola, enterovirus, erythema infectiosum and rubella. Measles rash can be distinguished with its brownish coloration and associated clinical maniestations.
More than one complication is found in most measles cases. They include:
- Secondary infection: an individual with measles viral infection becomes immunocompromised and leads to T cells dysfunction.
- Gastrointestinal: Diarrhea is the most common complication. Others include gastroenteritis, appendicitis, hepatitis and gingivostomatitis.
- Pulmonary: respiratory tract infections are common. Bronchitis, bronchopneumonia and laryngotracheobronchitis can occur.
- Neurologic complications: include encephalitis, subacute sclerosing panencephalitis and acute disseminated encephalomyelitis.
- Others: keratitis and corneal ulceration.
Groups at risk for complications
- Immunocompromised patients
- Pregnant women
A supportive therapy is given for measles. This include fluids, antipyretics, treatment of bacterial suerinfections like otitis and bacterial pneumonia. Other complications should also be treated accordingly.
Antibiotic prophylaxis may prevent complications.
Vitamin A supplementation improves recovery and decreases chances of complications
Role of immunization
Measles vaccination is highly protective against clinical infection. According to a statistical study an unvaccinated individual has 224 times more risk of getting infected.