Measles

Introduction


Measles, a disease recognised for over two thousand years, is a highly contagious, acute infection caused by the rubella virus. It usually occurs in children. It is seen in every country of the world. Before the use of vaccines, epidemics of measles occurred every two to five years. Cough, cold, fever and a skin rash that begins several days before the initial symptoms characterise the illness. Recovery from measles is usual, but serious complications of the respiratory and central nervous system may occur.





Cause and Pathogenesis

Measles virus belongs to the Morbillivirus group of the Paramyxovirus family. Humans are the only natural host for wild measles virus. The virus is easily destroyed but remains in the droplet form in air for several hours, especially under conditions of low relative humidity. It is spread by direct contact with droplets from respiratory secretions of infected persons. It is one of the most communicable of infectious diseases and is most infectious when cough and cold is at its peak. The virus invades the respiratory lining membrane and then enters the blood stream. It causes inflammation of the respiratory tract and may predispose to secondary bacterial pneumonia.

Symptoms and Signs


The incubation period is one to two weeks and is often longer in adults. The illness begins with symptoms of malaise, fever, loss of appetite, conjunctivitis, cough and cold lasting several days. This is followed by bluish-grey spots in the oral cavity (Koplik's spots) and then a diffuse skin rash beginning on the face and proceeding down the body to involve the extremities. The rash lasts for five days and then peeling of the skin occurs. Several days after the appearance of the rash, the fever abates. The most common complications of measles involve the respiratory tract and the nervous systems. Bacterial super-infection can also cause middle ear infection or pneumonia in severe cases. Encephalitis may be acute or chronic, after measles infection. Transient hepatitis can also occur.

Severe measles can occur in persons who are immunocompromised such as those, being treated for malignancy or those with AIDS. Malnourished children in developing countries may also develop severe measles. In pregnant women, however, measles (rubeola) unlike German measles (rubella) does not cause any congenital anomalies.





Investigations and Diagnosis

Classic measles is diagnosed when a child develops along with cough, cold, conjunctivitis, Koplik's spots and a skin rash. Leucopenia (a low white blood cell count) is common. Virus isolation in the laboratory is technically difficult. A four-fold increase in the measles antibody titre in acute and convalescent serum samples is considered diagnostic.

Treatment and Prognosis


The disease is usually self-limited, and supportive therapy such as antipyretics and fluids are indicated. Bacterial super-infection should be promptly treated with appropriate antimicrobials. Prophylactic antibiotics are not known to be of value and are not recommended.

Prevention


Measles can be prevented by administrating a live vaccine long before an anticipated exposure. It is now recommended that all healthy children be administered live measles vaccines at fifteen months of age. A second dose given in childhood, usually as a measles-mumps-rubella (MMR) is now routine. The first vaccine can be given between six and nine months of age in situations where the incidence of measles is high before the age of one year. Transient fever and rash develop about one week after vaccination in 5 - 15 percent of children. Live measles vaccine is contra-indicated in persons with defects in the cell-mediated immunity and in pregnant women.

Passive immunisation with antibodies is recommended for those at high risk of developing severe measles and for those who have been exposed to the infection. For example, children with malignant disease and those with defects in cell-mediated immunity. To be effective, passive immunisation must be given within six days after an exposure.