Measles
Introduction
Cause and Pathogenesis
Symptoms and Signs
Investigations and Diagnosis
Treatment and Prognosis
Prevention
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.
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