Measles is a highly contagious respiratory infection that's caused by a virus that infects only humans.  It is transmitted by respiratory droplets and direct contact with nasal or throat secretions of infected persons. 

The incubation period of measles ranges between 7 and 18 days and patients are infectious from about 4 days before developing the rash until 4 days after rash. The illness is presented by high fever, generalized rash, and cough, coryza (runny nose) or conjunctivitis (red eyes).

Complications of measles include viral and bacterial pneumonias and severe diarrhoea. The disease can also lead to lifelong disabilities including brain damage, blindness and deafness.

Measles kills more children than any other vaccine-preventable disease.  Before the widespread use of vaccine, 90% of children had contracted measles by the age of 10 years. An effective vaccine has been available since the 1960s, and all countries offer measles-containing vaccine (MCV) in their immunization programmes.

Measles is highly transmissible; almost all non-immune children contract measles if exposed to infection. Poorly nourished children and those whose immune systems have been weakened by HIV/AIDS or other diseases are severely at high risk of developing measles complication and death.

Measles occurs worldwide and it is still a significant cause of childhood morbidity and mortality despite the existence of effective vaccine. Measles infection has its greatest incidence in children below 2 years of age in the developing countries.