Definition of Measles:

Measles is a highly contagious illness caused by a virus. Contagious means the disease spreads very easily.

Causes, incidence, and risk factors:

Measles is caused by a virus. The infection is spread by contact with droplets from the nose, mouth, or throat of an infected person. For example, sneezing and coughing can put contaminated droplets into the air. Symptoms occur generally 8 to 12 days after you are exposed to the virus. This is called the incubation period.

Persons with the measles typically have a fever, cough, redness and irritation of the eyes (conjunctivitis), and a rash that spreads. Those who have had an active measles infection or who have been vaccinated against the measles have immunity to the disease.

Before widespread immunization, measles was so common during childhood that most people became sick with the disease by age 20. While the number of measles cases dropped over the last several decades to virtually none in the U.S. and Canada, rates have started to rise again recently.

Some parents do not let their children receive become vaccinated because of fears that the MMR vaccine, which protects against Measles, Mumps, and Rubella, can cause autism. Large studies of thousands of children have found no connection between this vaccine and the development of autism. However, failure to vaccinate children can lead to outbreaks of a measles, mumps, and rubella -- all of which are potentially serious diseases of childhood.