The measles virus resides in the mucus in the nose and throat of infected people. When they sneeze or cough, droplets spray into the air and the droplets remain active and contagious on infected surfaces for up to two hours.
Measles is a highly contagious disease, and about 90% of non-immunized persons will develop measles if they live in the same house as someone who has the disease. The measles virus can be spread to other people from airborne droplets of fluid from the nose or mouth. People with measles are usually contagious from about 5 days after exposure to about 5 days after the rash appears.
Diagnosis of measles is usually based on the symptoms. Various laboratory tests may help with the diagnosis, but they are usually unnecessary.
In some cases, if your doctor suspects that you or your child has measles, a virus culture or serologic blood test may be needed. This blood test can detect measles antibodies, which indicate whether you have had a recent or past infection of the disease.
If you suspect that you or your child has measles, then contact your doctor as soon as possible to avoid the risk of developing complications or spreading the disease.