Measles Causes

Both the rubeola and rubella viruses are spread through the respiratory route. This means they are contagious through coughing and sneezing. In fact, the rubeola virus is one of the most contagious viruses known to man. As a result, it can spread rapidly in a susceptible population. Infected people carry the virus in their respiratory tract before they get sick, so they can spread the disease without being aware of it.

If people are immune to the virus (either through vaccination or by having had measles in the past), they cannot get the disease caused by that virus. For example, someone who had rubeola as a child would not be able to get the disease again. Remember that rubella and rubeola are different viruses. An infection with one of these viruses does not protect against infection with the other.