Measles (rubeola) is a highly contagious acute viral respiratory illness. It is characterized by an early symptom of fever and fatigue, cough, rhinitis, conjunctivitis, and Koplik spots followed by a maculopapular rash. The rash usually appears about 14 days after a person is exposed, however the incubation period ranges from 7-21 days (average 10-12 days). The rash characteristically spreads from the head to the trunk to the lower extremities. Suspected cases and confirmed positive cases are considered to be contagious from four days before to four days after the rash appears. 

While it is rare for vaccinated individuals to develop measles, it can happen. Vaccinated individuals may have an atypical clinical presentation. This could look like a shorter duration of rash or atypical rash presentation, and possible lack of fever, cough, rhinitis, or conjunctivitis.

People at high risk for severe illness and complications from measles include infants and children <5 years, adults ages >20 years, pregnant women, those with compromised immune systems, and those individuals that have not received the Measles, Mumps, and Rubella (MMR) vaccine.