The average incubation period for measles is 7-21 days (average 10 days). During this period, the patient does not have any clinical symptoms, so neither the patient nor their family members know they have the disease.

Measles-like rash fever in adults also needs to be alert for dangerous complications such as encephalitis causing disorders of the respiratory circulatory centers.

Respiratory complications are the most common complication of measles, usually occurring within 30 days of the rash. Pneumonia is the leading cause of death from measles in developing countries.