For measles, there is an average of 10 to 12 days from exposure to the appearance of the first symptom, which is usually fever. The measles rash doesn’t usually appear until approximately 14 days after exposure (range: 7 to 21 days), and the rash typically begins 2 to 4 days after the fever begins. The incubation period of mumps averages 16 to 18 days (range: 12 to 25 days) from exposure to onset of parotitis. The incubation period of rubella is 14 days (range: 12 to 23 days). However, as noted above, up to half of rubella virus infections cause no symptoms.