Measles is a viral infection that is characterized by a one distinctive symptom: the rash. However, the rash is just one stage of the virus. Measles occurs in five distinct stages: the incubation phase, the prodromal phase, the Koplik spots phase, the rash phase and the recovery phase.
Like most illnesses, measles has an incubation phase. The incubation phase for measles is fairly long, at 11 to 12 days from exposure to the onset of the initial symptoms. From exposure to the onset of the rash, the latency period is even longer, at an average of 14 days. However, it can range from as few as seven days to as many as 21.
The prodrome phase is the phase in which typical illness symptoms start to occur. “Typical symptoms” that occur during this phase include a high fever (at between 40 to 41 C), cough, runny nose, sore throat, muscle aches, fatigue and watery eyes. This stage develops at between 11 to 12 days after exposure and lasts for an average of two to four days. However, as with the average latency phase for the rash, the duration of symptoms varies considerably. Some people experience these symptoms for just one day, while others experience symptoms for as many as seven days.
Two to three days after the prodromal phase begins, most measles patients develop Koplik spots. Koplik spots are little white spots that appear in the mouth and that have a red border and bluish centre.
Once the Koplik spots show up, the typical measles rash starts to develop. In most cases, the rash breaks out three to five days after prodromal symptoms begin. The measles rash usually develops on the face first, along the hairline, and appears as flat red spots. It then spreads downward, to the neck, chest, torso, arms, legs and then feet.
In many cases, the spots develop blisters, which appear as small raised bumps along the top of the flat spots. When the rash is at its peak, the spots may join together to form giant spots.
When the rash appears, a person’s fever may spike. In many cases, the average body temperature for measles patients in the rash stage is 40 C.
Approximately four to five days after the rash begins, it and other symptoms begin to subside, marking the beginning of the recovery stage. In some cases, the rash leaves flaky skin behind in its place. Most healthy children and adults are back to normal activity levels within 10 to 14 days of the initial onset of symptoms.