4 Clues

1. I am a viral infection that tends to affect young children.
2. I have an incubation period that ranges from 4 to 28 days. During this time I am very contagious and those I have infected have no idea that they are infected.
3. My most visible symptom is a red blush or sunburned looking rash appearing over both cheeks. But, I also give cold-like symptoms and a low grade fever.
4. I have infected at least two babies in Jayla's classroom and I hear that Jayla had a low grade fever yesterday along with a runny nose and a cough.
   
   Who am I?