A 14-month-old female is brought to your office with a 3-day history of a fever of 104 degrees rectally. Suddenly, today, the fever stopped and a rash developed. Examination reveals a diffuse, fine, maculopapular rash. Presently, the child does not appear ill. The most likely diagnosis is:
This is typical for Roseola. Rubella has a mild illness with a fine macular rash. Rubeola (measles) is an acute illness, the child is toxic, has conjunctivitis and Koplik spots. Fifth's disease has mild illness with a "lacy" rash on the extremities. Chickenpox has vesicles.