MSRA-0250

A 5-year-old girl is brought to the pediatrician’s office by her father, who is concerned about a red rash on her arms and chest. She has been feeling sick, with cold-like symptoms preceding the rash. The rash is erythematous, macular and symmetrical to both arms and chest and is non-blanching. She is currently without fever and appears to be in good health.
What is the most probable cause?