This 19 month old girl was brought in for 4 days of fever to 104 degrees (40C). She was slightly irritable, but otherwise active, well-appearing, and alert. The mother was concerned about the fever, but this morning the fever broke abruptly. However, you do notice this rash, starting on the neck and trunk and spreading to the face and extremities. It is blanching, flat, and not itchy.
Challenge: What's the cause of these symptoms?
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