A mother brings her 15-month-old daughter to your office for evaluation of a rash and fever. She says the rash started one day and the fever developed the next day. Her daughter has had all of her vaccinations up to 10 months. The mother sheepishly admits that she hasn't had time to bring her daughter in since her 10-month check-up. On examination you see a mildly sick- appearing toddler with a 102-degree temperature. Looking at her skin you see at least 100 of a variety of papules, vesicles, and ulcers in different stages of development. What illness prevented by proper vaccination does this toddler have?
A) Varicella (chickenpox)
B) Measles
C) Smallpox