You've had a busy but fairly routine morning at the pediatric clinic.

"Doctor, you should see this boy next", your nurse says, ushering the next patient in. You are introduced to five-year-old Austin, accompanied by his father and stepmother.

Austin has had fever, nasal congestion, and red eyes for the last three days. Late last night, he developed a red rash on his face; today, this had spread to encompass his entire body. He also started coughing and breathing rapidly. This prompted his father to seek medical advice.

His only treatment has been acetaminophen (paracetamol) six-hourly for the last two days, based on his stepmother's assumption that he had "the flu".

His medical history is significant for a single episode of otitis media at the age of three, which was successfully treated with a course of antibiotics. Growth and development are both normal.

He has not been administered the MMR vaccine, as his father and stepmother both believe that vaccination is harmful. His three-year-old sister, Dawn, has not been vaccinated against MMR either.