Hello Mrs,
Unfortunately, it is impossible to determine with certainty the cause of your child's symptoms, as this requires a diagnosis that can only be made by a doctor.
For the moment, if your child has a fever and/or headache, your best solution to soothe is acetaminophen (Tylenol, Tempra and other brands). Your pharmacist will be able to tell you how much to give your child according to his weight and the concentration of the product chosen.
Gravol can also help relieve nausea, and is available in different forms as an oral liquid or rectal suppository.
Encourage your child to drink cold or hot liquids, depending on his or her preference, but in frequent small amounts.
In most cases, it is a virus that is the cause and the episode goes away by itself. If you don't see any improvement 7 days after the onset of symptoms, or if the fever lasts more than 3 days, you should see a doctor.
I hope this helps, and I am available if you have any further questions!
Tom Samaha, pharmacist