How do people get reye's syndrome?

Aspirin & virus infx: Reyes generally occurs in children between 4 and 14 years old. It has been linked to the use of Aspirin or aspirin-containing medicines used during a viral infection (i.e., chickenpox; flu, etc.). It is not well understood but can be fatal. We see less of it since doctors have started advising against giving Aspirin to kids and teens, especially during virus infections.