Thirdly we noted the difference in the median age of 15 years in the first 977 cases to the median age of 21 years in patients notified through the general practice surveillance scheme [32] , and suggested this implied an amplification of an established epidemic in school-aged children. We have now supported these three arguments with modelling of the Victorian and WA notification data and two further circumstantial observations related to Victoria, namely, export of a case to China and an outbreak on a cruise ship in which the index case was a Melbourne resident.