Crowds at the MCG for the Boxing Day Test. - AAP 1 of 1 5370537724001 Tens of thousands of cricket fans and Boxing Day shoppers are being asked to get tested and self-isolate, following Victoria's first mystery coronavirus case in more than two months. Health authorities are scrambling to find the source, with a man in his 30s catching the virus after attending the sales at Chadstone Shopping Centre on December 26 and the Boxing Day Test at the MCG the following day. Chadstone and the MCG, billed as the largest shopping centre and sports stadium in the country, have now been listed as possible transmission sites.