i think you'll find Madam was hinting early on that it appeared no to be any where near as contagious in Oz as elsewhere -this appears to clearly be the case - and its not our better cleaning of public spaces and cafe tables!! Even before this, I was shocked at the number of cafes who wouldn't clean tables between customers!!
Not many mention our higher levels of light (generally) , perhaps not as much underground transport, and maybe not as many people use. I'm just guessing!