The national total of swine flu cases has topped 50, with the number doubling in just one day. Twenty-five new cases of the potentially deadly virus were confirmed on Tuesday – 10 each in Victoria and NSW plus five more in Queensland. The six most recent in NSW include a passenger who arrived on Qantas flight QF12 from Los Angeles to Sydney on Sunday, and another five people off the PO cruise ship Pacific Dawn. It berthed in Sydney on Monday and offloaded nearly 2000 passengers. At least 172 …