The 2009 A / H1N1 was also a derivative of two
different strains of
swine influenza — one that had been circulating in Europe and Asia and another that was circulating in the Americas, especially North America.
Although respirator use made sense at the beginning of the
swine flu pandemic, it now appears that H1N1 behaves similarly to seasonal
influenza, Dr. Rupp says, so «it does nt make much sense to be using
different precautions for seasonal flu than we use for H1N1.»