I'm surprised they don't mention why or how this is the first time a 25-year old virus that affects birds made it to the Antarctic for the first time this year

Edit: I've read four different articles about this but none of them mentioned the how or why. But apparently H5N1 just arrived in South America last year and migratory birds from Antarctica, and bringing it back yourself, and now it might reach the mainland Antarctica, and kill seals and birds. This is nuts