It seems ludicrously specious to claim tropical conditions in Ushuaia as the cause
That really doesn't make a lot of sense, I think, at least not for hantavirus. Yes, for dengue and yellow fever, but hantavirus has been endemic to the south of Argentina and Chile for a very long time.
I don't know how it is here in Argentina, but in the south of Chile the health ministry runs campaigns every spring to warn people of the danger, as they go out to their bungalows, cabins, and sheds that were closed up during winter and might have housed the rats. It's surprisingly easy to kill off the virus, the recommendation is to open all the doors and windows and let in fresh air, and particularly sunlight. The virus doesn't survive exposure to ultra-violet light. [This is all from my memory of the south of Chile, don't expect medical references].
That's why this outbreak is strange, it's entirely the wrong time of the year, and where did the initial victims find the rats? I didn't know there was a variant with human-to-human transmission, that's new to me. And, of course, slavishly following the lead of the orange man and his retribution tour agenda, Argentina has just left the WHO

so there's officially no health coordination or information sharing with the outside world now.