We are currently in Cordoba... I've seen one breathing mask - but that might have been restaurant related. The news I read from US media outlets is concerning and borders on criminal.
I don't trust the US media for much of anything anymore... Trying to hype what probably is a routine flu outbreak and getting people all hysterical should land some "journalists" in prison. Note that the media does not detail the mortality rate (4%) or comparisons to other flu outbreaks. The media does not disclose these important facts because of politics.
I'm concerned about not getting back into the US when we're done visiting Mexico, but otherwise I'm pretty much at ease.