I got sick on my Honeymoon in Puerta Villarta....and we were doing everything possible to not expose ourself to water, etc....
Americans have no resistance built up to Mexican bugs. Mexicans who come here have little resistance to American bugs and get sick in the same way. If you ate anything in Mexico that was not cooked, or consumed a drink with ice in it, or didn’t use bottled water to brush your teeth, you exposed yourselves. Luckily, after one episode you usually are immune to whatever made you sick. That’s not to say a different bug won’t get you the next time. When I was a child we traveled to Mexico occasionally. I got sick the first time, but never again. My nana, who was from Mexico City but who had lived in LA for decades, got sick every time. Go figure.
You mean you stayed in bed the whole time???
most likely the plane ride over. You are breathing everyone on that planes air.