It was in that region that Alexander the Great died of fever, and as one Greek writer put it, "the poison was water."
Many of these fevers will spread among the troops anyway, in these summer months. I do not know why they timed the invasion for summer. Also, the mosquitos come out in armed battalions, carrying every form of malaria, often drug resistant.
You should see the look on people's faces when I tell them we eat in Tijuana when I make my perscription medicine run. Knock on wood, so far so good. There is a little stand right under the walk over bridge that sells great tacos, among other things. They shave the meat off an undetermined animal leg, pile it on homemade tortillas. You can then go to the condiment stand and pile on cabbage, fresh salsa, and guacamole. Wash it down with genuine Dos Equis or Corona. Mmmmm goood :)