Not in answer to your question but ...
What kind of country STILL can you not drink the water? Everyone drinks bottled water and soft drinks because the water is undrinkable.
Do we really have to wonder WHY the flu is worse in Mexico!
It could also be that some of the thousands of folks from Asian countries brought the virus to Mexico as they passed through trying to cross our border. Seems like a real possibility since this is the first known major flu outbreak for Mexico.