I was thinking along these lines, too. There are several cases where children of Mexican heritage died very rapidly from this flu. Ethnically, it seems this population has little or no resistance, as compared with Northerners.
This reminds me of the measles epidemic which wiped out so many native Americans after the voyages of the Europeans introduced this “new” virus to indigenous populations.
This should be a matter for further investigation.
Early on it was primarily blacks and hispanics, but looking at the kid’s photos, it appears the demographic could be changing somewhat. This is really the only clue that we have (or that is made public):
http://singtomeohmuse.com/viewtopic.php?t=3649
OR, are they less likely to get yearly flu vaccines or pneumonia vaccines?