From the comments, at Effect Measure

It surprises me that no one has mentioned this, so i'll end years of
quietly lurking and say it myself: a possible explanation for the
difference in clinical picture here vs Mexico lies in the sample size
here. 8 of 8 confirmed "swine flu" cases here have not involved serious
lower respiratory infection or death. But about 60 of about 1,000
generally unconfirmed cases of "swine flu" in Mexico have. If those all
confirm, that's about a 6% CFR. From what i've read, we don't have data
yet on the CFR of confirmed cases in Mexico, and we don't have a
satistically significant sample here for measuring phenomena in the
single percentage digits.

This tells me that there is no confirmed or statistically
significant difference in the clinical picture between US & Mexico.

Of course Mexico is where most of the data points lie.  That's Suzanne Bunton.  Read the other comments too.  If the Obama administration believes in competent government, it would be nice if they would meet the public health standards currently practiced by the government in Mexico.  Even a completed fence would not stop a virus and there is otherwise no reason to wait.  Should we in the meantime count on a more favorable mutation to protect us?