Update: May 13
There is a second case in Orlando FL, and the TSA is beginning to alert travelers. A few health care workers in Orlando are in precautionary isolation (at least two, who have tested negative)/ There is another case in the Netherlands.
Update: May 16
Vox Media has a balanced perspective on MERS here. The possibility of mutation is worth noting. But it's also likely there are many (even a large majority of) mild or even asymptomatic cases that go undetected, and that the actual death rate would be orders of magnitude lower. If that;s true, exposure of the general population, to build up resistance, might be a good thing.
Update: May 17
A person in Illinois has tested positive for MERS. The person was in a business meeting with one of the index cases from Saudi Arabia and shook hands, a meeting that lasted 40 minutes. The person met briefly the next day. The person does not now have live virus and had exhibited only mild cold-like symptoms. It is beginning to look like many natural infections, maybe most, are mild. The CNN story (and another video) are here.