Why we don't know more

CDC is, if nothing else, very thorough and cautious.

When an outbreak is first identified, there are enormous amounts of information that must be gathered and analyzed in order for the epidemiologists to draw rational conclusions. It is easy to jump ahead before we have all the information, but they are scientists - the best in the world.

That is why acting director Richard Besser prefaced his comments with a few important points:

First, CDC is concerned, very concerned, as the information becomes available. However, uncertainty at beginning of an outbreak is normal and to be expected. This is a fluid situation, and they are working with international partners to gather data and issue information.

Second, CDC's guidance is likely to change as we learn more. While this may be confusing or appear to be conflicting with older information, it is the reality of an ongoing epidemiological investigation. And this is just the beginning.

CDC really wants to get into Mexico and start its investigation so it can get firsthand information. So, more will be revealed...