well, the flip side to what I posted earlier is that, of course, your chances of being exposed at wdw are higher than they would be if you stayed at home and didn't come in to concat with anyone from the outside world. But is it enough of a higher risk to actually matter? Let's see, there have been 62 cases in the US, according to CNN, my understanding travelers that travelers from hong kong and china, and health care workers at greatest risk. Now, with, say 300 million or so people in the US, that is about .00000002% of the poeple in the US. What are the chances? Or, with 1,613 world wide cases, and 8 billion people, that is something like .0000002%. These figures aren't deaths, they are diagnosis.
I wasn't dismissing it lightly to say that you would likely be in more danger of having a car wreck on the way there, or getting hit by lightning - I'm saying that just deciding to go anywhere (or not to go anywhere, for that matter) has a certain degree of risk - that risk is very real, although quite small enough that most of us would choose to accept it. Every choice is a matter of weighing the odds about your survival, it is just that often the odds are so very small that it isn't really considered. At least as it stands now, I think that this is one of those cases, ymmv. If there is a large outbreak in the US I would certainly reconsider. FWIW, over the past 30 years, an average of 92.5 people have died each year from lightning strikes. 40,000 people die every year in the US in traffic accidents. This isn't the number of people in accidents or the number of lightning strikes, it is the number of deaths.
SO, again, I think there is more of a chance of being in an automobil accident or getting struck by lightening than contracting SARS by visiting wdw. "You will be outside a good percentage of the time in a region that has frequent lightning strikes, and you will be driving in a region with some crazy drivers." Again, ymmv.
Moreover, I'm not the OP's child's pediatrician, and am not making any recommendations about the child's health; that certainly is something to discuss with the child's physician.
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