Here is a helpful Google map [Update: 5/3/09: This map has been moved here]you can use if your class is following the spread of the swine flu. It differentiates between suspected and confirmed cases. It also shows casualties.
I've been checking the map periodically over the past few days and it's interesting to see how it is spreading. Scary when you realize each of the markers is a real person who is sick and that some of them denote deaths.
Right now it looks like the majority of cases outside of Mexico have been spread via air travel. I am sure you could locate major airports near each outbreak. Have your students predict how it can spread from there and then follow that up with a discussion on what precautions we all should be taking. Visit the CDC site to gather accurate information.
Larry Ferlazzo has a list of resources you can use in the classroom at his excellent site, Larry Ferlazzo's Websites of the Day. I suspect the kids (and us) are going to hear a lot rumours over the next few days as the seriousness of the situation is determined. Help yourself and your kids stay informed with good information.