It has killed over 60 people in Mexico, and infected many more. In the US at first 8 have been infected so far, all in Southern California & Texas. But now there's fears that it has spread to Queens, NY after a few students visited Mexico and now around 25 people are said to be infected there.
It's a more stronger version of the human flu, but contains a combination of swine, bird, and human flu that can be spread among humans.
Remember the "bird flu" fears a couple years ago that started in Asia, and how it could become a pandemic. They're saying this could become a worldwide pandemic -- except this time it's started in our own backyard.
http://online.wsj.com/article/SB124061694466055035.html
http://www.nytimes.com/2009/04/25/nyregion/25sick.html?hp