I AM LEGEND

Skye and I just watched this movie. While I was totally scared to death, and I am just like my mom and shouldn't put those images into my mind, I couldn't stop watching and wanted to know how it was going to turn out! I was SO upset with the ending, and I don't get it at all! What happened? Why did he do that?? How are they cured?? I don't like how they leave the "normal, everyday" person totally confused at the end!! GOSH!