separate

Dear Fail,

Yesterday I was at a party and I had to make hamburgers. Today I got calls from my friends saying that they got sick, and that they think it was from the food. So I was wondering if it were possible that it was from my. Heres what I did. I cut up hamburger meat on the cutting board. Then I put the raw meat on a plate, and took it outside. Once they were done cooking I put them back on the plate to take inside. Then everybody wanted toppings, so I cut up some lettuce and tomatoes using the cutting board. Any ideas that it could be from my food?