I think it is just from eating the meat. That is why all those FDA warnings are out there about safe meat handling, and COOKING thorougly!
People that like beef rare or medium rare gross me out (no offense). DH used to work on a Dairy Farm, and some of those cows would be butchered. My DH said, don't eat the meat. And I never did!
I know they say beef in a steak form is safe to eat still mooing in the middle, but you won't find it mooing at my house! Well done to burnt, thank you very much!
edited for typos. too early yet.