Burgers must be cooked all the way through to an internal temperature of 160 degrees to kill any potentially harmful bacteria.
For steaks, rare was OK, because any bacteria would be limited to the outside of the meat.
"Many companies are using needles or blades to tenderize the meat. What that can do is push pathogens from the outside inside the steak. That makes it more like a piece of ground beef in terms of the safety profile," says Sarah Klein of the Center for Science in the Public Interest.
The process does not leave any obvious marks, so you can't really tell whether a piece of meat has been mechanically tenderized.
And right now, federal rules do not require this information to be on the label.
"That means that you have to cook all steak well done, as if it's ground beef, just like you would a burger," says Klein. "That means you cook it to 160 degrees internal temperature."
The USDA has proposed a rule that would require companies to disclose whether their cuts of beef have been mechanically tenderized, and to provide instructions on proper cooking. That rule could be in place by next year.
Has your steak been mechanically tenderized?
Needle-Tenderized Steaks to Require New Labels in U.S.