He's still getting closer. If he doesn't see any reason to retreat, he likely won't. Steve, he knows, has a lot of the answers he's been looking for.

"Yeah, but you're still sick." He crosses his arms, obstinate. "Whatever this is, it's gotta be strong if it's got you feelin' it." He knows that much. If he's anything along the lines of Steve's level of super-soldier, he knows exactly how much it takes to get him sick. (What he doesn't realize, of course, is that his own abilities have been limited here as well.)