From what I understand, being a physician requires not just what you learn in medical school and residency, but continued education throughout your practicing years. I know many physicians that subscribe to different journals of medicine (and read them.) A few times, one doctor will ask a colleague next to him/her if they read the most recent study concerning X (normally something important and pertinent to that specialty, e.g. acute stroke management for EM).
While I'm guessing most pre-meds don't regularly read the New England Journal of Medicine, they should have at least a basic understanding of big current event/topics, such as Zika. I guess one rule of thumb someone could take is that if it's getting enough buzz to trend on Twitter or Facebook, it's something worth investing a Google search or two on it. It's similar to interviewers asking interviewees about their understanding/view point on the Affordable Care Act a few years ago.
Now, I want to be optimistic and say that this may not have been a fatal mistake, but IMO this will definitely be noted on your eval. There's nothing you can really do now, but be conscious of current health topics from now on, both for future interviews (if you have/need them) and your career.
