You can have a virus where people feel well enough while they’re infectious that they get on a plane or they go to a market.
I can't understand a structure of this sentence. What do 'where' and 'that' do and how should I understand them?
It's from a TED video, 'The next outbreak? We’re not ready' in 4:20. https://youtu.be/6Af6b_wyiwI?t=260