"I totally don't have COVID-19" (wink, wink)
Everyone is on edge flying during COVID-19. There are many shared surfaces, crowds that congregate in security, and plenty of times when social distancing just doesn't happen. TSA agents have essential jobs, and they're putting themselves at risk to keep travelers safe; in fact, reports the Washington Post, more than 1,000 have tested positive for COVID as of early July. So, you really don't want to strike fear into them by suggesting you have COVID-19, even if it's just a joke. (It's not funny.) This is also one of the things you should never say to flight attendants, who have been trained to take this matter seriously and could even boot you from your flight if there's a question as to whether you're actually infected. Masks are required throughout many airports, and while a TSA agent may ask you to pull yours down to confirm your identity, you should keep it secure at all other times.
13 Things to Never Say to TSA Agents, Source:https://www.rd.com/list/things-to-never-say-to-tsa-agents/