Have you recently flown into the US from abroad? On the landing card it asks if you’ve been in contact with things should not be brought into the US.
Have you encountered agriculture or been on a farm?
Have you been exposed to people coughing ebola?
And then one slightly odd question that gets overlooked:
Are you carrying snails? (paraphrasing here)
This is because snails are actuallly really deadly. Or more specifically they are a vector for some really deadly parasites. Read about it, and how to control the snail/parasite spread over at Science Friday.