William Schaffner, M.D., Vanderbilt University
Question: My friends have just returned from a trip out of state. How long does it take for swine flu symptoms to show?
Answer: Well you know, it's very interesting that you mention out of state, because this swine flu virus is now in every state, but given your question, it usually takes 48-72 hours after you've been exposed to the virus for you to become sick, and so that's what we call the incubation period.
