This is a TV series from the early 2000s (maybe the late 90s). It was on prime time TV in the US.

There is a government agency that has a time machine that allows the main character to jump back in time a day or a week - I can't remember exactly, but it couldn't send you very far back in time.

I recall one episode where a terrorist releases some sort of virus from a lab that kills lots of people, including someone important (maybe the President?). The first symptom is a bloody nose. The hero has to go back over and over to stop the outbreak, each time getting closer and closer to the culprit before he breaks the vial that contains the virus. When he finally succeeds, he is the only one infected, but they immediately quarantine him and give him treatment.