The scientist checked his records. The sample came from a Holstein, a black and white dairy cow. She lived in Canada for most of her life. That's probably where she got infected. But no one noticed, and she was later sold to a ranch in Washington State.
After the cow was killed, she was cut up. Then various parts of her body were sent to factories in three western states.
Now Hughes knew what he was looking for–and where to start.
—When Birds Get Flu and Cows Go Mad! How Safe Are We?, John DiConsiglio
What are the signal words that point to a solution in this passage?
probably . . . But
later . . . in
After . . . was
Now . . . and