Now he's infecting two groups — people with low antibody levels and those with high levels. Some were recently vaccinated, and some weren't. He'll compare how sick they get, how long they're contagious and how the immune system jumps into action.
Called a human challenge study, this kind of research hasn't been performed with flu viruses in the U.S. for more than a decade, before scientists had ways as sophisticated to measure what happens.
"It's all going to add up to a better understanding of what you need to have to be protected against the flu," said Dr. John Treanor, a flu specialist at the University of Rochester Medical Center who is closely watching the work.
So far, Memoli's patients are becoming contagious a day or two before they start feeling bad, one reason the flu spreads so easily. He sees a range of symptoms, from sniffles to a few days of moderate fever, fatigue and congestion.
Bennett's flu was pretty mild, and he passed the time studying, watching TV and playing games with the four other study participants infected this month.
"All I had to do was read and watch movies, so it wasn't that terrible," Bennett said. "It was a really cool experience" to see how research is done.