The mysteries of the 1918 flu were beginning to be solved. There was a swine flu connection—probably people had given the flu to pigs, scientists proposed, and the virus may have remained in pigs, lying dormant until, one day, it might strike back at people. But there remained the question of when, and whether, the deadly flu virus might come back to infect the human race. And if it did, how could we get advance warning?
