21.   In order to survive, flu viruses change slightly year to year, requiring changes in the vaccine to protect against them.

22.   In the meantime, Taubenberger and his colleagues had found fragments of the flu virus in another of the pathology specimens that they had ordered from the warehouse.

23.   Internet business models, like the technologies that drive them, mutate faster than a flu virus.

24.   Is Tyson compared to Israeli commandos, bears, Islamic terrorists, IRS agents or flu viruses?

25.   It is working on conquering the flu virus.

26.   It was a rare daytime episode triggered, he said, by a flu virus.

27.   Japanese researchers have found a type of flu virus in Indian parakeets which could cause a serious outbreak in humans if it mutated.

28.   Kawaoka explained that bird flu viruses sometimes acquired changes in a protein, hemagglutinin, that the virus needed to burst into cells and infect them.

29.   Kim said the flu virus infected cells in its host, reproduced inside these cells and then broke out to spread the infection to other cells.

30.   Lacking immunity to flu viruses, children are most likely to acquire the virus, spread it among themselves and transmit it to others.