21.   Two of the three flu strains in the vaccine had also proven difficult to grow.

22.   What most mystifies health officials is why the bird flu strain appeared in humans now and precisely how it is being transmitted to humans.

23.   With good vaccines against whatever the projected flu strain is each year, flu is not the threat it once was.

24.   A drug inhaled once a day proved effective in helping to prevent two common flu strains, researchers reported Wednesday in the Journal of the American Medical Association.

25.   A new and unexpected flu strain could make the coming weeks a lot harder on the elderly and chronically ill, the U.S. government said.

26.   After all, new flu strains come from pigs and AIDS is believed to have jumped from monkeys to man.

27.   Because different flu strains circle the globe each year, a new flu vaccine must be brewed annually.

28.   Because different flu strains emerge each year, a new flu vaccine must be brewed annually.

29.   Flu virus genes are highly changeable, and slightly altered flu strains appear almost annually.

30.   Four of the five dead were children, as are many of those stricken with the unusually aggressive flu strain, said Health Ministry spokeswoman Irina Slobodeniuk.