11.   Another virus strain causes hemorrhaging and even death.

12.   Currently, the standard flu vaccine is altered every year to keep up with changing virus strains.

13.   It advises national health authorities and drug companies every February on the composition of the virus strains for the forthcoming season.

14.   Last fall, the vaccine was delayed because one virus strain was difficult to grow.

15.   No other incidents have been reported, and interviews with poultry workers indicated that humans have not been affected by the new virus strain, he said.

16.   Previous genetic research suggests human flu originated from a large pool of virus strains in wild bird populations, he said.

17.   Scientists world-wide have been noting with consternation that virus strains are growing more drug-resistant because of overuse of antibiotics.

18.   Scientists discovered the new virus strain in some bat colonies a few months ago while researching another rare disease, equine morbillivirus, which is also found in horses.

19.   Some virus strains need to latch onto those structures to infect cells, a necessary step before they can reproduce.

20.   The bad news is that new virus strains, resistant to the known medicine are beginning a resurgence.