41.   The flu virus is airborne, which means it travels in tiny droplets in coughs and sneezes and can infect mucous membranes in the nose, eyes and mouth.

42.   The flu virus reproduces and leaves the body within days of infection, and it is genetically fragile and breaks down quickly after death.

43.   The going theory was that flu viruses might reassert more easily, and become more compatible with humans, if they mixed in an intermediate host like a pig.

44.   The new compound is a neuramindase inhibitor, meaning that it blocks an enzyme the flu virus needs to infect cells.

45.   The scientists said the compound, which interferes with the reproduction of the flu virus, will be ready to test in people in several months.

46.   The severity of flu varies from year to year depending on the particular strain of flu virus that is causing most cases.

47.   The territory had banned imports of chickens, ducks and geese from China, although it said there was no evidence that the flu virus had originated there.

48.   The vaccine is changed slightly each year to provide immunity against whatever flu viruses are expected to be circulating the globe.

49.   The UCLA researchers did not propose any immediate change in vaccination policy because of the greater risk posed by actual infection with the flu virus.

50.   The vaccine protected against both A and B strains of the flu virus.