51.   There was nothing unusual about the amino acids at that position in the Spanish flu virus.

52.   They are looking for clues to why that contagion was so much more virulent and lethal than any flu virus before or since.

53.   This is the hemagglutinin gene, which directs the production of proteins that enable the flu virus to attach itself to a cell in the respiratory system.

54.   Though work will go on for years, analysis has already provided vital new knowledge about flu viruses.

55.   To scientists trying to find out why some flu viruses are so much more virulent than others, this is an exciting discovery.

56.   Trying to avoid exposure to flu viruses would require a form of hibernation for the next four or five months.

57.   Two prescription drugs, amantadine and rimantadine, are on the market, though they are effective against only one strain of the flu virus.

58.   When the flu virus is found at a live market, the market is temporarily closed down.

59.   While most human flu viruses do not make mice ill, these strains generally affected mice and people in the same way.

60.   A Catholic church spokesman said Friday the deaths had been reported in Western Sepik province, and were thought to have been caused by a flu virus.