31.   Officials call it a necessary precaution even though the disease has not affected humans.

32.   Officials said the moves were purely precautions against mad cow, which has been linked to a variant strand of Creutzfeldt-Jakob disease, which affects humans.

33.   Scientists have linked mad cow disease to variant Creutzfeldt-Jakob disease, which affects humans.

34.   Studying fragile life in the tidal area of a seashore, he said, could provide an advance warning of changes that might affect humans more dramatically.

35.   The animal virus, which spreads among cloven-hoofed animals such as cows and pigs, does not affect humans.

36.   That outbreak did not affect humans.

37.   The college student said she volunteered for the study, designed to monitor how particulate matter affects humans, because she is convinced such research benefits society at large.

38.   The bug is not known to affect humans, but it does take its toll on plants.

39.   The beef export ban followed an announcement of a possible link between that disease in cattle, and a fatal brain ailment affecting humans.

40.   The disease does not affect humans.