41.   People become infected by guinea worm when they drink water containing microscopic larvae of the parasite.

42.   People become infected with the virus by coming into contact with rodent droppings or inhaling dust that has been contaminated with rodent urine.

43.   Other government officials said that the germ spores were finely milled and could have easily spread through the air to infect many people.

44.   People become infected by inhaling spores of the fungus, which can be found living in the soil or blowing in the desert air.

45.   People can become infected by inhaling anthrax spores, by eating contaminated meat, or if spores come in contact with skin.

46.   People get infected most commonly through mosquito bites.

47.   Public health officials are predicting flu to strike four weeks earlier than usual because of a strain that infected people on Alaskan cruise ships the past two summers.

48.   Q. Could enough anthrax leak out of a sealed envelope to infect several people?

49.   Scientists guess that the mail contamination was slight, with too few spores to infect most people.

50.   Scores of tests will be needed before health officials are sure whether the people stricken were infected by some type of West Nile viruslike illness or St. Louis encephalitis.