On Food and Cooking

animal by-products (feathers, viscera) as feed
for the next generation of animals, and
crowding the animals together in very close
confinement, both of which favor the spread
of the bacteria. Salmonella often have no
obvious effect on the animal carriers, but in
humans can cause diarrhea and chronic
infection in other parts of the body.
Escherichia coli is the collective name for
many related strains of bacteria that are
normal residents of the intestines of warm-
blooded animals, including humans. But
several strains are aliens, and if ingested will
invade the cells of the digestive tract and
cause illness. The most notorious E. coli, and
the most dangerous, is a special strain called
O157:H7 that causes bloody diarrhea and
sometimes kidney failure, especially in
children. In the United States, about a third of
people diagnosed with E. coli O157:H7 need
to be hospitalized, and about 5% die. E. coli
O157:H7 is harbored in cattle, especially