<P> The H1N1 form of swine flu is one of the descendants of the strain that caused the 1918 flu pandemic . As well as persisting in pigs , the descendants of the 1918 virus have also circulated in humans through the 20th century , contributing to the normal seasonal epidemics of influenza . However , direct transmission from pigs to humans is rare , with only 12 recorded cases in the U.S. since 2005 . Nevertheless , the retention of influenza strains in pigs after these strains have disappeared from the human population might make pigs a reservoir where influenza viruses could persist , later emerging to reinfect humans once human immunity to these strains has waned . </P>
<P> The H1N1 form of swine flu is one of the descendants of the strain that caused the 1918 flu pandemic . As well as persisting in pigs , the descendants of the 1918 virus have also circulated in humans through the 20th century , contributing to the normal seasonal epidemics of influenza . However , direct transmission from pigs to humans is rare , with only 12 recorded cases in the U.S. since 2005 . Nevertheless , the retention of influenza strains in pigs after these strains have disappeared from the human population might make pigs a reservoir where influenza viruses could persist , later emerging to reinfect humans once human immunity to these strains has waned . </P>
which of the animal is a carrier of h1n1
which of the animal is a carrier of h1n1
pigs
pigs