Pigs in Canada may be first in recent outbreak to test positive for virus . One - third of 160 sick Americans visited Mexico or had contact with Mexico . WHO reports 37 confirmed cases of H1N1 infection in 15 countries .
Pigs in Canada may be first in recent outbreak to test positive for virus . One-third of 160 sick Americans visited Mexico or had contact with visitor . WHO reports 787 confirmed cases of H1N1 virus in 17 countries .