The designation of low or highly pathogenic avian influenza refers to the potential for these viruses to kill chickens. The designation of “low pathogenic” or “highly pathogenic” does not refer to how infectious the viruses may be to humans, other mammals, or other species of birds.
Most strains of avian influenza are not highly pathogenic and cause few signs of disease in infected wild birds. However, in poultry, some low pathogenic strains can mutate into highly pathogenic avian influenza strains that cause a contagious and severe illness among poultry and sometimes wild birds, and often death. The effect is dependent on the viral strain and host species.
Learn more: USGS Avian Influenza