Birds without natural immunity that migrate or roost together in large flocks, such as geese, are most likely to die in large numbers. A recent bird flu outbreak among migratory eared grebes in Utah killed between 15,000 and 25,000 birds near Great Salt Lake, state wildlife officials said in early February.

An H5N1 infection can be fatal for domestic animals, but there are steps you can take to minimize the risk of them catching the virus.