Lack of bird flu testing may be hiding true spread of virus on US farms

H5N1 has been found in commercially available milk - but gaps in testing of cattle and humans are hampering effort to stop virus

Serious gaps in testing animals and people could be obscuring the true rate of avian influenza cases in the US and make it difficult to understand how the H5N1 virus is spreading - and how to stop it, experts say.

Facing reluctance from farms to test workers and animals, scientists are now turning to experimental studies to understand how H5N1, a highly pathogenic bird flu, is spreading through cows and on to other farms.