Small flocks of backyard poultry, specifically those chickens that have plenty of access to the outdoors where they are in the sun and wind, are the least likely to contract bird flu. The virus does not survive when it becomes dehydrated.
Wild birds have the H5 virus all the time, especially waterfowl. Of the wild birds tested in the US and Canada last summer about 3% of them showed H5.
What does that mean to us? Don't use pond water where wild waterfowl poop as a supply for your poultry. Use a water supply that is fit for human consumption. Seriously the one outbreak of H5N7 we had here in Canada traced back to a farm where the city water supply was low so they doubled the commercial price, the farmer could not pay it so he got a pump and used the water on his property. It worked fine for over a year then some migratory waterfowl stopped by for a rest and his layer hens got sick.