Latest data shows which counties have been hardest hit by bird flu outbreaks among poultry flocks as the human case count climbs.

The newly reported H5N9 strain was found Monday at a duck farm in Merced County, California, according to the World Organization for Animal Health. The Paris-based organization that studies animal diseases said it's the first verified U.S. case of H5N9 in poultry. The organization said the more common strain H5N1 was also found.

Most of the UK has been placed under an avian influenza prevention zone after cases show no sign of stopping. The new zone to tackle a rising number of bird flu cases was declared in England and Scotland after the spread among poultry has escalated.