Since a spillover in October 2023 the novel reassortment has replaced the older clade in Cambodia's poultry.
The new UK mpox patient is another member of the index case's household.
In related developments, the USDA reported more dairy cow and poultry outbreaks, as Los Angeles Country announced its first H5 wastewater detection.
In other developments, California reported a few more poultry culler illnesses, along with more outbreaks in both dairy cows and commercial poultry.
The pig didn't have symptoms, and further examination is under way to fully assess if infection occurred.
So far 15 of the human cases have been associated with exposure to H5N1-infected poultry, and 20 have been associated with exposure to sick or infected dairy cows.
In other developments, tests confirmed more human infections, outbreaks in California cows, and events in poultry in 3 western states.
As health officials brace for more cases in farm workers, Utah ag officials are moving quickly to monitor dairy cattle near a large outbreak at a layer farm.
In other developments, Quest Diagnostics will introduce an H5 molecular test by the end of the month, which should increase testing capacity.
The spurt of infections in Washington state is reminiscent of what Colorado experienced over the summer with illnesses in poultry cullers.
