Just as you thought the drama related to bird flu died down, a new strain has been reported in California.

The H5N9 strain of bird flu is a newly emergent and rare subtype of avian influenza virus that has recently been detected for the first time in the United States. This highly pathogenic avian influenza (HPIA) strain was identified on a duck farm in Merced County, alongside the more common H5N1 strain (which is the one we have been covering for the past 2 years).

This is the first confirmed case of HPAI H5N9 in poultry in the United States,” the US Department of Agriculture said in a report to the World Organisation for Animal Health (WOAH) on Monday.

The positive test at the Merced County farm has led to “comprehensive epidemiological investigations and enhanced surveillance,” the government report noted.

H5N9 is a rare form of the common H5N1 bird flu, which has recently spread aggressively around the US, leading to the culling of hundreds of millions of poultry.