Michael Coston
Editor, Senior Moderator
South Korea: H5N9 Rising
#19,065
Last last year, South Korea's MAFRA Reported Increased Infectivity & Pathogenicity of This Year's Avian Flu Strains, which - for the first time - included 3 HPAI strains (H5N1, H5N6, and H5N9).
Of particular concern, their Animal and Plant Quarantine Agency conducted an evaluation of the infectivity and pathogenicity of the highly pathogenic avian influenza virus ( serotype H5N1) and found that the infectivity was more than 10 times higher than in previous years .
While we've been watching subtypes other than H5N1 (H5N6 & H5N5 in particular) around the world, HPAI H5N9 has been comparatively rare.
In early February, however, South Korea reported 3 poultry farm outbreaks (starting in Dec 2025) to WOAH resulting in the culling/loss of 150K birds.
On February 11th , MAFRA warned:
The virus that occurred in domestic poultry farms this winter has a higher infectious power than in previous years, and in particular , in the case of the H5N9 type, symptoms such as death are not obvious in ducks , so the risk of transmission is higher than ever , so local governments, related organizations , and poultry farms across the country must thoroughly implement quarantine measures,
Yesterday Hong Kong announced the suspension of imports of poultry meat and products (including poultry eggs) from Boryeong-si of Chungcheongnam-do Province in Korea due to a WOAH notification of an H5N9 outbreak, although it isn't clear if this is a new outbreak, or refers to the two from Dec/Jan.
Either way, this appears to be the first sustained spread of HPAI H5N9 in poultry reported anywhere in the world.
Today, and for the 2nd time in 3 days, South Korea has ordered a 24-hour halt in the movement of live poultry. as new outbreaks of (unspecified) HPAI H5 continue to mount.
South Korea is also dealing with FMD, and a rapidly escalating outbreak of ASF (African Swine Fever), which appears to be due to the sale and use of contaminated pig feed.
It's a lot to contend with, even for a country like South Korea.
The spring northbound bird migration begins in early March in South Korea, and runs through May, meaning avian flu activity could easily persist for several more months on the Korean peninsula.
While there are no known human infections with HPAI H5N9, we've seen human infection by other H5 subtypes; including H5N1, H5N2, H5N5, and H5N6 HPAI viruses.
Since we've also seen novel flu viruses with an N9 neuraminidase spillover to humans (China's H7N9 virus 2013-2019), there is little reason to believe it would present much of a barrier for H5 viruses.
The $64 question is whether this outbreak of H5N9 in South Korea virus is a flash in the pan, or if it has `legs'.
In 2016's Sci Repts.: Southward Autumn Migration Of Waterfowl Facilitates Transmission Of HPAI H5N1, we looked at a study which found that the flu viruses migratory birds encounter as they fly north in the spring often thrive - or reassort - in their summer high latitude roosting areas, and then are redistributed via the migratory flyways the following fall.
This is likely how South Korea's disastrous January 2014 H5N8 outbreak made it to the United States and Europe in less than a year, and became globally dominant by 2016.
A reminder that whatever avian viruses that may emerge South Korea - or any other country - assuming they are biologically `fit' enough, are unlikely to stay put for very long.
https://afludiary.blogspot.com/2026/02/south-korea-h5n9-rising.html
#19,065
Last last year, South Korea's MAFRA Reported Increased Infectivity & Pathogenicity of This Year's Avian Flu Strains, which - for the first time - included 3 HPAI strains (H5N1, H5N6, and H5N9).
Of particular concern, their Animal and Plant Quarantine Agency conducted an evaluation of the infectivity and pathogenicity of the highly pathogenic avian influenza virus ( serotype H5N1) and found that the infectivity was more than 10 times higher than in previous years .
While we've been watching subtypes other than H5N1 (H5N6 & H5N5 in particular) around the world, HPAI H5N9 has been comparatively rare.
- A little over a year ago, California Reported a New H5N9 Reassortant In Ducks, but that appears to have been a one-off event.
- Last May, the Philippines DOA Reports Their 1st Detection of HPAI H5N9
In early February, however, South Korea reported 3 poultry farm outbreaks (starting in Dec 2025) to WOAH resulting in the culling/loss of 150K birds.
- ob_181082 - Donggok-ri, Dasi-myeon, Naju-si, Jeollanam-do, Republic of Korea
- ob_181085 - Omani-gil, Cheonbuk-myeon, Boryeong-si, Chungcheongnam-do, 33403, Republic of Korea
- ob_181080 - Jinjuk-ri, Cheongso-myeon, Boryeong-si, Chungcheongnam-do, Republic of Korea
On February 11th , MAFRA warned:
The virus that occurred in domestic poultry farms this winter has a higher infectious power than in previous years, and in particular , in the case of the H5N9 type, symptoms such as death are not obvious in ducks , so the risk of transmission is higher than ever , so local governments, related organizations , and poultry farms across the country must thoroughly implement quarantine measures,
Yesterday Hong Kong announced the suspension of imports of poultry meat and products (including poultry eggs) from Boryeong-si of Chungcheongnam-do Province in Korea due to a WOAH notification of an H5N9 outbreak, although it isn't clear if this is a new outbreak, or refers to the two from Dec/Jan.
Either way, this appears to be the first sustained spread of HPAI H5N9 in poultry reported anywhere in the world.
Today, and for the 2nd time in 3 days, South Korea has ordered a 24-hour halt in the movement of live poultry. as new outbreaks of (unspecified) HPAI H5 continue to mount.
South Korea is also dealing with FMD, and a rapidly escalating outbreak of ASF (African Swine Fever), which appears to be due to the sale and use of contaminated pig feed.
It's a lot to contend with, even for a country like South Korea.
The spring northbound bird migration begins in early March in South Korea, and runs through May, meaning avian flu activity could easily persist for several more months on the Korean peninsula.
The mild (or subclinical) spread of H5N9 in ducks is particularly problematic, as detection and eradication will be difficult. Long term infection could produce even more reassortants.
While there are no known human infections with HPAI H5N9, we've seen human infection by other H5 subtypes; including H5N1, H5N2, H5N5, and H5N6 HPAI viruses.
Since we've also seen novel flu viruses with an N9 neuraminidase spillover to humans (China's H7N9 virus 2013-2019), there is little reason to believe it would present much of a barrier for H5 viruses.
The $64 question is whether this outbreak of H5N9 in South Korea virus is a flash in the pan, or if it has `legs'.
In 2016's Sci Repts.: Southward Autumn Migration Of Waterfowl Facilitates Transmission Of HPAI H5N1, we looked at a study which found that the flu viruses migratory birds encounter as they fly north in the spring often thrive - or reassort - in their summer high latitude roosting areas, and then are redistributed via the migratory flyways the following fall.
This is likely how South Korea's disastrous January 2014 H5N8 outbreak made it to the United States and Europe in less than a year, and became globally dominant by 2016.
A reminder that whatever avian viruses that may emerge South Korea - or any other country - assuming they are biologically `fit' enough, are unlikely to stay put for very long.
https://afludiary.blogspot.com/2026/02/south-korea-h5n9-rising.html