Credit CDC
#17,846
Ten years ago this month, South Korea - which had battled HPAI H5N1 off and on for a decade - was hit by a new HPAI H5N8 clade 2.3.4.4 virus, which tore through their poultry industry. Prior to that, similar H5N8 viruses had only been (rarely) seen in wild birds (in 2010) in Asia, and isolated in 2 ducks in Zhejiang Province in 2013.
At roughly the same time, a deadlier (in humans) HPAI H5N6 clade 2.3.4.4 virus emerged in Sichuan China, and after a slow start, has now infected nearly 90 people across much of China (see map below).
Over time these clade 2.3.4.4 viruses have evolved into into numerous subclades (a-h), scores of genotypes, and even spun off new subtypes (including the now globally dominant HPAI H5N1 clade 2.3.4.4b).
This convoluted evolutionary process means that we can have multiple viruses with the same subtype (e.g. H5N1 or H5N6) and clade (e.g. 2.3.4.4), but with very different threat profiles. Some H5N6 viruses, for example, may pose a much bigger threat to human health than others.
H5N8 became the dominant HPAI H5 virus across much of the world in the middle of the last decade, but gave way (briefly) to H5N6 in 2018, and was later overwhelmed by a much more transmissible HPAI H5N1 clade 2.3.4.4b virus in 2021.
But, influenza's super power is its ability to continually change via reassortment and antigenic drift.
Which explains why, after an absence of nearly 6 years, South Korea (and Japan) have reported the return of HPAI H5N6 over the past 30 days.
South Korea originally reported 8 outbreaks in domestic poultry, and 3 in wild birds. Today, in updates to both reports, we learn than 10 more poultry farms have been infected, and 1 more wild bird has tested positive for HPAI H5N6.
Thus far, we've seen no indication that this HPAI H5N6 virus poses any greater risk (to poultry or humans) than its HPAI H5N1 cousin. It's recent return and rapid spread, however, are being closely watched.
South Korea's MAFRA (Ministry of Agriculture) released the following (translated) statement on this increased avian flu activity in December.
Minister of Agriculture, Food and Rural Affairs takes care of the field as the new year begins
2024.01.01 16:00:00 Quarantine Policy Bureau Avian Influenza Quarantine Division
Minister of Agriculture, Food and Rural Affairs Song Mi-ryeong visited a highly pathogenic avian influenza quarantine site on Monday , January 1 , as her first on-site visit after taking office . Minister Song Mi-ryeong confirmed the operation status of the base disinfection facility located in Jangsu-gun, Jeollabuk-do , inspected the livestock quarantine response posture in the Jeollabuk-do region at the Jeollabuk-do Animal Hygiene Testing Laboratory, and encouraged quarantine officials .
This year, since the first outbreak of highly pathogenic avian influenza at a broiler duck farm in Goheung, Jeollanam-do on December 3 , there have been 25 cases * as of December 31 , 2023. The outbreak occurred somewhat later than last year ** , but there were two serotypes (H5N1 type) . , H5N6 type ) occurring simultaneously , the risk of further spread is high .
* Occurrence status by city and province in 2023 : 18 cases in Jeonbuk , 6 cases in Jeonnam , 1 case in Chungnam
** First outbreak status in 2022 : '22.10.17., Yecheon Duck Farm, Gyeongsangbuk-do
Minister Song Mi-ryeong visited the Jangsu-gun base disinfection facility and said that livestock infectious diseases are mainly spread through people and vehicles, so the role of the base disinfection facility is very important, and visited the facility to manage the facility and ensure that there are no disruptions in the operation of the disinfection facility due to freezing, etc., even in winter when temperatures drop below freezing. It was emphasized that vehicles should be thoroughly disinfected .
Then, we will go to the Jeollabuk-do Animal Hygiene Testing Laboratory, which is in charge of diagnosis, surveillance, and research for livestock infectious diseases . Since quick and accurate diagnosis is important to minimize damage from livestock infectious diseases, we will do our best to establish a 24- hour response system and respond quickly. requested .
Minister Song Mi-ryeong told the attending officials, “ This year’s top priority is to minimize the occurrence and spread of highly pathogenic avian influenza by implementing strengthened quarantine measures for laying hen clusters and large-scale laying hen farms in order to stabilize egg prices, which are closely related to people’s lives.” He requested that “everyone cooperate and respond with one mind . ”
In addition , in the future , as the risk of livestock infectious diseases is increasing due to climate change and active overseas exchange, the quarantine responsibility of poultry affiliates will be strengthened and cooperation with the private sector , such as livestock disease inspection through private institutions and disinfection and pest control using specialized companies, etc. “ We plan to continue to expand collaboration , ” he said .
Lastly , in order to prevent the occurrence and spread of highly pathogenic avian influenza, he emphasized that “ livestock farms and livestock personnel must strictly comply with basic quarantine rules, such as 2- stage disinfection of vehicles entering and exiting the barn, wearing quarantine clothing and changing boots in the livestock barn , ” and “ General He urged the public to participate in the prevention of infectious livestock diseases by refraining from entering migratory bird habitats and poultry farms .
Whether this is just a temporary incursion - like we saw in 2018/2019 - or the emergence of a competitive subtype for H5N1 (like happened with H5N8 in 2014), remains to be seen.
Stay tuned.
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