#17,312
With thanks and a hat-tip to Jurre Y Siegers, PhD @jurreysi on twitter, we have an announcement from the Cambodian CDC indicating that the cluster of H5N1 cases reported this week have been analysed, and found to be from the Asian clade 2.3.2.1c - not from the 2.3.4.4b clade which is currently circulating across most of the world.
This is obviously good news for those in Europe and the Western Hemisphere, who are currently dealing with a different H5N1 virus.
In addition to 2.3.4.4b, the WHO has identified 3 other clades of H5N1 circulating around the globe over the past 6 months:
- Clade 2.3.2.1a viruses were detected in poultry in Bangladesh. There were up to 10 amino acid substitutions in the HA of recent viruses compared to the HA of A/duck/Bangladesh/17D1012/2018, from which a CVV has been developed. Some of the recent viruses did not react well to a post-infection ferret antiserum raised against the A/duck/Bangladesh/17D1012/2018 CVV but instead reacted well with a post-infection ferret antiserum raised against the A/duck/Bangladesh/19097/2013 CVV.
- Clade 2.3.2.1c viruses were detected in birds in Viet Nam and Lao People’s Democratic Republic. Viruses from Viet Nam reacted well with a post-infection ferret antiserum raised against the A/duck/Vietnam/NCVD1584/2012 CVV, despite recent strains having up to 9 amino acid substitutions in the HA.
- Clade 2.3.2.1e viruses were detected in Timor-Leste. The HAs of these viruses were most closely related to viruses previously detected in Indonesia. There are no CVVs representative of this HA clade and the viruses from Timor-Leste reacted poorly with post-infection ferret antisera raised against clade 2.3.2.1a and 2.3.2.1c CVVs. No human infections have been associated with viruses of this clade and the extent of their circulation is uncertain.
This brief announcement from the Cambodian CDC Facebook page:
នាយកដ្ឋានប្រយុទ្ធនឹងជំងឺឆ្លង CDC
Currently, February 26, 2020Bird flu virus H5N1, which is the cause of death of girls living in Rolang village, Khlach commune, Central Sitha district, is a virus that has been studied among local birds, wild birds in Cambodia during the last few years.Bird flu H5N1 (clade 2.3.2.1c): Different from H5N1 bird flu in other countries around the world. Monitoring of the disease is ongoing, while the population in contact with the patient remains monitored.As of today, there has not been any clear evidence of transmitting H5N1 bird flu from person to person. Request all citizens to avoid direct harm with sick or dead birds. Let's protect and prevent together for our health.For more information, please contact phone number 118
Although we've not heard much about this clade over the past few years, 2.3.2.1c is a familiar foe. It is descendant from a clade (2.3.2) which emerged in 2009 in migratory birds in China, and is notable for producing severe - and often neurological - symptoms.
In January of 2015 we saw another large die off of birds in China (see H5N1 Detected In Swan Die Off In Henan Province) which was subsequently identified as clade 2.3.2.1c (see Novel H5N1 Reassortment Detected In Migratory Birds - China).
A few months later we learned that the H5N1 virus that reappeared in West Africa in late 2014 after a seven year absence was also clade 2.3.2.1c (see EID Journal: H5N1 In Nigerian Poultry – 2015).
This suggests that the novel Sanmenxia Clade 2.3.2.1c-like H5N1 viruses possesses tropism for the nervous system in several mammal species, and could pose a significant threat to humans if these viruses develop the ability to bind human-type receptors more effectively.
While today's announcement is a bit of a relief for much of the world, it is a reminder that HPAI H5 is a multi-faceted threat, and that it is fully capable of producing surprises going forward.
