#19,024
Although there is no mention of it in today's CHP Weekly Avian flu report, the WHO's WPRO (Western Pacific Region Office) latest avian flu report contains a brief description of 3 new H9N2 cases reported by China.
Human infection with avian influenza A(H9N2) virus
From 9 to 15 January 2026, three new cases of human infection with avian influenza A(H9N2) virus were reported to WHO in the Western Pacific Region. All three cases were reported from China: The first case is a five-year-old male from Hubei Province, with an onset of symptoms on 30 November 2025; the second case is an eight-year-old female from Jiangsu Province, with an onset date on 4 December 2025; the third case is a one-year-old male from Guangxi Province, with an onset date on 7 December 2025.
The first case had exposure to backyard poultry whereas the other two cases reported no known exposure to live poultry.The parents of the second case visited a store selling freshly slaughtered poultry, and the third case also had indirect exposure to freshly slaughtered poultry. All three cases have now recovered.
Since December 2015, a total of 155 cases of human infection with avian influenza A(H9N2), including two deaths (both with underlying conditions), have been reported to WHO in the Western Pacific Region. Of these, 152 were reported from China, two were from Cambodia, and one was from Viet Nam.
This comes on the heels of 7 cases reported by WHO in the 3rd week of December. The ECDC summarized those cases as:
The cases were reported in Guangdong (1), Guangxi (3), Henan (1) and Hubei (2) provinces with onset of symptoms in September, October and November 2025. Five patients were children and two were adults. Five of the seven individuals had mild disease, two elderly individuals were hospitalised, of whom one with underlying conditions was hospitalised with severe pneumonia. All but one had exposure to birds either in backyard poultry (4) or live poultry market (2). Investigations are ongoing for one case to determine the source of infection.
As we discussed last month, in HK CHP: Another Cryptic Announcement of H9N2 Cases From the Chinese Mainland, reports out of China are often belated, and many lack critical details.
And of course, the expectation is that most cases are never detected by surveillance, since most are believed mild, and testing (particularly of adults) in China usually only occurs in hospitalized patients.
While HPAI H5N1 remains firmly atop our pandemic concerns list - primarily due to its potential severity - the CDC's IRAT List contains 25 influenza A strains across 12 different subtypes (H1N1, H1N2, H3N2, H5N1, H5N2, H5N6, H5N8, H7N7, H7N8, H7N9, H9N2, H10N8).
Arguably, there are several more which could be added to this list, including H3N8, H6N1, and H10N3. Even among this narrow field of influenza A viruses, H5N1 ranks fairly far down the CDC's list (#7).
In terms of likelihood of emergence, the CDC currently ranks a Chinese EA H1N1 `G4' swine virus at the very top of their list of zoonotic influenza A viruses with pandemic potential, with 3 other North American swine variant viruses and H9N2 scoring above H5N1.
While H9N2 has a reputation of being a relatively mild viral infection - primarily reported in children - we've seen changes in its epidemiology of late; including more adult infections (some seriously ill) reported out of China.
H9N2 also easily reassorts with, and often enhances, other novel influenza viruses (including H7N9, H5N1, and H5N6), making it an important viral co-conspirator (see Vet. Sci.: The Multifaceted Zoonotic Risk of H9N2 Avian Influenza).
But, despite all of this,, LPAI H9N2 doesn't get a lot of respect.
Since it is a low-path virus in poultry, it is not considered `reportable' to WOAH, so surveillance is suboptimal. Some countries vaccinate poultry against it, but existing vaccines have not been very effective (see J. Virus Erad.: Ineffective Control Of LPAI H9N2 By Inactivated Poultry Vaccines - China), and that may have even helped drive its evolution.
Last October, in China CDC Weekly: Epidemiological and Genetic Characterization of Three H9N2 Viruses Causing Human Infections, we looked at a local CDC investigation into 3 pediatric cases which were reported last April from Changsha City, Hunan Province, China.
Their report found a number of indicators of increased mammalian adaptation within the virus, including an enhanced ability to infect upper respiratory (α2,6-sialic acid) tract receptors, and a number of HA protein mutations, including; H191N, A198V, Q226L, and Q234L.
Last November, in EM&I: Enhanced Replication of a Contemporary Avian Influenza A H9N2 Virus in Human Respiratory Organoids, we looked at a study which compared two H9N2 isolates (from 2024 and 1999) across several organoid models, and found today's virus to be far better adapted to human hosts.
In summary, we demonstrated that a recent H9N2 virus is more adapted to humans, and is able to replicate to high titres in both upper and lower human respiratory tract which may confer higher person-to-person transmissibility and virulence. Our study underscores the importance of human organoid-based phenotypic monitoring and inter/intrahost genotypic monitoring for assessing the zoonotic risk of avian influenza viruses.
These, and other recent studies (see here, here, and here) have elevated concerns over the trajectory of LPAI H9N2 viruses. While trying to predict the source of the next pandemic is a mug's game, H9N2 certainly deserves our attention.
