#19,409
As of today's report, Hong Kong's CHP has reported a total of 23 H9N2 cases over the past 6 months, with 6 of those reported by the CHP since October 19th. As you can see by the dates in the above graphic, there continue to be substantial delays in reporting, with 5 of the 6 cases reported occuring in September.
Four of the six cases are in children (who are more likely to be screened for the virus), while two are in elderly adults.
While H9N2 infection is typically mild or moderate, some patients are hospitalized, and a few deaths have been reported. The two most recent cases - announced today - were previously reported on in the WHO WPRO weekly avian flu report released on October 28th.
Human infection with avian influenza A(H9N2) virus
From 23 to 29 October 2026, two new cases of human infection with avian influenza A(H9N2) virus were reported to WHO in the Western Pacific Region, both from China. Both cases were paediatric patients, one from Liaoning Province, with symptom onset on 20 September 2026, and one from Guangxi Zhuang Autonomous Region, with symptom onset on 13 October 2026. Both cases had exposure to poultry. All close contacts of both cases tested negative for influenza A. Both cases had fully recovered at the time of reporting.
Since 2015, a total of 189 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,186 were reported from China, two were from Cambodia, and one was from Viet Nam.
Most human infections with avian influenza A(H9N2) have been associated with exposure to infected poultry or contaminated poultry environments, and the majority of cases have been mild. Sporadic human infections continue to be expected in areas where H9N2 viruses circulate in poultry populations. Current evidence indicates that H9N2 viruses have not acquired the ability for sustained human-to-human transmission, and the risk of further community-level spread remains low.
Last August, in WHO Influenza at the human-animal interface (Aug 7th) - Uptick in H9N2 Cases in China, we looked at this recent increase in reported cases. Whether this is due to more frequent spillovers, or better surveillance, isn't known.
Despite being clearly zoonotic - LPAI H9N2 is considered a `non-reportable' disease in poultry or wild birds by WOAH (see Terrestrial Animal Code). Complicating matters, China's attempts to control LPAI H9N2 through vaccines have been less than successful.
Several recent Chinese studies have found signs that LPAI H9N2 is becoming better adapted to mammals, warning of its pandemic potential; including:
- In early August, in EM&I: Genetic evolution, phylodynamics, geographic spread of H9N2 avian influenza viruses in China from 2014 to 2025: an increasing potential zoonotic risk, we saw yet another Chinese study warning that H9N2 was accruing mammalian adaptations which increases its zoonotic risk.
- Five months ago, in Viruses: Epidemiological and Virological Characteristics of H9N2 Avian Influenza Virus in Jiangsu Province, China, 2024, researchers warned that that Jiangsu’s circulating H9N2 viruses have acquired human receptor preference and mammalian adaptation, posing silent infection and pandemic risks
- In October 2025, in China CDC Weekly: Epidemiological and Genetic Characterization of Three H9N2 Viruses Causing Human Infections, investigators reported 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.
- The Asian Y280/G57 lineages have shown increasing signs of mammalian adaptation (see EM&I: Enhanced Replication of a Contemporary Avian Influenza A H9N2 Virus in Human Respiratory Organoids)), while the African and Middle Eastern Lineages (mostly European G1-like) are older and less evolved.
- In the summer of 2025, in Nature: Genetic diversity of H9N2 avian influenza viruses in poultry across China and implications for zoonotic transmission, researchers reported rising prevalence of key mutations associated with increased infectivity and pathogenicity in mammals.
While H9N2 doesn't garner the kind of headlines that H5N1 gets, our own CDC lists two lineages (A(H9N2) G1 and A(H9N2) Y280) as having at least some pandemic potential, and several candidate vaccines have been developed.
So we watch these developments with more than just academic interest.
