#18,715
This week's avian influenza report from Hong Kong provides a cryptic list of 9 recent novel flu infections reported on the Mainland; including the 5th H10N3 case reported since 2020, and 8 additional H9N2 cases.
Today's announcement is the 5th H10N3 case reported from China since 2021.
- In June of 2021 China's NHC Reported the 1st Human H10N3 Avian Flu Infection - Jiangsu Province
- Followed in 2022 by A Cryptic Report of A 2nd H10N3 Case from Hong Kong's CHP.
- In April of 2023 a 3rd case was reported from Yunnan Province (see Nature Portfolio preprint)
- And in January of 2025, 1 New H10N3 Case was reported from Guangxi)
Today's case is once again from Guangxi.
Last July, in Frontiers: Phylogenetic and Mutational Analysis of H10N3 Avian Influenza A virus in China: Potential Threats to Human Health, we looked at a report that described 4 mutations of concern in the 2023 case (HA Q226L, PB2 D701N, PA S409N, and M2 S31N), along with the patient's treatment and course of illness.
Last July, in Frontiers: Phylogenetic and Mutational Analysis of H10N3 Avian Influenza A virus in China: Potential Threats to Human Health, we looked at a report that described 4 mutations of concern in the 2023 case (HA Q226L, PB2 D701N, PA S409N, and M2 S31N), along with the patient's treatment and course of illness.
Last December Vet. Microbiology: The novel H10N3 Avian Influenza Virus Acquired Airborne Transmission Among Chickens: An Increasing Threat to Public Health reported the virus has become better adapted to poultry, is highly pathogenic in mice, can be transmitted via respiratory droplets between guinea pigs, and can also be transmitted via the airborne route by chickens.
They also reported on a serology study of poultry workers, which found a small but significant (1.5%) positivity rate. We've also seen other H10 viruses spillover to humans in China, including H10N8 and H10N5. So far, we've seen no evidence of human-to-humans transmission.
Today's HK CHP report also lists 8 new H9N2 cases, 7 of which are children. Most H9N2 infections are mild, although several deaths have been reported. Details on the severity of illness of these cases is not provided, although no deaths are indicated.
Seroprevalence studies suggest that H9N2 is underreported around the globe (see FluTracker's list), but over the past five years we've seen a surge of cases reported from China (see ECDC Chart below), likely due to increased surveillance for COVID.
H9N2 is poorly controlled in Chinese poultry, despite the use of vaccines (see J. Virus Erad.: Ineffective Control Of LPAI H9N2 By Inactivated Poultry Vaccines - China), which has led to the creation and spread of numerous of genotypes.
H9N2 also 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).
H9N2 is such a versatile virus, it has even been detected in Egyptian Fruit bats (see Preprint: The Bat-borne Influenza A Virus H9N2 Exhibits a Set of Unexpected Pre-pandemic Features). Six weeks ago, in Cell: Early-warning Signals and the Role of H9N2 in the Spillover of Avian Influenza Viruses, we took a deep dive into the evolving threat from H9N2.
While LPAI H9N2 is admittedly not at the very top of our list of pandemic concerns, the CDC has 2 different lineages (A(H9N2) G1 and A(H9N2) Y280) on their short list of influenza viruses with zoonotic potential (see CDC IRAT SCORE), and several candidate vaccines have been developed.
Which is why continued reports of cases in China (and elsewhere) are worthy of our attention.
