#17,839
Yesterday's CHP weekly Avian Influenza Report Vol 19, #51 included the notification of 2 H9N2 cases (both from November) in Sichuan Province (see above chart), with the only other information being the gender and age of the patients.
The most recent ECDC/EFSA report (Dec 14th) showed 7 such cases reported in China in 2024, and China leading the world with 115 cases overall.
Today's cases follow 3 others reported from Sichuan Province in 2023, although it is likely that a lot of cases go unreported (see FluTrackers List). H9N2 infection is generally mild, and in most cases, patients are never tested for the virus.
Seroprevalence studies, however, suggest people with exposure to infected poultry often develop H9 antibodies.While 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.
As an LPAI (low path avian influenza), H9N2 is not considered a `reportable' disease by WOAH (formerly the OIE), even though it is zoonotic.
But H9N2's biggest threat may come from its unique ability to reassort with other, potentially more dangerous, avian viruses. Its internal genes have often been found inside many HPAI viruses (including H5N1, H5N6, H7N9, and most recently zoonotic H3N8) - (see The Lancet's Poultry carrying H9N2 act as incubators for novel human avian influenza viruses).
Control of H9N2 has proved difficult, as the virus continues to mutate, and many countries continue to employ outdated and ineffectual vaccines (see J. Virus Erad.: Ineffective Control Of LPAI H9N2 By Inactivated Poultry Vaccines - China), some of which may be driving its evolution.
Although most reported H9N2 infections are mild or moderate, in November of 2021 China reported a rare fatal outcome in a 39-year-old man from Qiandongnan Autonomous Prefecture, Guizhou Prefecture.
While H9N2 doesn't have the fearsome reputation of H5N6 or H7N9, it reassorts readily with other viruses and has shown an increasing ability to infect humans (and other mammals), making it very much worthy of our attention.
