#18,410
Over the past 6 months reporting of novel flu cases from Mainland China has dropped appreciably, with the last H5N6 case reported in July, and only 4 H9N2 cases reported between May and the end of October (see chart below).
Of course, a lack of reports doesn't always mean a lack of cases, since China often only belatedly reports novel flu cases. Sometimes this is because of delays in testing, and sometimes because it is politically expedient.
Today, Hong Kong's CHP has published a bare bones listing of 7 newly announced H9N2 cases, all of which occurred in just 3 weeks in Mainland China.
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.
Only about 140 cases have been officially reported over the past 20 years (see FluTrackers list), and most (but not all) of them have reported mild or moderate illness. Seroprevalence studies, however, suggest the infection is far more common than we believe.
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 co-conspirator (see Vet. Sci.: The Multifaceted Zoonotic Risk of H9N2 Avian Influenza).
Details are scant, and the significant of today's announcement is difficult to determine. It could be due to increased surveillance, or it might signify an increase in transmission.
We'll obviously be watching China closely for future reports.
Some earlier (2024) blogs on HPAI H9N2 include:
WHO DON: Avian Influenza A(H9N2) - Ghana
WHO: India Reports 2nd H9N2 Case
