Range Of Endemic H9N2 Viruses (from
A Global Perspective on H9N2 Avian Influenza Virus)
#15,939
This morning Hong Kong's CHP reported mainland China's 12th H9N2 infection of 2021 (see below), involving a 30 y.o. woman from Guangdong province with onset on April 20th. Additionally, Cambodia reported a case - also in April - involving a 3 year-old boy.
The following update comes from the WHO Western Pacific Regional Office (WPRO):
Human infection with avian influenza A(H9N2) virus
Between 23 April and 29 April 2021, there was one new case of human infection with avian influenza A(H9N2) reported from the National Health Commission of the People’s Republic of China to WHO in the Western Pacific Region. The case is a 30-year-old female from Huizhou, Guangdong Province. The case had onset of mild symptoms on 20 April 2021.
To date, 12 cases of avian influenza A(H9N2) have been reported from China in 2021, and a total of 54 cases of human infection with avian influenza A(H9N2) have been reported in the Western Pacific Region since December 2015.
Admittedly, the numbers we have - as elevated as they may be of late - are believed to be significant undercounts. Most people in China (or elsewhere) who get minor-to-moderate flu-like symptoms never bother to see a doctor, or get tested.
We've covered the growing risks from the avian H9N2 virus numerous times over the years, not only as a standalone virus (see Viruses: Characterization of the H9N2 Avian Influenza Viruses Currently Circulating in South China ), but also for its ability to reassort with other - potentially more dangerous - influenza subtypes (see Viruses: PA From Recent H9N2 AIV Enhances H5N1 Infection In Mammalian Systems).Serological studies suggest human infection is far more common than those numbers would have us believe (see J. Infect & Public Health: High Seroprevalence Of Avian Influenza H9 Among Poultry Professionals In Pakistan).
In December of 2019, in EID Journal: Novel Reassortant HPAI A(H5N2) Virus in Broiler Chickens, Egypt, we saw a new proof of concept in the field, after an HPAI H5N8 virus reassorted with an LPAI H9N2 virus, and produced a new HPAI H5N2 virus in Egyptian poultry.
And a year ago the CDC added a second lineage of the H9N2 virus to their IRAT (Influenza Risk Assessment Tool) short list of novel flu viruses with pandemic potential.
H9N2: Avian Influenza A(H9N2) Y280 lineage [A/Anhui-Lujiang/39/2018] Virus
Low pathogenic avian influenza A(H9N2) viruses are enzootic in poultry in many countries in Africa, Asia, the Middle East, and Europe. Since the late 1990s when the first human infections with avian influenza A(H9N2) virus were identified, detection of this virus has been reported infrequently in humans and in swine and other mammals. In 2018, there were 7 reported human infections, most with known exposure to poultry and with the majority involving viruses of the Y280 lineage.
Summary: A risk assessment of avian influenza A(H9N2) Y280 lineage A/Anhui-Lujiang/39/2018 virus was conducted in July 2019. The overall IRAT risk assessment score for this virus falls into the moderate risk category. The summary average risk score for the virus to achieve sustained human-to-human transmission was 6.2. The average risk score for the virus to significantly impact public health if it were to achieve sustained human-to-human transmission was 5.9, also in the moderate range. For a full report click here pdf icon[356 KB, 5 pages].
While perhaps not the biggest pandemic threat we face - very much like the sporadic jumping of swine-variant viruses to humans (see Canada: Manitoba Public Health Reports 2 Unrelated Novel Swine Variant Infections (H1N1v & H1N2v)) - we need to take the species jumping of novel viruses seriously, as even a mild influenza pandemic (on top of COVID) right now would present considerable difficulties.
