#18,490
While the next novel pandemic virus could arise anywhere in the world (see yesterday's blog Preprint: Rapid Surge of Reassortant A(H1N1) Influenza Viruses in Danish Swine and their Zoonotic Potential), history suggests there is a good chance it will come out of China.
During the 20th century, 2 of the 3 major influenza pandemics (1957 Asian Flu, 1968 Hong Kong Flu) originated from Asia, and our current HPAI H5 threat originated in Guangdong Province, China nearly 30 years ago.
Additionally, during the last decade China saw the emergence of a multi-year avian H7N9 epidemic (2013-2018), and in 2014 they reported the first of (now > 90) H5N6 spillover events. And five years ago this month, we saw the first reports of what would be known as COVID emerge from Wuhan, China.
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).
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.
Today we've a new report on H10N3, published in Veterinary Microbiology, which finds 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 report on a serology study of poultry workers, which found a small but significant (1.5%) positivity rate.
Due to its length, I've only posted some excerpts below. Follow the link to read the report in its entirety. I'll have a postscript after the break.
The novel H10N3 avian influenza virus acquired airborne transmission among chickens: an increasing threat to public health
Authors: Xiaoquan Wang, Huiyan Yu, Yahao Ma, Pinghu Zhang, Xiyue Wang, Jianyu Liang, Xiuling Zhang, SHOW ALL (20 AUTHORS), Xiufan Liu https://orcid.org/0000-0002-9924-6646 xfliu@yzu.edu.cn
https://doi.org/10.1128/mbio.02363-24
ABSTRACT
Following two human infections with the H10N3 avian influenza virus (AIV) in 2021 and 2022, a third case was discovered in Yunnan, China, in 2024, raising concerns about the potential for future pandemics. Recent studies have indicated that novel H10N3 viruses are highly pathogenic in mice and can be transmitted between guinea pigs via respiratory droplets without prior adaptation. However, the biological characteristics of novel H10N3 in poultry have not been fully elucidated. Our findings revealed that H10 subtype AIVs are predominantly prevalent in waterfowl.
Notably, H10N8 and H10N3 viruses that have infected humans were primarily isolated from chickens. For the first time, double basic hemagglutinin cleavage sites (motif PEIKQGR↓GL) were identified in novel H10N3 AIVs, which exhibit enhanced replication in chickens, and can be transmitted between chickens through direct contact and respiratory droplets. Animal experimental studies demonstrated that ducks are also susceptible to H10N3 viruses and that the virus is transmissible through direct contact, suggesting a greater risk of transmission and recombination. Serological studies conducted among poultry workers suggest that while the human population was largely naïve to H10N3 infection, sporadic and undetected human infections did occur, indicating a potential increasing trend. These data further emphasize the growing threat to public health posed by zoonotic H10N3 subtype AIVs.
IMPORTANCE
Exposure to poultry in live poultry markets (LPMs) is strongly associated with human infection with avian influenza viruses (AIVs), with chickens being the most common species found in these markets in China. The prevalence of AIVs in chickens, therefore, increases the risk of human infection. Notably, the main host of the novel H10N3 virus has shifted from waterfowl to chickens, and the virus can be transmitted between chickens via respiratory droplets, posing a potential risk of a pandemic within poultry populations. The novel H10N3 virus also remains sensitive to ducks and can be transmitted through direct contact, which means a greater risk of transmission and recombination. Significantly, the human population remains largely naïve to H10N3 infection, but sporadic seropositivity among poultry workers indicates previous exposure to H10 subtype AIVs. Therefore, a comprehensive surveillance of the novel H10N3 viruses in poultry is imperative. Effective control of the virus within poultry populations could significantly reduce the risk of emerging human infections.
(SNIP)
Serological results from poultry workers
From 2023 to 2024, we collected a total of 2,769 serum samples from poultry workers. The human-derived H10N3 virus strain Hu/JS428 was used as the antigen for this study. As shown in Table 1, we collected 637 and 943 serum samples from poultry workers in 2021 and 2022, respectively, and there is one positive sample in each of the two years. It is noteworthy that among the 790 serum samples collected in 2023, four were found to be positive, while among the 399 serum samples collected in 2024, six were identified as positive, resulting in a positivity rate of 1.5%. These findings suggest that the human population was largely naïve to H10N3 infection during the study period. However, sporadic and undetected human infections did occur, indicating a potential increasing trend.
(SNIP)
In summary, the H10N3 viruses’ main host shifted from waterfowl to terrestrial poultry, and acquired the ability of airborne transmission during nature adaptation in chickens. Additionally, it also maintained sensitivity to waterfowl. The human population was also naïve to H10N3 infection, but sporadic seropositivity among poultry workers does exist. Thus, a comprehensive surveillance of the novel H10N3 viruses in chickens and wild waterfowl is imperative, and control of the virus endemic in poultry could decrease the risk of emerging human infections.
Although we get very little in the way of real-time reporting on avian flu out of China, their scientists continue to publish excellent (albeit, often belated) reports in the scientific journals.
The overarching message from these reports is that avian influenza viruses continue to expand - both in range and variety - across China, and that some of these viruses pose legitimate public health risks.
While most will end up as evolutionary failures, we need to pay attention, because it only take one over-achiever to send us down the pandemic path again.
