Scientist Warn That Outbreak Of Novel Zoonotic Avian Influenza Virus A(H3N8) In Poultry In China Could Lead To A Serious Human Pandemic!
Researchers from the University of Hong Kong are warning that a current outbreak of a new zoonotic avian influenza virus among poultry and other birds in China and Hong Kong could lead to a serious human pandemic if surveillance and measures are not put into place soon.
Zoonotic and pandemic influenza continue to pose threats to global public health.
Typically, pandemics arise when novel influenza A viruses, derived in whole or in part from animal or avian influenza viruses, adapt to transmit efficiently in a human population that has little population immunity to contain its onward transmission. Viruses of previous pandemic concern, such as influenza A(H7N9), arose from influenza A(H9N2) viruses established in domestic poultry acquiring a hemagglutinin and neuraminidase from influenza A viruses of aquatic waterfowl.
The study team reported the identification of a novel influenza A(H3N8) virus in chicken that has emerged in a similar manner and that has been recently reported to cause zoonotic disease.
Though the new avian influenza viruses are H3 subtype, these viruses are antigenically distant from contemporary human influenza A(H3N2) viruses, and there is little cross-reactive immunity in the human population.
Hence should these viruses crossover to humans, there is likely to be more serious outcomes.
The study team says that it is essential to heighten surveillance for these avian A(H3N8) viruses in poultry and in humans.
The study findings were published in the peer reviewed journal of the U.S. CDC called Emerging Infectious Diseases.
Corresponding author Professor Dr Malik Peiris, a virologist from the University of Hong Kong told Thailand Medical News
, “It should be noted that the influenza A virus has diverse avian and animal origins with several viral subtypes; those in aquatic birds differ in neuraminidase (N1-N9) and hemagglutinin (H1 – H16).”
The subtypes H6 and H9 of the influenza A virus infect game birds like pheasants, quails, and domestic chickens. H9N2 viruses containing acquired neuraminidase (NA) and hemagglutinin (HA) genes generate H5N1, H5N6, H10N8, and H7N9 viruses that may infect poultry and thereby threaten another zoonotic outbreak and onset of a pandemic.
The study team discovered the novel influenza A virus (H3N8) in live poultry in Hong Kong and they were genetically similar to the zoonotic H3N8 viruses reported in mainland China with its origin akin to H5N1, H5N6, H10N8, and H7N9 viruses.
The study team also conducted a risk assessment approach to estimate the effects of human age stratified immunity in a population.
The research entailed virologic surveillance between December 2021 and March 2022.
The influenza A(H3N8) virus was identified in samples collected from four farms (A-D) in the study duration. All four farms were serologically positive for past H3N8 infections.
All the caretakers were advised to disinfect their farms thoroughly and strengthen their biosecurity
measures. Follow-up testing was conducted in May 2022 and again at the end of June 2022; all four farms tested negative for the influenza A(H3N8) virus.
In January 2022 till June 2022, many swab samples of drinking water from poultry cages, defeathering machines, fecal droppings, and chopping boards were sampled from stalls and markets.
The study team found one swab specimen from a defeathering machine and another from a chopping board from two different live poultry markets were H3N8 positive. DNA barcoding determined that the virus detected in the swab specimens originated from domestic chickens.
Subsequent full-genome phylogenetic analysis of the isolated influenza A (H3N8) viruses revealed a close relationship between H3N8 viruses isolated from farms and poultry markets and an H3N8 viral strain implicated in the zoonotic outbreak in mainland China.
It was found that the polymerase acidic, nonstructural protein, NA, polymerase basic 1 and 2, and M gene segments were identical to the G57 sub-lineage of the H9N2 virus found in mainland China.
The sequences of the HA gene were derived from the Eurasian avian H3 lineage, which is found in wild birds and ducks. NA gene sequence of H3N8 in poultry A was from the North American lineage.
However, on the other hand, the N8 NA sequence detected by DNA barcoding of a virus from a fecal specimen in Hong Kong in 2018 was derived from Northern pintail duck or Anas acuta.
Also, two H3N8 viruses from fecal dropping samples from Hong Kong were related to the Northern shoveler duck or Anus clypeata; these strains were unrelated to chicken H3N8 in all gene segments.
The study team found a similarity between the N8 gene segment sequence and the H3N8 virus from other aquatic birds in mainland China. Except for the N8 NA gene segment, no other gene segments detected in poultry Influenza A(H3N8) virus were from the wild bird H3N8 virus from Hong Kong.
Subsequent referencing was carried out of HI titers with the World Health Organization (WHO) antiserum to A/Switzerland/8060/2017 against A/chicken/MKT-AB13cp/2020 H3N8 virus and on comparing with the A/Switzerland/8060/2017 homologous virus.
Importantly, limited antigenic cross-reactivity was noted among the novel avian influenza A(H3N8) virus and the seasonal human H3N2 viruses.
It was found that the overall seroprevalence was insignificant in human serum samples stratified by age. In contrast, high seroprevalence in the same serum samples was observed in a recent seasonal influenza A (H3N8) virus in humans.
The study team warned that herd immunity is an important parameter when assessing any pandemic threat of zoonotic origin.
The study team also warned that this new influenza (AH3N8) virus might pose a serious zoonotic and pandemic threat. Hence, they recommended that poultry surveillance for this virus be enhanced, a comprehensive risk assessment be conducted, and pandemic seed vaccine strains be prepared if necessary.
It should be noted that the first ever human case of H3N8 avian flu was already confirmed in China on Tuesday, 26 April 2022 and since then, according to local physicians and researchers, a number of small sporadic outbreaks among locals have already been found but are being concealed by the Chinese authorities. In almost all cases, disease severity was observed and all required hospitalization.
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