H9N2 Avian Flu Virus Has Pandemic Potential in Humans

GLOBAL - Hongquan Wan of the School of Veterinary Medicine at the University of Maryland has published a paper with a number of co-authors on the pandemic potential of the the H9N2 flu virus in humans. Their work in ferrets led them to suggest that this strain from poultry poses a significant risk to humans as it showed enhanced replication and efficient transmission by direct contact.
calendar icon 13 August 2008
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H9N2 avian influenza A viruses are endemic in poultry of many Eurasian countries and have caused repeated human infections in Asia since 1998.

To evaluate the potential threat of H9N2 viruses to humans, we investigated the replication and transmission efficiency of H9N2 viruses in the ferret model.

Five wild-type (WT) H9N2 viruses, isolated from different avian species from 1988 through 2003, were tested in vivo and found to replicate in ferrets. However these viruses achieved mild peak viral titres in nasal washes when compared to those observed with a human H3N2 virus.

Two of these H9N2 viruses transmitted to direct contact ferrets, however no aerosol transmission was detected in the virus displaying the most efficient direct contact transmission.

A leucine (Leu) residue at amino acid position 226 in the haemagglutinin (HA) receptor-binding site (RBS) - responsible for human virus-like receptor specificity - was found to be important for the transmission of the H9N2 viruses in ferrets.

In addition, an H9N2 avian-human reassortant virus, which contains the surface glycoprotein genes from an H9N2 virus and the six internal genes of a human H3N2 virus, showed enhanced replication and efficient transmission to direct contacts.

Although no aerosol transmission was observed, the virus replicated in multiple respiratory tissues and induced clinical signs similar to those observed with the parental human H3N2 virus.

Our results suggest that the establishment and prevalence of H9N2 viruses in poultry pose a significant threat for humans.


Wan H, Sorrell EM, Song H, Hossain MJ, Ramirez-Nieto G, et al. (2008) Replication and Transmission of H9N2 Influenza Viruses in Ferrets: Evaluation of Pandemic Potential. PLoS ONE 3(8): e2923. doi:10.1371/journal.pone.0002923.

Further Reading

- You can visit the Avian Flu page by clicking here.
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