A subtype of avian influenza found in Chinese poultry farms is undergoing mutations which may increase the risk of widespread human transmission.
This is the warning of a team of scientists from China and the UK, who are calling for “concerted research” to monitor the evolution of the viruses and the threat they may pose.
In humans, infection with the H3N8 avian influenza virus has been known to cause acute respiratory distress syndrome — and can even be fatal.
However, exactly how it might be transmitted from animals to humans has been poorly understood.
In their study, the researchers analyzed a sample of H3N8 taken from a human patient, using laboratory ferrets and mice as models for human infection.
They found that the strain has undergone several adaptive changes that allow it to cause severe animal infections — and have facilitated airborne transmission between animals.
The analysis was undertaken by veterinary molecular medicine expert Professor Kin-Chow Chang of the University of Nottingham and his colleagues.
Prof. Chang said: “We demonstrate that an avian H3N8 virus isolated from a patient with severe pneumonia replicated effectively in human bronchial and lung epithelial cells.”
(Epithelial cells are those that line the airways and make the mucus which lubricates and protect the lungs.)
The virus, Prof. Chang continued, “was extremely harmful in its effects in laboratory mammalian hosts and could be passed on through respiratory droplets”.
Paper co-author and veterinary medicine researcher Professor Jinhua Liu of the China Agricultural University in Beijing added: “Importantly, we discovered that the virus had acquired human receptor binding preference and amino acid substitution PB2-E627K, which are necessary for airborne transmission.
“Human populations, even when vaccinated against human H3N2 virus, appear immunologically naive to emerging mammalian-adapted H3N8 avian influenza viruses and could be vulnerable to infection at epidemic or pandemic proportions.
“Acid resistance of influenza virus is also an important barrier for avian influenza virus to overcome to acquire the adaptability and transmissibility in new mammals of humans.
“The current novel H3N8 virus has not acquired the acid resistance yet. So, we should pay attention to the change in acid resistance of the novel H3N8 virus.”
The full findings of the study were published in the journal Cell.
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