Aside from the economic implications of culling millions of birds due to avian flu outbreaks, the risk of increasing human infections has been a rising concern.
Now, a study from researchers in China and England has discovered that a subtype of avian flu virus, endemic in poultry farms in China, is undergoing mutational changes, which could increase the risk of the disease being passed on to humans.
Researchers also say that the findings raise concerns of a potential epidemic or pandemic in the making and that concerted research is necessary to monitor such viruses in poultry and humans closely.
The results, which have been published in Cell, report on the characterization of a human isolate — from a human patient — of the H3N8 avian influenza virus.
Using laboratory mice and ferrets as models for human infection, the study found that the virus has undergone several adaptive changes to cause severe animal infections, making it transmissible by the airborne route between animals.
In humans, the avian H3N8 virus infection has been found to cause acute respiratory distress syndrome and can even be fatal. The virus is widespread in chicken flocks; however, previously, the features of how it might be transmitted from animals to humans is poorly understood.
“We demonstrate that an avian H3N8 virus isolated from a patient with severe pneumonia replicated efficiently in human bronchial and lung epithelial cells was extremely harmful in its effects in laboratory mammalian hosts and could be passed on through respiratory droplets,” says Professor Kin-Chow Chang, at the University of Nottingham in England.
The scientists discovered that the virus had acquired human receptor binding preference and amino acid substitution PB2-E627K, which are necessary for airborne transmission.
Even when vaccinated against the human H3N2 virus, human populations appear immunologically naïve to emerging mammalian-adapted H3N8 AIVs and could be vulnerable to infection at an epidemic or pandemic proportion.
“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 or humans. The current novel H3N8 virus has not acquired the acid resistance yet. So, we should pay attention to the change on acid resistance of the novel H3N8 virus.”
