Noted virologist and former professor at the Vellore-based Christian Medical College, Dr T Jacob John, speaks to TOI’s Shimona Kanwar about why one should be vigilant about the bird flu, even though it rarely transmits to the human. “Eternal vigilance is the price for the freedom we have from these infections. Every human pandemic starts with an animal or bird virus,” he emphasizes
1 Last year, India was declared free of avian flu. How come we are witnessing another outbreak now?
• This virus cannot be eliminated. It is like a meteor coming in fresh from somewhere. The reservoir of this flu are migratory wild birds. These viruses are in birds’ path wherever they go. If not stamped out where detected, it can continue to spread. An area can become a local reservoir of the virus and affect domestic chicken/ farm also. Nipah virus is another example of such a virus which comes and goes and needs to be stamped out.
2 Do you see a link between Covid-19 and avian flu as both are zoonotic viruses (found in the animals)?
• None whatsoever. Except the timings. It came in 2021. Outbreaks keep on happening here and there in different places globally along the path of the migratory birds. Many birds come during the cold season for migration. The wild birds, who are a source of virus, do not suffer, while new hosts can die in large numbers. Sometimes if there is a new mutant virus, the wild birds themselves can die during flights.
3 Is there any human transmission of this flu?
• The bird flu is mostly a gut infection in the birds and not an upper respiratory tract infection. The species specificity of a virus depends upon whether you have receptors for the virus or not. In most animal viruses, the humans do not have receptors so the virus remains in animals. Birds and animals are natural reservoirs for influenza Type A viruses, and for Type B — humans are natural reservoirs. However, there can be a totally new antigen resulting in pandemic or severe flu in the birds.
This H5N8 is not a new virus and many birds are not seriously affected, but when new colony of farm birds get it, their mortality is very high. The fear is economic loss and not human transmission. Yet, we need to be careful as once in a while, there can be human infections.
4 How to treat such infected birds?
• No antiviral treatment is practical. Only culling is possible. There have been debates that they could be vaccinated. But vaccinated birds may look healthy, get infected and transmit infection to other birds. That is the fear. Also, vaccination of the chicks is not economically viable.