Doctors warned
to watch out for
deadly new flu

In the space of one month, the avian virus strain known as H7N9 has spread through all 31 Chinese provinces and claimed 125 victims, killing a fifth of those infected.

Scientists say it is mutating rapidly and already has acquired two of five genetic changes believed to be necessary for human-to-human transmission.

Currently the virus has made its home in chickens, and has only affected people who have had close contact with the birds, often at live markets.

If it were to become fully adapted to human hosts it could result in a serious worldwide pandemic claiming millions of lives.

Experts speaking in London yesterday said there was no room for complacency over H7N9, and warned against the folly of assuming it was a far-away foreign problem. Letters sent to GPs are advising them how to identify cases and what action to take if one is suspected.

An ever present possibility is someone importing the virus into the UK from China. If a case were confirmed, they would have to be isolated and treated quickly. Details of his or her history and contacts with other people would also have to be obtained.

The experts pointed out the virus was sensitive to antiviral drugs such as Tamiflu, stocks of which remained in the UK after the swine flu pandemic of 2009-10. But currently there is no readily available vaccine.

Research is ongoing into how the virus is behaving and what makes it so virulent – it has infected people of all age groups, suggesting humans have no natural immunity to it.

So far 20 per cent of victims have died, 20 per cent are recovering and the rest remain ill. In fatal cases, the virus has triggered sepsis, leading to multiple organ failure.

Professor Peter Openshaw, director of the Centre for Respiratory Infection at Imperial College London, said: “This is a very, very serious disease in those who have been infected. So if this were to become more widespread it would be an extraordinarily devastating outbreak.

“It’s very unusual to see more than 100 new cases in a very short time period. I think it’s definitely something we need to be concerned about.”

Scientists have learned lessons from the H5N1 bird flu strain, which also emerged in China and, with a 60 per cent mortality rate, is more deadly than the new strain. Since 2003 it has led to 628 confirmed cases in 15 countries and 374 deaths.

Although there is no reason to think that H7N9 will acquire the ability for human-to-human transmission any time soon, it already displays some degree of human adaptation.

In H5N1, five key genetic changes were identified that scientists believe made the virus a potential pandemic threat.

Laboratory studies have revealed two of these mutations in H7N9. One of them is integral to the “H7” part of its structure and enables the virus to latch onto certain receptor molecules in the human respiratory tract. The other has only been acquired after human infection and helps the virus to replicate inside cells.

How easy or difficult it might be for the other three changes to occur, and to what extent H7N9 needs the same mutations as H5N1 to pass between humans, is unknown.

Dr John Watson, head of respiratory diseases at Public Health England, said it was important not to assume there was no threat to the UK. “It might be tempting to feel, fine, let’s just sit back and wait,” he said.

“We feel it’s important nevertheless to be taking this very seriously, because of the illness that it’s caused, because of the novelty, and because of the possibilities there are about what it does next.”