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No-One Knows If H5N1 Has the Capacity to Mutate into an Infectious Human Disease

Posted on: Saturday, 14 January 2006, 09:00 CST

By IAN JOHNSTON

FUNDAMENTALIST Christians may disagree, but the world is currently on tenterhooks waiting for evolution to deal humanity a bitter blow.

For the rules of Charles Darwin's game of life will determine whether the bird flu virus turns into a global flu pandemic that, according to the gloomiest predictions, could kill as many as 500 million people, causing the collapse of society and the deaths of up to a billion more from starvation, violence and other diseases.

Attempts to forecast what will happen are largely guesswork based on previous pandemics and the truth is that no-one knows if H5N1 even has the capacity to mutate into an infectious human disease. It might happen next week, in ten years time or never at all.

What is reasonably certain is that at some point there will be another flu pandemic with the ability to kill millions of people unless we do something to stop it. When experts say a global outbreak is inevitable, this is what they mean.

It is not a simple thing for a virus which normally infects birds to turn into one that can pass easily between humans.

Human infections to date have been unhappy accidents among people who have got too close to sick birds. But viruses replicate at a colossal rate and the random changes in DNA could eventually throw up a version that by chance is highly infectious in humans.

To do so, it will have to become a significantly different virus from the one that is devastating to poultry.

Professor Ian Jones, a molecular virologist at Reading University, said: "We are seeing evolution in real time here. All the stuff on television about challenges to evolution, if you've got any doubt evolution happens, well here it is. The virus is sweeping through the population in birds."

As the genetic make-up of the disease changes through the generations, it could by chance throw up a strain that can infect humans as well as birds.

The devastating flu pandemic of 1918-19 is thought to have been caused by an "entirely avian" flu, according to a study published last year.

The other way the virus could turn into a human form is if someone who has flu then also contracts the H5N1 strain and the two disease share some genetic information. It is thought the pandemics of 1957 and 1968, which were less severe, were caused in this way.

Professor Jones said the virus would have to mutate in at least two ways. "It has to change the way it gets into cells because the surface of a human cell is different to a bird cell," he said.

"Also, the temperature inside the lungs of a chicken is about 39 to 40 degrees Celsius whereas the upper respiratory tract of a human is about 34 degrees.

"That's quite a bit different. You are asking the virus to do a couple of different things, just the right changes to allow it to replicate - so it can be transmitted by sneezing and coughing - and replicate well. It's a rare event."

While it could actually happen in birds, if there was not a nearby supply of human hosts, the virus with the capacity to kill millions of people worldwide might disappear without a trace. Professor Jones said: "It throws off mutations all the time, but in order to be a successful virus, it must benefit it in the population it is in or it will just die out."

Source: Scotsman, The

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