BF - the risk to humans

The detection of H5N1 virus in a bird in Scotland last week doesn’t change the likelihood of that happening, according to the country’s top doctor. But, with an influenza pandemic long overdue, preparations are underway for the imminent arrival of a devastating outbreak of flu.

Dr Harry Burns, Scotland’s chief medical officer, said the arrival of an H5N1 infected bird in Scotland posed little risk to human health. The chances of a member of the public contracting it from an infected bird were, he said, “infinitesimal”.

“We are warning that if you find a big dead bird, don’t go near it as that is the only way you are going to get it,” he said. “We have no evidence to suggest that a live swan sailing around a public park is a problem.

“Given the numbers of wildfowl that pass through Scotland, it is virtually inevitable that we were going to find something and it wouldn’t surprise me to find more.”

Burns said the situation in Scotland did not increase the risk of a human flu pandemic being triggered.

He said: “If H5N1 is going to mutate into the kind of virus that can be passed from human to human, it is far more likely to do that in the Far East, in an environment where people are living closely with chickens.”

Yet despite the reassurance over the current situation, it is clear that the authorities are taking the threat of a pandemic flu seriously.

The Scottish Executive, along with the rest of the UK, has drawn up contingency plans in the event of a flu pandemic in humans. These include the stockpiling of antiviral drugs as a first response to reduce the extent and severity of the illness.

Scientists are also monitoring the H5N1 virus closely in order to track whether it is mutating into a form that could be passed easily between humans.

Burns said this could give a crucial early warning of a potential flu pandemic situation.

“It hasn’t turned into anything which is showing signs of spreading easily,” he said. “The molecular biologists have tracked down precisely the bits of the virus that they think will have to mutate.

“Therefore every time the virus is isolated they will be looking at it closely to see if it is showing signs of it and we will get early warning of that, especially if it happens in countries which have very intensive surveillance systems.”

But Burns also cautioned that it might be another strain of flu, and not H5N1, that leads to the next flu pandemic in humans.

“Bird flu is a disease of birds that is extremely difficult to pass to humans,” he said. “Quite separately, the World Health Organisation has drawn attention to the fact that we are overdue a [human flu] pandemic.

“Typically every 30 to 40 years going back through several centuries, we think a new strain of influenza has emerged that the population has not had any resistance to and it has caused deaths.

“We are not predicating our decisions on the basis of H5N1, we are preparing for whatever it is.”

One particular concern about the H5N1 virus has been its high mortality rate. Currently around half of the victims worldwide who have caught the disease from birds have died.

Burns said that was one of the reasons that it had not spread easily yet and that a mutated form of the virus could have lower mortality rates.

“If infectious organisms are going to be successful, they have got to be able to be passed on to lots of other people,” he said. “So if this particular virus is going to become a pandemic flu virus it is going to have to become very much less threatening to its host.”

Burns also claimed there is reason to be more optimistic about any influenza pandemic which might be just round the corner.

“We have got fantastic surveillance systems now and we understand viral structure much better,” he said.

“It is important to realise that for the first time in human history we are preparing in advance for a pandemic.

“We have never had the opportunity to do that before.”