After a winter of increasingly hysterical press coverage of the risk of a human pandemic, Britain at last experienced the reality of bird flu when, at the end of March 2006, a single dead swan washed up on to the beach at Cellardyke on the east coast of Scotland.

The bird tested positive for the type of the virus designated H5N1, present in many bird populations and which had led to dozens of human fatalities across Asia. It was with almost palpable relief that the U.K.'s Daily Telegraph newspaper was able to declare on its front page "Britain's first bird flu zone," complete with a map showing a "1,000 square mile area at risk."

Like Chekhov's seagull or Ibsen's wild duck, the bird was surely an omen: the next autumn migration season would bring squadrons of sickly foreign birds plummeting from the skies to spread their deadly infection to anything and anyone within range. Several years on, we are still waiting.

Hong Kong beginnings

The story of bird flu as a real hazard to human health began in 1997 in Hong Kong, where eighteen people were infected and six died after coming into close contact with birds at the city's live markets. The outbreak took epidemiologists – the scientists who study the spread of diseases – by surprise as it had been thought that the virus could not jump from birds to humans without the help of an intermediary species such as pigs.

Despite the unpreparedness, further spread of the disease and loss of life was prevented by the rapid cull of all poultry in the city.

In 2003, the H5N1 virus resurfaced - now slightly altered and more dangerous, some commentators likened it to the doomsday bug in Michael Crichton's old thriller, The Andromeda Strain. This time several members of a Chinese family died after having visited relatives who kept chickens. Similar cases began to be reported from Vietnam, Thailand and Indonesia, and the World Health Organization (WHO) announced a pandemic alert.

Through the autumn and winter of 2005, human cases spread westward, recorded with mounting agitation by the European press. Russia, Kazakhstan, Kurdistan and Turkey were hit in turn, as the European Union banned the import of live birds and feathers. All the human casualties were found to have been in close proximity to birds – five Azerbaijani teenagers died after plucking a dead swan.

Face mask fallacy

Shortly before the Cellardyke swan made its final landfall in Scotland, a German cat was found to have contracted the disease; cat-owners were told to keep their pets indoors. One British newspaper was on the point of demanding that the government distribute face masks to the population until it was pointed out that they would actually be useless against the spread of the virus.

So, why such expansive coverage for a disease that had killed a little over a hundred people around the world in three years – about a quarter of the number who die annually in England from resurgent tuberculosis?

The main reason may be what the media habitually refers to as the 'spectre' of the influenza pandemic that struck at the end of the First World War, perhaps infecting as many as a billion people and claiming 60 million lives.

There have been human flu pandemics since – in 1933, 1950, 1957, 1968 and 1977 – but none as virulent as in 1918. Add to this the vague, residual fear that what we sloppily call 'flu' may not be simply the common cold that happens to be heavy enough to allow us to claim a few days off work but something altogether more serious.

Of course, the media thrives on the unrealised threat of mortal disease that could wipe out entire, well, readerships. Bird flu is just the latest of these – after SARS , MRSA and HIV/AIDS. But in the case of H5N1 flu, august public health officials have added fuel to the flames, pronouncing that a killer pandemic is "inevitable."

Epidemiologists merely use the word 'inevitable' to mean that 'there were several serious flu epidemic/pandemics in the 20th century, the virus is able to evolve into new forms against which we have no effective vaccine or natural immunity, and so there is no reason to think that the 21st century will be different'. Or, as the U.K.'s Independent newspaper shrieked, "We face a century of viral pandemics."

"Century of viral pandemics"

Now it is possible – just about – to make out that the twentieth century was a 'century of viral pandemics', although few would define it in those terms despite the devastating advent of HIV. There is no reason to think that earlier centuries fared better, and so none to think that the twenty-first century should not have its share of viral outbreaks too. The question is whether outbreaks will be more frequent or more severe to earn the century this label.

This kind of language is symptomatic of an old tendency to blame ourselves for visitations of pestilence. But here it has a modern dressing of anticapitalism. For author, Mike Davis, SARS and HIV were the "deadly by-product of a largely illegal international wildlife trade, intimately connected with logging and deforestation, which mortally threatens human health as well as regional biodiversity," while avian flu has prospered "in ecological niches recently created by global agrocapitalism."

The Independent's columnist Johann Hari echoes him, saying we will be "plagued by pandemics because of the new virus-friendly ecology we have created across the world." So it's all our own fault, then. It's our affluent lifestyles, our travelling, our migration to the cities that's doing it.

But it is clear that modern life is not mainly to blame. It is quasi-rural backyards with small flocks of chickens where people catch bird flu, not intensive poultry sheds. On the whole we enjoy better food and personal hygiene and experience less risk of picking up an infection from a non-human source than in the past. Even where the risk is still high, the solution through measures such as clean water supply is within our grasp if we are prepared to pay for it.

It is true that an outbreak today is more likely to be global. But sheer geographic spread does not mean that the virus responsible is uncontainable. The pneumonia-like Severe Acute Respiratory Syndrome (SARS) emerged in November 2002 Over eight months, it spread to 26 countries. In all, more than 8,000 people were infected, of whom 774 died.

Spread of SARS

In the most dramatic illustration of the way disease can spread in the global village, a doctor who had attended some of the first victims in China travelled to Hong Kong for a wedding. There he passed the infection to sixteen other guests. Within a day, those people and others whom they infected in turn distributed the virus to half a dozen countries as far afield as Ireland and Canada, ultimately accounting for 355 cases.

The SARS episode now provides an exemplary case study of how a powerful virus spreads – and may be contained. For although SARS did rapidly kill three times as many people as avian flu has done, it was contained relatively efficiently by isolation and quarantine of those infected.

Preparedness in this case did not mean laying in vast stockpiles of a vaccine since SARS was a completely new virus. Nor would some of the usual government reflex gestures such as closing borders have made any difference in time. The key was openness and rapid reporting, rather than the sort of administrative denial that can give a virus time to spread unchecked.

Another lesson applicable to pandemics of all kinds is the importance of accurate diagnosis and decisively taken preventive measures. In general, even very contagious diseases may be controlled by means of appropriate education as much as by high-tech medicine.

If a flu pandemic is indeed 'inevitable', it is equally inevitable that it will start in Asia. It is the high 'viral load' here that tempts epidemiologists to use the word in the first place. All of the modern global flu outbreaks began in China, where many people live crammed into unsanitary conditions, frequently cohabiting with their ducks, chickens and other livestock. The future issue for the rest of the world may be containment; the issue in rural Asia now is domestic hygiene.

Shock tactics

Despite this reality, western governments and media continue to play to the gallery. "If bird flu grips the nation, doctors will need guns," screamed the Sunday Times.

The viral load is nowhere lower than in the United States, yet this is where some of the most hysterical coverage is seen. The New York Times alarmed its readers with news that the vaccine being stockpiled by the U.S. "protects only about half the people who receive it," making it sound for a moment as if survival would be a lottery even for the inoculated. Only later in the story came the admission: "The disease has not reached the Americas."

In Britain, the Sunday Herald newspaper leaked a government study predicting the breakdown of society: "A minimum of 25 per cent of the population will become ill over each six-to-eight-week period ... Mortality is likely to be high – estimated at one per cent of the total population."

Not that there was much to be done about it. At home, nothing yet needed doing. For anywhere else, the precautions were elementary. The U.K. National Health Service advised people travelling to affected regions to avoid close contact with poultry and to wash their hands.

Washing your hands is never a bad thing, of course, but the clueless advice hardly seems commensurate with the claimed scale of the looming disaster and media talk of stockpiling body bags. It recalls that of the hygiene-obsessed economist Edwin Chadwick, who went to his grave restating his belief in "soap and water as a preventative of epidemics" long after the celebrated John Snow had narrowed down the source of the 1848 London cholera outbreak to a particular street pump.

What does it take to catch bird flu?

So far, so terrifying. Perhaps it is more instructive to look at what you have to do to catch this disease rather than what to do to prevent it. What does it take to catch flu from a bird? Scientists discovered in 1974 that the avian flu virus thrives in the guts of wild birds, notably waterfowl.

Unlike familiar forms of human-transmissible flu, which is a respiratory infection passed through the air, avian flu is passed on when healthy birds ingest water containing the excreta of infected birds. For a person to become infected, he or she must have intimate exposure to the excreta or intestines of an infected bird. Taking up voodoo and smearing yourself with the raw entrails of an infected chicken in a sacrificial ritual would thus be a good way to contract bird flu.

Another successful method is to eat (carelessly prepared) raw ducks' blood sausage, which is a Vietnamese delicacy and the cause of some cases in that country. Sharing your accommodation with poultry is hazardous because the birds' excreta or remains are likely to contaminate human food. This explains the majority of human cases of bird flu – no cases have been recorded of people catching the disease from live wild birds or from cooked poultry.

In the U.K., it is statistically true to say that you are more likely to die of rabies than bird flu simply because one man – a professional bat handler – died of bat rabies in 2002.

This comparison may seem facetious, but both avian flu and rabies are – along with HIV, ebola and measles – zoonotic diseases, that is to say they are carried by animals but can pass to humans if the virus mutates in the right way. The comparison illustrates the fact that for both these normally animal-borne viruses a human being has to take extraordinary steps to put themselves at such a disadvantage that infection is possible.

Dangerous mutability

Even then, the avian flu virus must be present in a form that is able to attack human cells. There are 144 possible combinations of the 16 H (haemagglutinin) and 9 N (neuraminidase) chemical groups that dot the surface of a flu virus. H5N1 is one particular combination. The previous flu epidemics of the twentieth century were H1N1, H2N2 and H3N2.

Other combinations arise from time to time – for example, in the Netherlands in 2003 an outbreak of H7N7 led to a cull of 11 million chickens. One person died out of 83 infected by this less deadly strain. But scientists do not know what mutations are needed to produce a dangerous type of the virus. They cannot predict when mutations will appear or what they will be. This makes it impossible to prepare specific vaccines or anti-viral treatments before the new type is present in humans.

It is this mutability that makes flu dangerous. The smallpox virus, for example, has a fixed composition, which has made it relatively easy to eradicate. The H and N groups of the flu virus, on the other hand, may 'drift' into a different form if the amino acids within them are altered.

Darwinian natural selection then ensures that the virus reappears each year in a slightly different version, although this change happens sufficiently slowly that the human immune system is generally able to cope with the new invader. But the virus can also 'shift' rapidly into a new type when a new H or N is introduced, for example from birds. When this happens, there is no ready immunity in the general population.

'Mutation' is also a word made for scare stories. It seems to leap straight from the pages of John Wyndham, where some malevolent biological slime manouevres for world domination using processes clearly outside human understanding or control.

Infective and pathogenic

Mutation is an evolutionary process, but it is not directed. The flu virus is not out to get us, it is simply out to survive, which it already does in the bird population. A sequence of mutations is required for H5N1 to be able to thrive not in a bird's gut but in the quite different conditions of the human respiratory tract. These mutations may or may not occur. And if a human-adapted virus does result, it may or may not turn out to be highly pathogenic.

Paradoxically, a virus that is both highly infective (i.e. it spreads efficiently) and highly pathogenic (i.e. it kills a high proportion of those whom it infects) may not be very dangerous on a global level because it quickly kills too many of its host species to be able to continue spreading. The pandemic threat comes from a virus that is only moderately pathogenic but highly infective.

The 1918 flu was such a virus, infecting more than half the world's population but killing only one in twenty of those it infected. The H5N1 virus circulating today is highly pathogenic (it has killed more than half the humans it has infected) but much harder to catch. If it mutates into a highly infective form, that in turn is likely to make it ultimately less lethal worldwide.

Recorded outbreaks have claimed single victims or small groups of people, almost all of whom can be directly linked to birds. All this means that it is extraordinarily unlikely that, for example, Princess Diana's driver was suffering from bird flu on the night of her fatal car crash (a theory reportedly entertained by the U.K.'s Daily Express). Bird flu remains essentially a disease of birds even though it may have taken the New York Times eight paragraphs in its story about the virus "spreading rapidly through Asia, Europe and Africa" to remind its readers of this basic fact.

Has H5N1 missed its chance?

There are other reasons to worry less about bird flu. The media has repeatedly said that a pandemic is 'overdue' or even 'long overdue'. This claim is not based on any virological dictum, but simply on the historical pattern of outbreaks – one every 10 to 15 years or so from 1918 to 1977 and then a pregnant pause until now. But in fact the longer H5N1 'tries', the less likely it is to succeed in adapting into a human-transmissible type.

Some scientists now believe H5N1 has had its chance. A virus is not like a volcano, where pressure may build up gradually, leading to an eventual eruption. And a continued non-outbreak doesn't make a future outbreak more likely or more deadly.

It seems these truths are at last being acknowledged. In February 2007, H5N1 avian flu rampaged through a Bernard Matthews turkey shed in Suffolk, England, requiring the swift destruction of 160,000 birds. Media talk of an inevitable human pandemic promptly vanished, replaced by a new Dunkirk spirit. When push came to shove, the outbreak was simply something that had to be – and could be – dealt with.

While bird flu has yet to claim a single human victim in Europe or the Americas, and has killed fewer than 300 people worldwide, it is perhaps worth adding that the familiar winter flu that nobody panics about claims at least 30,000 American and 12,000 British lives each year.

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