There has been much written about the threat of a bird flu pandemic. Much of it is either alarmist or inaccurate. However the truth is not a great deal more digestible.

First I will examine the facts as they stand. The virus in this case has been labelled H5N1 and it is a fairly close relation to the virus H1N1 which caused the “Spanish” flu pandemic in 1918/19. That outbreak followed the Great War (aka World War I) and killed many more than that war itself. Most estimates of the death toll of H1N1 range from 50 million to 100 million!

H5N1 is currently decimating bird stocks around the world and is spreading alarmingly with recent outbreaks in Turkey, Cyprus and now Africa and Italy. In its current form H5N1 is not a great threat to mankind and those who have become infected with the virus have been in close contact with infected birds. But we must not underestimate or ignore the human misery caused by those who have died through infection and the loss to livelihood caused by the destruction of avian farming stocks.

So what is all the fuss about? Simply that viruses tend to evolve and, over time, it is likely that H5N1 will “learn” to infect humans far more easily. Viruses can learn in a variety of ways. One way is through normal evolution and they evolve far quicker than we do – indeed some strains of H5N1 are already showing resistance to Tamiflu – the current antiviral of choice. A quicker route is if the virus should find itself inhabiting the same body as a human flu virus – perhaps in a human being or perhaps in a pig – among other possibilities. When this happens the viruses often swap information.

The consensus of opinion among the great and the good of the scientific community is that it is only a matter of time before H5N1 becomes capable of human-to-human transmission – that it is inevitable!

Once that happens the pandemic begins.

But even then a great deal of uncertainty exists. There are two key statistics when it comes to a virus rather as there are two key statistics when it comes to marketing a web site. In the case of the web site the first key statistic is how many people reading your banner ad/your email promo click through to your web site. The second is how may of those actually buy.

In the case of the virus it is far more morbid. The two key statistics are the infection rate and the mortality rate.

There have been three recognised pandemics in the last 100 years. All three had infection rates of around 25%. The 1918/19 pandemic also had a mortality rate of between 2.5% - 5% which is why it was so deadly. The pandemics of 1957/58 and 1968/69 had mortality rates of around 0.37%.

These statistics are really the source of all the hype and concern because currently H5N1 is killing around 50% of those it infects!

Hence we get claims that 1.5 billion (sic) people will die. The mathematics is simple. We assume an infection rate of 50%, and some say “Spanish” flu infected 50% of people, and we apply the current mortality rate of 50% to the current world population in excess of 6 billion people. Result: one in four dies.

But this over looks a key point. Usually a virus that mutates to become capable of human-to-human transmission becomes much less deadly in the process.

The bottom line – we simply do not know what we might face.

The key question – how much time and money do we spend on a threat which may be a complete damp squib or may decimate human population?