It is only a matter of time. There is no if or but, but only when and what, that a pandemic will hit the globe. We have managed in recent times to stave off avian influenza from scaling up into a pandemic. AIDS is a behaviour and lifestyle infection, which, despite its pandemic spread, can be controlled by a change of behaviour. Not so infections spread from person to person by casual social contact.

Conditions could not be better for the rapid global spread of a new virus like the H1N1 'swine flu' virus. The World Health Organisation (WHO) is estimating that up to two million people could be infected by the virus if the current outbreak turns into a pandemic lasting two years. The organisation's flu chief Keiji Fukuda, with the concurrence of other experts, has pointed out that the historical record of flu pandemics indicates that one-third of the world's population gets infected in such outbreaks. Except that conditions are even better now for more extensive and faster spread of infections than in any previous era.

Epidemics associated with emerging and re-emerging infectious diseases are now occurring in historically unprecedented numbers. Since 2001, the WHO has verified more than 1,100 epidemics of international importance. An epidemic becomes a pandemic when it spreads widely across borders and regions and reaches big chunks of the world.

Cases of human plague have been known from ancient times. One early record of plague was an outbreak among the Philistines (I Samuel, chapters 5 & 6). The biblical record explained this as divine retribution. In the last two millennia, plague has become widespread, affecting a large number of countries on most continents during several pandemics.

The first pandemic that we are certain of is known as Justinian's plague and occurred between 542 AD and 546 AD, causing epidemics in Asia, Africa and Europe. Some 100 million victims are estimated to have succumbed to this disease.

Black Death

The second plague pandemic is the well-known 'Black Death' of the 14th century (1347-1350) which may have killed more than one-third of Europe's population. This pandemic was the beginning of a number of outbreaks of plague, which ravaged Europe and Africa in subsequent centuries. Containment of the Black Death plague took place when the biblical principle of quarantine was rediscovered and applied.

The third pandemic began in Canton and Hong Kong in 1894 and spread rapidly throughout the world by rats aboard the swifter steamships that had replaced slow-moving sailing vessels in merchant fleets. Within 10 years (1894-1903), that outbreak of plague is believed to have entered 77 ports on five continents. In India alone, there were over six million deaths from 1898 to 1908.

The Spanish Flu of 1918 first appeared on a military base in Kansas. Men who carried the disease, believed now to have been transmitted from birds to humans, left Fort Riley to fight in World War I. They spread the flu at each stop, which led to a nearly worldwide pandemic. The Spanish Flu claimed more lives than the fighting during World War I.

There are a number of reasons why the world faces huge risks of a pandemic despite the massive advances in science and medicine, and, indeed, because of some of those very advances.

In the first instance, super-bugs are emerging which are resistant to antibiotic treatment. The massive, wide-scale use of antibiotics, some would say abuse, has pushed genetic selection for resistant strains. Every time we ask our doctor for quick-fix antibiotic treatment for a minor infection that will soon go away through the body's own immune response, we are contributing to the emergence of resistant germs. Multidrug-resistant tuberculosis today, for example, can only be treated by a cocktail of newer antibiotics, and that with difficulty. Creating newer and better antibiotics and vaccines one step ahead of super-bugs simply cannot continue forever.

Then, the artificial chemical environment that humans have created from tens of thousands of synthetic compounds, some of them mimicking biological compounds and affecting biological processes, is driving an unprecedented rate of mutation among micro-organisms whose life cycles are measured in only minutes. Increased inflow of ultra-violet rays and other short-wave radiation from space through a depleted protective ozone layer may also be accelerating the rate of mutation.

Immunologically vulnerable

Flu virologist at Cambridge University, Chris Smith, says of H1N1, "You are talking about a virus that no one in the population has seen before and, therefore, everyone is immunologically vulner-able. Therefore, it is highly likely that once it starts to spread, people will catch it." Something new at some point in time will snowball into a pandemic.

The WHO estimates more than 70 per cent of new and emerging diseases originate in animals. Ironically, humans have never been less in direct contact with wild animals, proportionally, than they are now. But the 'scientific' rearing of domestic animals in close confinement on recycled feedstock and in close contact with humans has given us mad cow disease, bird flu, and now, swine flu.

And now we have unprecedented means for spreading infectious diseases rapidly. Within days of swine flu cases emerging at the epicentre in Mexico, cases emerged in New Zealand and Hong Kong, on the other side of the planet, not to mention neighbouring United States. Now there are cases in over 30 countries - and counting.

Air travel

Thanks to rapid global air travel, it is no longer "Around the World in Eighty Days" by steamer, as in that famous 1873 Jules Verne novel, but around the world in 24 hours by jet. And wearing nose masks against H1N1 would be funny if the whole thing were not so serious. In many infectious diseases, infectiveness precedes symptoms. And, in any case, infection can be by circuitous routes. Quite a bit of the public-health response (like 'sterilising' schools in Mexico) is only providing soothing public relations.

Another factor literally inviting a pandemic is the massive urbanisation of populations. In the ancient and mediaeval plagues, no city exceeded at most a couple of hundred thousand people. Now, cities, connected by aircraft, are packing double-digit millions of people, which makes spread of infection a sneeze.

I don't wish to unduly frighten anyone with pandemics. And, led by the WHO, humans have to put up the best fight we can. But conditions are exceptionally favourable for a big one, perhaps bigger than anything previously seen.

Martin Henry is a communications consultant who may be reached at medhen@gmail.com or columns@gleanerjm.com.