A new plague: The epidemic is coming

We're in for another epidemic. You probably don't want to hear that; we've had enough with bluetongue, foot-and-mouth and bird flu in animals. We're only just beginning to calm down as the bird flu threat to humans apparently recedes, but mad cow disease seems only yesterday and our hospitals are cesspits of MRSA and C.difficile. Haven't we had enough? And how can I be so sure that we're due for more?

The first answer is: history. Infectious diseases have been with us since the dawn of time. In the last century they accounted for more deaths than all the wars combined; indeed during most conflicts until the American Civil War of 1861-5 deaths from infection off the battlefield exceeded those from wounds. But surely the invention of penicillin, proper sewerage and vaccination should have got rid of them for good?

I'm afraid not. My research is not, generally, concerned with the obvious culprit – resistance. The number of people dying of resistant bacteria, although increasing, is small. Nor am I banging a drum about the lack of clean drinking water that is killing millions. I am concerned with the epidemics that are likely to trouble us in the West: how they might get to us; what they might do; and how (if at all) we can protect ourselves.

Allergy

Let's begin with a proven and developing epidemic that is already with us: the epidemic of auto-immune disease (where the body attacks itself), which includes asthma and allergy. The number of admissions for life-threatening allergic reactions has increased by 600 per cent since 1990. Many statistics point to the same thing, that auto-immune diseases are increasingly common. They are the third most frequent diagnosis in the US after heart disease and cancer, with between 14 and 22 million people affected.

Why are they so common? Many readers will be familiar with the so-called "hygiene hypothesis", which suggests that allergy arises from living in a too-clean environment. Our immunity is at a loose end and will go into overdrive at the slightest trigger. The obvious conclusion here is that we won the battle against infectious epidemics, but at the price of allergies.

Cancer

However, that conclusion is incomplete, and for reasons connected to the second epidemic currently gripping us: cancers. Cancer will kill one third of us. A very strange infection is at the root of both auto-immune disease and cancer.

It's long been known that many infections can cause cancer – Gardasil, the wart virus vaccine that protects against cervical cancer, is currently in the headlines as the Government has approved its use for girls aged between 12 and 13 – but what is more interesting is another kind of virus, identical in structure to HIV, that may cause both cancer and auto-immunity. These are the human endogenous retroviruses, or Hervs.

A whopping 8 per cent of human genes are made of these viruses. Unlike HIV, they are inherited rather than acquired during life. There is absolutely no doubt that Hervs can cause cancer. It is becoming increasingly clear that they cause other diseases, too, including auto-immune ones.

This is our newest epidemic: a growing list of common diseases that are caused by Hervs. It already includes diabetes, rheumatoid arthritis, lupus, psoriasis and maybe even schizophrenia. Sadly, because they're hereditary, you can't cure them, but that isn't to say that they won't one day be treatable. Watch this space.

HIV

With 25 million people already dead, declaring that we are at risk of an epidemic of HIV barely seems to be news. However, there is a real risk of a "second wave" of disease in the West. To understand why, you have to look back a little to the history of HIV and its treatments.

In 1996, the penny dropped that suppression of the Aids virus required combined treatment with several drugs. With single drugs, resistance emerged rapidly. Highly active antiretroviral therapy (Haart) seemed almost miraculous: moribund patients recovered and wards cleared (and even had to be closed). At the heart of this was the meticulous management of the disease by skilled physicians backed up by proper laboratory facilities.

However, if HIV is exposed to drugs in a disorganised manner it learns to evade them, and permanently, through resistant mutants. It used to be believed that such mutants would be less "fit" and, thus, incapable of transmission. We now know this to be untrue, to the extent that we test all newly diagnosed cases for resistance mutations before starting treatment.

Let's look at a comparable disease, tuberculosis. Like HIV, this disease has to be treated rigorously with a combination of drugs to prevent resistance emerging. But the toothpaste is already out of this particular tube. In one study in Nigeria, only 50 per cent of patients received the correct drugs; the rest were fake, incorrectly prescribed or sold on by previous patients. Through defective treatment like this, TB resistance has emerged worldwide and it is coming our way. In Lithuania, for instance, a quarter of all newly diagnosed TB is resistant to at least two drugs. TB drug resistance is increasing in the UK.

There has been much pressure to supply cheap, "generic" HIV drugs for the developing world and this is where it all may go horribly wrong. Should the tuberculosis experience be repeated with HIV – and there is no reason to suppose that it won't – we risk a second wave of HIV which is resistant to all our hard-won drugs.

That is not to say that we could not still supply the drugs cheaply, it is just that we have to be sure that the job is done properly. We are all in this together for practical as much as moral reasons. Disaster is already happening with tuberculosis. Don't let us die of ignorance.

Polio

This is just as true with my next possible epidemic, polio. This disease usually attacks in childhood and causes irreversible nerve damage up to and including paralysis and death, if the respiratory muscles are involved. Before widespread vaccination, up to 6,000 people a year used to die from it in the US alone. It is now very rare in the West and was scheduled for eradication by the World Health Organisation in 2005. Then something bad happened.

False rumours began to circulate in the developing world that the polio vaccine was deliberately contaminated with HIV. Vaccinations began to fall off. The first country to be affected was Nigeria, but subsequently 16 other nations in the region suffered polio outbreaks from direct spread. These are still continuing.

You may think this a distant, irrelevant concern for us, but there are two very important consequences. The first is that as long as polio exists in the world, future generations everywhere remain at risk. The second is that this represents a disturbing trend for faith in Western science. There is no doubt that vaccination has been the single greatest contributor to the suppression of infectious diseases. The panic over the MMR vaccination is part of this same troubling trend, and in this respect there is no difference between the anti-Western Muslim preachers who opposed the polio vaccine and the semi-informed parents who rejected MMR. Their actions have consequences, and not just for their own children.

In 2006, a child died of measles in the UK, the first person to do so for 14 years. Who knows what will happen in the countries that have fallen under an anti-Western caliphate? My message is clear: we must keep taking the medicine.

Disease X

My final future epidemic is Disease X. This is the unknown one lurking in a bat cave or incubating in some wild animal. This is not a fanciful suggestion. Remember Sars? Although it belonged to a recognised group of viruses, it was new as a disease in humans – and as such had a high mortality. The Nipah and Hendra illnesses may be less familiar, but these related and previously unknown viruses killed people and animals in Malaysia and Australia in 1998-9.

All of these "new" diseases have something in common: they arose from our contact with animals. Sars arose from Chinese delicacies like dragon-tiger-phoenix soup, where the tiger is the Sars-carrying civet cat. Nipah and Hendra came from fruit bats via other species, including pigs. The number one killer in the developing world – HIV – came from chimpanzees. Almost certainly there are other diseases that will emerge as we continue to encroach into new habitats. Can we do anything about it? Your guess is as good as mine.

You may think it strange that I have not included the most obvious and fashionable reason for new epidemics – climate change. There is no doubt that some diseases such as malaria are ascending to higher altitudes in mountainous areas as the world warms. But malaria in Middlesex? Until recently I would have said I don't think so. But now, with bluetongue in Suffolk? Hmmm...

Why are we so at risk of infectious epidemics? It is because we are made of epidemics ourselves, and in some very strange ways. A large part of us (45 per cent of our genes) is made of viruses and bacteria. In the end we may even be the terminal epidemic on the planet, poisoning ourselves with our own exhausts. Much like a petri dish of bacteria, in fact...

'Epidemic', by Robert Baker, is published by Vision, priced £10.99. To order a copy for £9.89, including postage and packaging, call Independent Books Direct on 08700 798897, or visit www.independentbooksdirect.co.uk