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Bird Flu Arrives
'In view of the high mortality of human influenza associated with this strain, the prospect of a worldwide pandemic is frightening.'
Editorial, The Lancet, January 2004
On 22 October 2005, a parrot was found dead in quarantine premises in the UK. The death of a parrot would not normally be big news, but this parrot's demise made all the front pages in the UK and topped the TV news instantly. The parrot was, of course, the UK's first confirmed victim of avian influenza type H5N1, or 'bird flu' as it's more popularly known.
Suddenly, bird flu caught everyone's attention. It was no longer something remote, happening to chickens in Asia. It was in the West, now. People wanted to know just what it was, how you could catch it, how you could treat it if you did catch it, and much more besides. Questions were asked of ministers. Newspapers demanded action. Rumour spread that eating chicken was dangerous, and some supermarkets reported a dramatic plunge in sales of chicken. Wealthy City firms were said to be stocking up on the drug Tamiflu to treat their staff should bird flu make its way into London's Square Mile (a pattern repeated in the USA).
If for a while it seemed to some Americans that this was just a local crisis over the Atlantic, then a week later their complacency was shattered. On 1 November 2005, President Bush announced a plan to spend over $7 billion to prepare the country against the flu threat - an astronomical sum for a disease that doesn't yet exist. It transpires that US health officials have already been long aware of the threat, and the plan has been four years in preparation. This summer George Bush's vacation reading was apparently John M. Barry's bestselling book, The Great Influenza, about the terrible outbreak of flu that swept the world in 1918. 'There is no question that the tipping point has finally arrived', says Tommy Thompson, Mike Leavitt's predecessor as Health Secretary. Bird flu is now big news.
For most of us - except for the elderly, the very young and those with chest problems - flu is just one of those annoying things about winter, a bug that lays you low for a few days and makes you feel quite poorly but is ultimately just a nuisance. Now, however, people are finally beginning to take notice of what some experts have been saying for years. Influenza is not just a mild bug; it is actually one of the world's major killer diseases.
Working hand in hand with respiratory diseases such as pneumonia and tuberculosis, certain strains of flu claim a steady toll of hundreds of thousands of lives each year. This is disturbing enough, but flu is a remarkable virus that is constantly changing and evolving. Every now and then, particular killer strains of flu emerge that suddenly sweep out across the world in great worldwide epidemics or 'pandemics'. The most notorious, and deadly, was the Great Influenza in the aftermath of the First World War, which recent estimates think might have killed up to 100 million people. But there have been several more pandemics since, at regular intervals less severe, but still claiming many lives. These pandemics occur when a particular strain of flu jumps the species barrier from birds or pigs to humans. Human bodies are then faced with a new germ to which they have no natural immunity, and which can prove far more deadly than run-of-the-mill 'winter' flu. Barely 1 or 2 percent of people who catch these killer flus actually die, but 1 or 2 percent of the world's population is a lot of people.
The next pandemic?
Most experts believe that it's not a question of 'if' we have another pandemic like the Great Influenza, but 'when'. Many say that the next great pandemic is now actually overdue. At the moment, the H5N1 virus, the strain of flu that killed the parrot, is mainly confined to birds. So far it's known to have killed fewer than a hundred people, and most of these had direct and close contact with chickens. The fear is that the virus may become able to spread between humans. If so, then it could set alight the next great pandemic.
World Health Organization spokesmen are not given to wild overstatement, but in November 2004 the WHO's Shigeru Omi said the death-toll in such a pandemic may be 'in the worst case, 100 million'. One Russian virologist, Dmitri Lvov, says that more than a billion may die. The plain fact is that no one really has a clue just how bad it could be. As the WHO's head, Klaus Stöhr, said in a remarkably honest statement to the UK Times: 'No one knows how many are likely to die in the next influenza pandemic ... The numbers are all over the place.' Yet although we don't know just how bad, the consensus is that the next great flu pandemic will be bad.
At the moment, though, no one knows if the H5N1 bird flu is the germ of the next pandemic, or if it will remain confined to birds alone. Health spokesmen, anxious to avoid panic, have stressed that it's basically a disease of birds, and that we therefore have nothing to fear. As they point out, most of the few people who have so far died are poor farmers who live in very close contact with their chickens. However, in August 2004, a young Thai woman died from bird flu caught from her daughter, who in turn caught it from chickens and this woman passed it on to her sister, who was treated with Tamiflu and recovered. So there is absolutely no guarantee that bird flu will never pass between humans.CHAPTER 2
'... man starts in as a child and lives on diseases to the end as a regular diet.'
To the hunter-gatherers of the early days of mankind, infectious diseases were probably virtually unknown. These people didn't live close enough together for germs to spread, or stay long enough near water sources to pollute them. Nor did they have the tame animals that today harbour all kinds of germs. But as people colonized the world, so they too were colonized by germs, from parasitic worms to bacteria to viruses. The discovery of farming some 10,000 years ago saved mankind from starvation and provided food for a massive population explosion. But by allowing people and animals to live close together it promoted the conditions which allowed infectious disease to thrive for the first time.
Farm animals shared their germs with humans directly. Cattle gave us tuberculosis and smallpox. Dogs gave us measles. Horses gave us that annoying winter scourge, the common cold. And maybe chickens or pigs gave us flu. As farming became more intensive, manure-polluted water allowed diseases such as polio, cholera, typhoid and hepatitis to thrive, while irrigation water provided ideal conditions for parasites such as those causing bilharzia and schistosomiasis - not to mention malaria.
Humans were by no means defenceless against this rising tide of infectious disease. As each infection struck, so survivors acquired antibody protection, and natural immunity to an increasing number of diseases was passed on from parents to children in the womb or through breast milk.
Waves of disease
But throughout history, waves of epidemics have spread across the globe, becoming increasingly deadly as populations grew and people moved around more and more. In AD 165-180, the Antonine plague killed a quarter of the Roman Empire's population. About 1300, the Black Death (bubonic plague spread by rat fleas) began its sweep across from the Middle East through Europe and North Africa, culminating in the dreadful years of 1346-50, when 20 million people died and whole villages were wiped out.
Virgin populations, with no natural immunity, proved particularly vulnerable to introduced diseases. When the Spanish conquistador Cortés conquered the Aztecs in 1521, most of the Aztecs fell victim not to Cortés's little band of marauders but to the deadly smallpox they brought with them. The first epidemic to hit the Americas from Europe, though, was probably swine or Spanish flu, brought by the pigs on Columbus's ships. Over 400 years later, another outbreak of swine flu proved to be the worst epidemic ever. In 1918-19, swine flu swept around a world still shell-shocked by the Great War, and killed 60-100 million people - far more than the war itself.
Just as the farming revolution 10,000 years ago brought its share of diseases, so too did the Industrial Revolution 200 years ago. The crowded conditions in the new towns of the 19th century allowed wave after wave of epidemics of cholera to take a deadly toll among the poor who lived so close together in filthy places.
As later chapters show, increasing urbanisation in the Third World today is repeating this pattern, proving an all-too-rich breeding ground for diseases like flu.
New diseases are continuing to appear, including HIV, Ebola, SARS and, of course, new strains of flu. So what we're seeing today isn't necessarily unusual; diseases have emerged continually throughout history, flared up in an epidemic as more and more people came in contact with them, then subsided again as susceptible people died and survivors developed immunity. But better diagnostic techniques are identifying diseases for the first time, and increased global travel is helping spread diseases faster than ever before. The outbreak of the SARS virus in 2003 spread from China to Canada in a matter of days.
An epidemic is an outbreak of disease that attacks many people at the same time. Sometimes an epidemic lasts just a few hours, or a few weeks. But it can last several years. If it stays in a region indefinitely, it is said to be endemic. If it spreads around the world, it is said to be pandemic. In the past, only outbreaks of infectious diseases such as measles and flu were described as epidemic. Now the increasing incidence of non-infectious diseases like cancer and heart disease is often referred to as an epidemic, too.CHAPTER 3
What is a Virus?
'Virus is a Latin word used by doctors to mean "Your guess is as good as mine.'"
If you go to the doctor with a bad chest infection or diarrhea, the chances are you will be given an antibiotic, just in case the culprit germs are bacteria. Often, though, the antibiotic will have no effect, because the germ was, in fact, a virus. Because they often give similar symptoms like this, bacteria and viruses are often lumped together. Yet they couldn't be more different.
Viruses are a form of life like no other. In fact, there are scientists who say that they're not a form of life at all. Indeed, bacteria have more in common with humans than they do with viruses. For a start, both bacteria and humans and all other living things - have cells, microscopic parcels to contain their life processes. Viruses, uniquely, have no cell. They don't even have the cell structures that living things need to eat, make energy, grow and so on. All they can do that is lifelike is copy themselves. They are actually lifeless, inert chemical particles - as long as they are outside a living cell. Once they get inside a living cell, however, they change completely, taking it over like some demented house guest. Unfortunately for us, they are programmed to do just that.
All viruses have a core of nucleic acid coated with protein, and occasionally an envelope of fat. But this envelope is no more like a bacterium's cell wall than a paper envelope is like a house wall. The size difference is pretty similar, too. Bacteria are, on average, a thousand or more times bigger than viruses. While you can see most bacteria under a powerful light microscope, you need an electron microscope to see viruses. The Dutch microscopist Anton van Leeuwenhoek saw bacteria, or animalcules as he called them, back in the 17th century, but it wasn't until the 1970s that scientists had microscopes powerful enough to see viruses.
The virus's protein coat or fatty envelope is its safe-breaker, and its task is to get the virus into the cell. However, it must be the right cell. The viral coat of each kind of virus needs to match exactly the chemical receptors on its host cell. The cells have these receptors for obtaining the chemicals they need, not for viruses - but if the virus's coat finds a receptor that fits perfectly, it's in.
It's this need for a perfect match that makes viruses far more choosy about who they attack than bacteria. Most viruses live in the cells of a particular species of animal, and often a particular kind of cell within that species. The hepatitis B virus, for instance, targets primarily liver cells.
Once it finds its match, the virus penetrates the cell and begins its work. In an acute viral infection, the virus is not just an uninvited house-guest; it is a pirate. As soon as it enters the cell, it commandeers the cell's own machinery so completely that the cell becomes a virus factory. It's no accident that the term 'virus' has been adopted for computer software infiltrators, for viruses are very much like pirate software, taking over the cell's central processing unit and turning the cell's hardware to its own use.
Different viruses do this in different ways, depending on the nucleic acid in their core. Nucleic acid is the programming material of the living world. Deoxyribonucleic acid or DNA is the amazing thread-like molecule curled up inside every living cell. The sequence of chemicals called bases along its enormous length is actually a code for making particular proteins. This code can be the instructions to make an entire new organism - the DNA in every human body cell is a copy of the program for a whole new human being. Or it can be the instructions to carry out the day-to-day tasks the cell needs to perform. Making a whole new organism involves the whole of the DNA molecule, but for day-to-day programming, the cell merely makes copies of appropriate short segments on a simpler form of nucleic acid, called ribonucleic acid, or RNA, or rather messenger RNA (mRNA). That way, the precious DNA is not subjected to everyday wear and tear.
The nucleic acid in viruses can be either DNA or RNA, but never both. DNA viruses, like the herpes virus, make an mRNA copy of themselves using the cell's materials. This viral mRNA then takes over the cell's protein-making machinery to build viruses. RNA viruses like flu and polio can use their own RNA to build viruses directly.
With nearly all life-forms and even most viruses, DNA is always copied to make RNA, never the reverse. But there is one group of viruses that does the opposite. Called retroviruses, they copy their RNA into DNA. It's this DNA copy that is used to make the mRNA that instructs the creation of new viruses. The HIV/AIDS virus is a retrovirus.
So, in essence, once a virus has entered a cell, it takes over its machinery to make countless new viruses. This whole process is very rapid in the case of acute infection. Within a few hours, the infected cell is stuffed full of viral particles, ready to break out and infect others.
Sometimes, the viral particles simply burst out of the cell, destroying it in the process. This is why your nose and throat feel sore during a cold, as destroyed membranes peel off. In other cases, however, the viral particles emerge more gently in a process called budding. In this, the virus leaves wrapped in a bit of the cell's membrane. While in the process of budding, though, viruses are on the outside of the cell, like flashing beacons telling the immune system that here is an infected cell that must be destroyed for the good of the body. If it escapes destruction, the cell can go on shedding viral particles for ages, as happens in people who are 'carriers' of hepatitis.
The virus can even lie quiet in the cell, not making new viral particles - nor even causing any symptoms in the host. It may flare up every few years like the herpes virus, or not at all. Scientists are now certain that all of us have viruses lurking in at least some of our body cells all the time. There is a theory that viruses may even be major agents in the evolution of species, and that junk DNA (the apparently 'useless' portions of a DNA molecule) are the leftovers from past viral infections which have infiltrated their genetic material into that of the species they infect.
In recent years, a whole range of frightening virus diseases have emerged in the tropics, including the Ebola virus, Lassa fever, Dengue, West Nile virus, hantavirus and, worst of all, HIV. All these viruses are almost certainly not new, but have been brought out of hiding by some change in human activity. The belief is that these viruses are all linked to the destruction of the rainforests. As the trees are cut down, the animals that lived in them are forced to find new homes. As they do, they take with them viruses into close proximity with humans, or animals that are close to humans. It may be that the emergence of deadly flu strains has something in common with these.
Excerpted from Bird Flu by John Farndon. Copyright © 2005 John Farndon. Excerpted by permission of Red Wheel/Weiser, LLC.
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