Horizon (1964) s00e58 Episode Script

Pandemic - A Horizon Guide

This is the story of one of science's most significant encounters.
Pandemic disease borne by infectious bacteria, viruses and parasites.
NEWSREEL: 'Is man to be defeated by something he cannot even see?' It is a story played out in an era of unprecedented technical change, in which new scientific advances have given us the tools to confront some of natures greatest threats.
' And where shifting national rivalries have shaped their implementation.
We have seen every one of our worst predictions confirmed.
Many of us felt like Cassandra who could see the future, could speak the future, would be listened to, but would not be believed.
It is also a story of the television age, where each new wave of the disease reflects the changing nature of reporting.
We've gone from 1,000 to 2,000 to 4,000 cases in just the course of a month.
Science's battle with pandemic disease is an ongoing power struggle.
Since its advent, television has been there for every success and failure.
'Across the world, governments are taking emergency measures to try to contain the spread of swine flu.
' One in three people in the UK could become infected.
Swine flu has spread rapidly since it arrived here from Mexico.
In March 2009, a new form of the H1N1 virus, called swine flu because of its similarity to a virus found in pigs, put the globe under the latest threat of a pandemic.
In the last week, the number of cases has more than tripled.
There will be more cases, and more deaths.
It can no longer be contained.
It's in the community and spreading, and it's here to stay.
As a virologist, H1N1 shows all the sinister hallmarks of a pandemic.
It's caused by a virus that's new to humans and to which we have no immunity.
It can cause serious disease and is transmitted from person to person over a widespread area.
Today, we are better equipped than ever to deal with such an outbreak.
It is precious knowledge that has been hard won.
Swine flu is just the latest in a long line of pandemics from smallpox to SARS.
Outbreaks that can spiral around the world at ferocious speed.
This is the story of these diseases seen through the lens of over 40 years of Horizon and BBC television.
Although bacteria had been understood for centuries, it was the advent of electron microscopy in 1931 that allowed us to see a virus for the first time.
If I prick my finger, like that It was the beginning of a relationship between discovery and communication.
Television made visible what science could see.
droplet of blood gradually forming on my finger.
It would go on to chart every major scientific advance, and it was during this timeframe that we would learn more about disease than in our entire history.
And it was just as well.
In the mid-20th century, deadly microbes were one of the greatest threats to human health.
Poor sanitation during the Second World War drove the reign of infectious disease.
The need to conquer illness sparked a burst of scientific creativity.
Resources were pumped into the newly-formed NHS and the development of antibiotics and vaccines.
There was a new war to be won - the eradication of disease.
'Instead of tanks and aeroplanes, they fight with microscope and test tube.
'In their hands, victory and life.
'Not death to the invading Nazi, but death to the insidious microbe.
' In the decade after the war, television developed interest in this fight for public health.
'The world is ours, or so we like to think.
And why not? 'Haven't we worked to make it ours? 'Aren't we secure in our mastery? 'We like to think so, but this flask denies us, for its contents could strike us down in thousands.
'No, it is not a new type of bomb.
'It is the smallest creature in the world, a virus.
'The invisible enemy.
'Is man to be defeated by something he cannot even see? 'Are we winning, or losing?' The World Is Ours set the dramatic tone that would characterise many of the programmes that followed.
And not without reason.
This was a generation still in the grip of polio.
This water-borne virus attacked the nervous system causing disability, often leading to death.
'500 cases, 1,000 cases, 1,500 cases, '2,000 cases.
'2,300 confirmed cases of poliomyelitis.
' At its peak, 8,000 people were infected a year in the UK.
My grandad was disabled by polio, and I grew up being shocked at how the effects of microscopic viruses could be so devastating.
But by the mid-1950s, scientific optimism was paying off.
Would this vaccine at last wipe the disease from our world? A new polio vaccine was showing that science was able to successfully overcome disease.
A big step forward has been taken and we are confident that eventually poliomyelitis will be controlled by vaccination.
Television celebrated this early triumph.
Yet despite the progress, science's understanding of viruses remained rudimentary.
Horizon took a detailed look at the challenges organisms were posing.
'Viruses can only grow in a living cell.
' They can't produce all their building blocks for themselves.
They have to be parasitic on the building blocks, nucleic acids etc, of the cell.
The virus has to enter the cell before it will grow and, in many respects, it's therefore protected by the cell and it replicates in the cell.
It's only when it destroys the cell and the cell bursts, all these many virus particles come out to infect more cells.
That's how the process of virus replication goes on.
And the only way in which you can attack it is to destroy the building-up process of the virus.
To do this without destroying the cellvery easy to give a poison to man that would kill the virus.
It might kill the man as well.
Because attempts to kill the virus could be harmful, the emphasis was on finding safe vaccines.
I think every country or area ought to have at least one laboratory which is capable of, at very short notice, taking on the investigation of a dangerous infectious disease which appears because, from time to time, they're going to emerge and you want to examine the problem and find out what you can do.
'In laboratories we visited all over Britain, we've also seen dramatic work on flu, as well as rabies, 'on hepatitis as well as the hundred manifestations of the common cold.
'And the new and improved vaccines we've seen are only the first results of this.
'Despite the unknowns, there's a strong feeling of optimism, of excitement at the rate of progress.
' It never stops.
We began with the easy ones.
After that, we had problems, because our techniques were not sufficient to show the viruses which we knew were there.
We had to find new techniques to identify them, to show that they were there.
It's most certain that new techniques will provide new openings for new vaccines.
I'm very positive.
But with experience came caution.
The long-term effects of vaccines were still unknown and contaminated supplies had infected many of those they sought to protect.
The important thing to make sure is that the risk of the vaccine is not greater than the risk of having the disease.
This is the important thing, that the risk is worth taking.
At the same time, the need for mass vaccination was taking off.
The global population was multiplying.
Packed cities became breeding grounds for disease, and travel - the perfect carrier.
'It's only a matter of time before some exotic virus disease reaches Britain by intercontinental jet.
' We had entered a new world, and so too had disease.
And it wasn't just viruses taking their toll.
In the 1970s, the world was in the throes of a cholera pandemic, a deadly bacterial intestinal disease indigenous to the Indian subcontinent.
It was carried by contaminated food and water and spread by trade routes.
By 1973, it had reached Italy.
In the UK, it was making the news.
'The disease is one of the most contagious in existence.
'Even vaccination does not give 100% protection.
' - Do you think all cholera cases are reported? - No, not by any means.
It's an iceberg disease.
Most cholera is probably relatively mild.
It goes off as an attack of diarrhoea, and it's only when there are a lot of serious cases that it comes to note in the way in which it is now.
When the tip of the iceberg gets, as it were, higher out of the water, we think there's an epidemic.
Cholera was seen as a disease of poverty and industrialisation but, within nine years, it had been reported in 93 countries.
To this day, it has yet to be eradicated, and a new strain of the bacterium is enjoying what is feared to be its latest pandemic in 11 countries.
The West's close contact with disease raised questions about the responsibility of richer nations to the developing world.
Horizon was early to engage in this ethical question.
We do ignore the health of the Third World at our own peril.
It will come back to haunt us.
The virus that felled a child in a distant village yesterday can reach your own family today and be the seed of a global pandemic tomorrow.
The will and resources to treat disease became part of a global political issue.
And there is one pandemic that epitomises this more than most.
Throughout history, malaria has killed more people than any other disease.
It's caused by the plasmodium parasite and is spread by infected female anopheles mosquito bites.
Its microscopic size belies its devastating impact on human health.
Horizon repeatedly reported efforts to combat the disease.
and in 1982 took an unflinching look at its impact in Sri Lanka.
HE GROANS 'Untreated, this man could expect convulsive shivering 'and then a high fever every two days for several weeks.
'Then later, he'd be likely to have relapses.
' Malaria can also cause brain disease, anaemia and kidney failure, and still kills one million people a year.
The first attempts to combat the disease were triggered by a different type of conflict.
The US military were losing more soldiers to malaria than bullets in tropical war zones.
So in the Second World War, they set out to develop a powerful insecticide and came up with a breakthrough - DDT, a substance that destroyed the nervous system of mosquitoes.
In 1955, the World Health Organisation, the new global disease watchdog, used DDT to launch the world's first disease eradication campaign.
Its aim - to wipe out malaria by the 1990s.
It seemed to be working.
Malaria was eradicated from North America and controlled in Southern Europe, Asia and Latin America.
In Sri Lanka, cases dropped from almost three million to only 17.
Victory seemed to be in sight.
'Our children will be the first generation freed from the enslaving fever.
' But science was up against a formidable enemy evolution.
Mosquitoes breed at a rapid rate.
With each generation, comes the possibility of genetic mutation.
Over time, mosquitoes build up resistance to insecticide.
In 1969, the World Health Organisation gave up its fight.
The worldwide eradication plan had failed.
When the spraying was stopped, the mosquitoes returned with a vengeance.
Having thought malaria had been wiped out in Sri Lanka in 1962, it was back.
17 years later, scientists around the world started work on the ultimate dream - a vaccine.
Progress in Sri Lanka was such that Horizon also reported on an experimental procedure under way.
'These poor creatures are less fortunate than their human benefactors 'for this troop of animals is heavily afflicted with malaria.
'These monkeys have a completely separate parasitic strain 'uniquely designed to invade their own body cells.
'In the path toward a vaccine, monkeys are close to man, 'but are safe for human researchers to try ways of making vaccines work.
'They need the help of this woman and her cow 'to attract and trap the other half of the monkey malaria system.
'The job of the cow is to act as captive bait, to lure in a mosquito called Anopheles elegans 'so that, in the night, when they're biting, the campaign's entomological teams can steal in to collect them.
'All the mosquitoes want is a blood meal 'and even then, if they do carry malaria, they can't infect the cow, so everyone else is safe.
'When vaccines are developed, they will have to be tested against animal malarias.
'Could this be the beginning of the end for human malaria too?' But like eradication, attempts at a human vaccine failed.
The only hope of controlling the disease was with antimalarial drugs.
In China, there had already been a breakthrough.
A drug, Artemisinin, derived from an ancient plant was showing promise as a treatment.
But it sparked huge scientific rivalry between the East and West.
It wasn't until 2005 that Horizon was able to examine the truth of what happened.
TRANSLATION: The foreigners seemed to be snooping.
They were so arrogant and contemptuous.
They were astonished that we Chinese had managed to achieve this amazing breakthrough when they'd spent so much time and effort on it and failed.
Communist China was reluctant to share its discovery with its Cold War enemies.
Particularly as members of the WHO committee responsible for anti-malaria drug development were members of the US military.
China refused to release the plant or the drug to the rest of the world.
15 years after its discovery, the drug was still unavailable to millions who needed it.
It was very frustrating in the 1980s because here was a promising compound that many people wanted to work on, but yet we couldn't get it.
It wasn't being sent out of China.
It became clear that we needed another source for the compound.
The new goal was to develop synthetic replacements.
After years of trials, the artemisinin family of drugs became the world's frontline defence against malaria.
Political divides had wasted time, but the ultimate weapon was still prevention.
And there was increasing optimism about developing a vaccine.
Horizon also followed an experimental trial in Mozambique which was showing promising results.
'A vaccine that gives full protection against malaria is still some way off, 'but it's no longer seen as impossible.
'More than a dozen teams around the world are now chasing this great prize.
' Does that mean we have a vaccine today? No.
But it means that we're absolutely sure that it's possible.
We just need to figure out the timing part of it.
'In the meantime, Artemisinin, the Chinese wonder drug born of Cold War politics, 'holds out the promise of a cheap, effective cure.
'For the first time in a generation, science has delivered 'an effective weapon to once again declare war on malaria.
'It's a war that many scientists now believe we can win.
' Yes, we can eradicate malaria.
It's not going to be easy, but it can be done and we have the tools now to do that.
Science appeared to be winning the war against nature.
But in May 2009, television broke news of its latest defeat.
Scientists say they've uncovered the first evidence that malaria spreading parasites are becoming immune to the world's most effective drug for treating the disease.
The scientists say the resistance, discovered in Western Cambodia, has to be urgently contained because its spread could lead to a global health catastrophe.
Despite its impact on human history, malaria has received only scant attention.
Without effective treatment, the death rate could double in the next 20 years.
We assume pandemics will have a beginning and an end.
But few fit the model.
In the 1980s, a new threat emerged, the scale of which would take years to realise.
It first hit gay men in America who developed unusual diseases that didn't respond to treatment.
GRID, or Gay Related Immune Deficiency as it was known, represented a potent brew of sex, death and sexuality.
Horizon was the first British television programme to uncover the story of what would become known as AIDS.
In 1983, Killer In The Village, followed science's first steps in understanding this new disease.
The trail began in a leading American disease centre where a spate of similar symptoms had been causing alarm.
'It was this rare pneumonia that first alerted the Centres for Disease Control in Atlanta, Georgia, 'that something very odd was going on.
'Usually, it's people like transplant patients, whose immune system is artificially depressed, 'who sometimes get the pneumonia.
Sandy Ford controls all supplies of the best drug for it.
' I need your patient's name, age, sex, weight and the underlying reason for the immunosuppression.
'In 1981, there was a sharp increase in the number of requests.
' There's no underlying reason for the immunosuppression.
'The drug is restricted and she's supposed to have a clear diagnosis.
' He's not on chemotherapy for any malignancy? 'Just checking.
Chemotherapy also hits the immune system.
'When this first happened, all she could think about 'was her uncompleted paperwork, but then it happened again, and again.
'In a matter of months, the unsatisfactory forms began to pile up.
'The requests came mostly from around New York and from Los Angeles.
' How about WBC count? 'White blood cells.
' - 2,000.
- 'That's low!' There were other outward signs that something was seriously wrong.
'Bobbi Campbell, a nurse in San Francisco, was one of the earliest AIDS victims still alive.
'On a walking holiday he'd found what looked like a blood blister on his foot.
'It didn't clear up so he showed it to a dermatologist who took a biopsy and diagnosed Kaposi's sarcoma.
' I was devastated.
I was 29 years old and I had cancer.
I had a cancer that had killed a number of gay men in this country and some other countries.
I felt like my death might be imminent, even though I felt fine.
In the year since I've been diagnosed, three people that I know personally have died and each time it's a blow to the heart.
'Pneumonias in LA, some cancers in San Francisco, both in New York, and all, it seemed, were gay.
'Homosexuality has been around since ancient times.
'But AIDS is new.
So, why is it here? 'Why now? And why them? 'Is AIDS infectious? Can anything be done to stop it? 'Can AIDS be cured?' As we gathered more and more patients, those patients would meet each other in the office.
It became apparent that many of the patients had had contact with one or two, or perhaps more, other people who had the syndrome, which began to suggest to us that perhaps there was a sexually transmittable a single sexually transmittable agent that was being passed around in the community.
Science was grasping at the possible causes of infection.
Our most exciting hypothesis, and the one that we are working on most, is that, with the multiple exposure to sperm that homosexual men have from a variety of sources, both through the rectal route or through the oral route, and possibly absorption through the mucosa, that sperm is able to penetrate into the immune system or into the blood.
'The most obvious public health message has been to avoid sexual contact 'with anyone suffering from or even suspected of having AIDS.
But since the disease may be hidden, 'and casual, anonymous sex is still readily available 'in many American cities, 175 gay doctors have endorsed this advice.
'And all this applies to Britain too.
DISCO MUSIC PLAYS 'There is a great deal of travel between the world's gay communities.
'A year ago, few British cases had been recorded.
'Now, they number 40, with 22 dead.
'Which means hundreds more with the complex.
'The AIDS epidemic has a foothold here.
' Whilst Horizon kept strictly to the science story, other coverage reported the social fallout.
I don't like homosexual practices at all.
I think it is a Godforsaken, unnatural, unhealthy, disease-ridden occupation.
The AIDS virus has given us yet one more reason for wanting to minimise the amount of homosexuality in society.
As a high proportion of AIDS victims are homosexuals, shouldn't homosexuality be made illegal? The only prevention is the castration of all homosexuals to avert the spread of this disease.
The homosexual act is unnatural.
It's perverted and it's incredibly filthy.
Against this backdrop of homophobia, science continued to search for answers.
I would like to ask Dr Gallow to come forward.
In May 1984, an announcement by the United States Health Secretary made the headlines.
There is, of course, important news.
The probable cause of AIDS has been found.
With the discovery came the hope that a cure was just round the corner.
process will enable us to develop a vaccine to prevent AIDS in the future.
We hope to have such a vaccine ready for testing in approximately two years.
Approximately two years.
In 1986 there was still no vaccine and in AIDS - A Strange and Deadly Virus, Horizon explained why.
'The AIDS virus is one of the simplest life-forms on the planet.
'It belongs to an unusual family called retroviruses, only recently discovered to infect humans.
'Within its spiky outer shell, is a protein core that protects the virus' genetic heart.
'These foreign genes can pirate the cells that they infect.
The viral genes are permanently inserted into the normal cellular DNA of the infected cell of the particular person that got infected.
So that infection of that cell is forever because the viral genes are now part of the cellular genes, integrated right in.
This integration occurs when the short chain of virus genes meets the DNA of the infected cell.
The human cell is taken over.
Sometime in the future, the inserted genes will make copies of the virus.
Not only is that cell infected for a lifetime, when that cell divides, the daughter cells will also have not only the cell genes, but also the viral genes, so infection of the person is forever.
The increasingly widespread transmission of the disease raised questions about whether this WAS a disease of homosexuality.
'It's in Africa that the AIDS pandemic is at it's most acute.
'It's hard to believe that homosexuality or drug abuse 'can account for the millions infected with the AIDS virus there.
' I have become more convinced than I was before, that AIDS in Africa is transmitted principally by sexual contact.
And principally by heterosexual contact.
There may be other factors such as the re-utilisation of hypodermic needles that haven't been properly sterilised and some people have said perhaps insects, biting insects like mosquitoes, might spread the virus.
But the one thing that has come through loud and clear is that AIDS is spreading in the most sexually active people in a community and particularly amongst the promiscuous.
Mosquitoes and needles do not select between those people so very much, so I think it still comes down to saying if you want to avoid AIDS, avoid having too many sexual partners.
Despite a promising drug called AZ and experiments in animals to find a vaccine, the virus was fighting back.
'Just like influenza, it seems the AIDS virus can mutate 'to evade the body's defences.
'The protein spikes are what count in the immune response.
'Key points on the surface of these proteins are recognised by the antibodies.
'By mutating at precisely such places, an extremely small change 'in the virus can defeat antibodies produced both naturally and by a vaccine.
'Antibodies made to the old configuration no longer bind, 'and the virus can stay one jump ahead of the immune system.
'And there's a second reason to doubt a vaccine will work.
'The AIDS virus can escape detection by the immune system 'if it enters the body inside a cell from another person.
'This foreign cell is then engulfed by a scavenging, 'slug-like macrophage, and so, the AIDS virus passes 'directly from the cell to cell, bypassing any antibodies in the blood.
It seemed that the virus could outwit even the most cutting edge science.
We're in the presence of an epidemic for which we have no vaccine and no effective treatment.
That's as simply as I can put it.
More than 20 years on, the hunt for an effective vaccine has failed.
We now know that AIDS is much more than a sexually transmitted disease.
Whilst antivirals may slow its progress, they can't stop it.
We've since learnt that HIV exploits its ability to mutate, more than any other virus.
Untreated, HIV makes 10 billion new virus particles in one person in one day.
Coupled with its high mutation rate, it means there are many variants of the virus.
More than any single vaccine can contend with.
Since Horizon's first contact with AIDS, it's killed over 25 million people worldwide, making it one of the most destructive pandemics in history.
Few pandemics present such a challenge.
Thanks to a combination of global cooperation and some centuries-old science, we were able to halt one of history's most feared diseases.
The cause is in this container.
The world's most violent killer.
The smallpox virus.
Unlike HIV, the Variola virus that causes smallpox barely mutates, and in the 18th century scientists were able to produce the world's first ever vaccine.
200 years later, the WHO had a bold plan - to vaccinate every single person at risk.
All billion of them.
In 1997, Horizon celebrated this extraordinary feat and went to meet the scientist behind it all.
I felt overawed by the task ahead, recognising we had so many languages to deal with, that we had so many different countries to deal with.
We were dealing with countries where there was famine, where there was war, wherever it was, whether there was even organised civil government there, we had to go.
There were many scientists who said that this was just not possible to do.
In fact, at the time, even the director-general of the WHO, said, it just can't be done.
In a phenomenal effort, a team of hand-picked doctors worked tirelessly to vaccinate or treat every case of smallpox.
Having vanquished smallpox in Ethiopia, India, Bangladesh and every other country, the searchers were on the trail of the very last strain in Somalia.
They tracked the virus to this village.
And then to this woman who had infected her two babies.
One died, but this child survived.
They traced all her contacts, and that is when they found him.
Ali Malin, the last person on the planet with smallpox.
He survived.
We reached the point where we had found the last case, and eight weeks had gone by, there were no more cases, nobody could find anything, we suddenly realised that it was over.
It was deemed a public health miracle.
By 1979, smallpox was the first infectious disease to have ever been eradicated from the wild.
Millions of lives had been saved.
The virus was so dangerous, that stocks of it would only be kept in two WHO approved laboratories in America and in Russia, after which they would finally be destroyed.
During the 1980s, it became clear to everyone that there was a building pressure on the part of all countries to come to the end of this programme and draw a line with the destruction of the virus.
So the US scientists and Russian scientists who at that time had the virus, worked out a series of steps to be taken to make sure that we had characterised the virus as carefully as we could and a total DNA map of the virus began to be constructed.
It was decided that this could all be done by the end of December 1993.
1993 arrived and the work wasn't completed.
The decision to destroy the stocks was postponed because something extraordinary happened.
When scientists compared the genes in the pox viruses to those in gene banks they found genes in common with our own.
What became clear is that within these genes were instructions that seemed to have been hijacked from the host immune response.
In other words, these viruses were mimicking the host.
They had stolen components from the immune and inflammatory response, and this was really an astounding realisation, a new level of complexity, something none of us were prepared for.
When cells are invaded by a virus they send out warning signals which lock onto receptors on the healthy cells around them and give instructions to protect them from attack.
Amazingly, the pox viruses steal our genetic information and manufacture their own decoy receptors.
So the messages directed at the healthy cells are swept up by the virus' fake receptors and the warning never gets through.
There was a dawning of recognition that these beasts had tricks that we had never seen before and it was sort of a thrilling time.
With this growing list of discoveries, it dawned on the scientific community that the virus understood us better than we understood ourselves.
Scientists now began to feel that the smallpox virus might be too precious to destroy.
If we could study the virus to learn how it gained control of our immune system, we might be able to unlock clues to other viruses and ultimately cure ourselves.
We're looking at a whole new way of treating disease.
I think these viruses have illustrated for us, the principles of decoy receptors, the principles oftinkering in subtle but clever ways with the host response.
And I think they are leaving the way to showing us whole new ways of making drugs and treating disease.
Over at the high security laboratory in Siberia this idea has caused excitement.
TRANSLATION: We can synthesise individual proteins and use them for future pharmaceuticals.
The smallpox virus is an outstanding example of this.
It could be used to treat severe diseases that are now virtually untreatable.
Such as septic shock, cerebral malaria, rheumatoid arthritis, acute AIDS-related conditions and so on.
And this is what we are working on now.
There are many more genes that we have yet to study in the smallpox virus.
Each of which might lead to new drugs.
But there is something more.
These genes may tell us how all other deadly viruses attack us.
Because smallpox uses every trick there is.
On May 24th 1996, WHO gathered to decide finally the fate of the smallpox virus.
TRANSLATION: If WHO decides to take this fateful step and destroy such a unique subject for research as the smallpox virus, it will confirm to me that the world isn't ruled by reason, but by bureaucracy and politics.
Ladies and gentlemen, are there any comments on this? I see none, then the resolution has been approved.
APPLAUSE On June 30th 1999, all the stocks of smallpox will be destroyed.
And research on the live virus will end forever.
The stocks weren't destroyed.
And what they tell us about killer viruses is still being used in a hunt for the AIDS vaccine.
But smallpox was spared for a different reason.
After 9/11 the world changed, and the virus could be used as a lethal weapon by bioterrorists.
Scientists needed to understand the virus to protect our global security.
But, to my mind, the boundary between fear and the true threat of disease was blurring.
We had entered a new digital age in which internet rumours and rolling news spiralled fear of the next pandemic.
By 2002 the world was poised for global attack.
They are struggling to contain the epidemic.
We've gone from 1,000 to 2,000 to 4,000 cases in just the course of a month.
And a new threat did emerge.
Not from bioterrorism, but from nature.
SARS is the story of the modern plague.
A virus that seemed to come from nowhere and spread panic throughout the world.
It began when a life-threatening pneumonia, Severe Acute Respiratory Syndrome, began to spread through China.
It was declared a bigger threat than AIDS, heralding a rapid hunt to track down the cause.
By now, science had a new weapon in its armoury - rapid genetic decoding.
Horizon recounted the steps science had taken to contain this emerging threat.
On the 15th March, the WHO announced a worldwide alert.
This was something the WHO had never done before.
The alert meant the mystery virus was now declared an official threat to everyone on the planet.
We had to react to an urgent public health need, so we were all very worried and we knew that this was a race against time, so we had to find very quickly, the pathogen, the causative agent for this disease.
All the labs had agreed to forgo their rivalries and collaborate.
For the first time in history, the full force of the world's scientific might was united and focused on identifying just one disease.
But as the detective work progressed, the disease continued to spread.
By the 20th March, 306 people around the world were infected.
And a disturbing statistic was emerging.
SARS killed about 4% of its victims.
One in 25.
But then came more encouraging news.
There was a breakthrough in the hunt for the cause of SARS.
A team in Hong Kong had isolated a virus from a SARS patient.
Using a technique called random polymerase chain reaction, scientists then tried to identify this virus.
They took tiny strands of DNA from hundreds of different known viruses and began testing them, one after another, to see if any of them matched the mystery virus.
They struck lucky.
The normally benign virus they identified was more often known for the common cold.
But it's also carried by animals, which in China live side by side with people.
If the virus mutates, it can make the deadly leap to humans.
These viruses that jump across from animals to people can be utterly lethal.
Our immune systems are simply unprepared for the threat of the new.
It's how most killer diseases come into existence and it may well be how SARS was unleashed on the world.
On the 12th of April, just 20 days after the discovery of the SARS Corona virus, a team in Canada announced they'd cracked the virus's entire genetic code.
Never in the history of science has a new disease been sequenced so quickly.
We've been able within four weeks to detect the culprit, to nail it down, to sequence it.
I have never seen anything like this before.
It's been staggering how quickly we're moving.
It could be a huge step towards designing a cure.
Already the genetics has thrown up some hopeful news.
The virus is barely mutating at all.
It is virtually the same from Hong Kong to Canada.
That means it should be easy to design specific drugs for it, as unlike the virus causing AIDS, it's not a rapidly moving target.
From what we know so far, it looks as though the virus would be stable enough that vaccine development is a viable option.
In the meantime, with intimate knowledge of how the virus spread, scientists came up with a strategy to contain it.
A simple one.
Mass quarantine and infection control became the most effective ways to defeat the disease.
All over the world, countries coordinated their fight back against the disease.
It really is a good news, sort of tingly, human story.
Seeing the world, which is often so fragmented, pulling together to try and fight this common cause.
They managed to arrest the virus and the last case was reported in May 2004.
SARS claimed just 800 lives worldwide, whereas 5,000 people die from flu each year in Britain alone.
Human trials for a vaccine are under way, should a SARS pandemic ever return.
The success of halting SARS reminded us of both science and the power of global cooperation.
It was to be a dress rehearsal for an even greater fear that was lurking just around the corner.
In 2003, we faced another deadly threat.
The H5N1 virus, or bird flu.
Science had moved on and our knowledge of viruses meant that we no longer had to wait for a disease to go pandemic to imagine its hypothetical future.
This was the science of prediction and it wasn't long before television followed suit.
In a departure from the norm, Horizon merged drama with science to present a fictionalised account of science's worst case scenario.
We're talking about a massively increased number of deaths per day over what we would normally see.
That would be happening everywhere.
We will very quickly overwhelm our mortuaries, our morgues, our funeral homes and our cemeteries.
Our schools, which are places of laughter and life, will become morgues.
Families, where everybody's sick and the mother or the father can't even take care of the child, I think that's so foreign to our concept of life, that we can't imagine it.
The basis for this fearsome scenario was the fact that H5N1 a virus found in Chinese bird flocks, had in a few instances made the deadly leap to humans.
This particular H5N1 virus, falls into the category of what we call a highly pathogenic virus.
When we analysed it, we found a tiny extra piece of genetic material that's in one of the genes of the virus.
This very small change allows the virus to spread beyond the respiratory tract.
Many of these people who have become infected with H5N1 are dying from multi organ failure.
For this hypothetical pandemic to become real, the virus would have to undergo further mutation, one that would enable human-to-human transmission.
This H Protein right now cannot attach very easily to human cells and cannot spread from one human to another.
The best scientific estimate is that one or two mutations will be enough to allow this virus to attach easily to human cells HE SNEEZES When we cough or sneeze we'll easily transmit it to another human being, and it'll ripple through like a wildfire in the population.
When the scientists set their virtual flu virus free in the world they had created, the results were far reaching and devastating.
What happens is as the rate of infection increases, the colours change from yellow to red.
And you're starting to see hotspots here of masses of red dots, meaning that there's a very high incidence of infected people in those areas.
By the time we get to about three months in, the incidence of pandemic influenza reaches its peak.
It's no longer just in the major cities.
Basically, the entire country is experiencing a very severe outbreak.
In just three months, the entire country was overrun.
The sea of red dots leave very little to the imagination.
With a mortality rate of 60% for those infected, H5N1 bore many of the hallmarks of the most devastating disease episode in history.
The Spanish Flu of 1918.
At the moment with H5N1, 140 people have died in a population of six billion.
People come to me and say, "that's not many.
" But my answer to that is, go back to the year before 1918, there you had 140 people dead, but within a year it exploded and killed 50 million people.
So there's a warning there.
We can't ignore a virus that has done that in the past, we really can't.
If this H5N1 virus mutates to be anything like the 1918 virus, the number of new infections and deaths will double every three days.
I think until you believe that every tenth person in your community could die next month of a disease they have no control over, until you really believe that, how are you going to prepare for it? Thankfully, these worst fears have never materialised.
A pandemic of the scale imagined here is an extremely unlikely event.
Pandemics challenge our deep-seated belief that we are in control of nature.
Despite our technological advances, we still only successfully eradicated one disease, smallpox, from history.
Pandemics will continue to be a biological and mathematical certainty.
In the age-old battle between science and disease, it seems disease is still winning.