Bird Flu - WHO view on global threat

Futurist Topics - Health

Article Index
Bird Flu - WHO view on global threat
Page 2
Page 3
All Pages

 

Article about bird flu written in November 2005.

The Director-General of the World Health Organization (WHO) Lee Jong-Wook said on November 6th 2005 that the H5N1 avian influenza virus was spreading fast. "We have been experiencing the relentless spread of avian flu. Migratory birds, as they move around the world to seasonal breeding and feeding grounds, are infecting domestic poultry flocks around the world." He said it was only a matter of time before an avian flu virus, most likely H5N1, acquired the ability to be transmitted from human to human.

David Nabarro Bird Flu chief at the UN / WHO, declared in October 2005 that a human pandemic of bird flu can no longer be prevented, even though the first human to human case has yet to be verified.

However the REAL issue is not whether bird flu will jump successfully into humans in an infectious form, but how long it will be before we see a global pandemic of a mutant flu - from whatever origin - birds, pigs or whatever, combined with human flu genes.  Since such mutations occur at least once a year, WHO believes it can only be a matter of a decade or two before this happens.

This WHO prediction on bird flu in 2005 is based on the fact that the world has lost control of bird flu. Every time a human catches the infection from close contact with such a bird there is a small risk that the virus will mutate - if the person is already infected with ordinary human flu.

The US has committed $7bn to help prepare the country for what is being increasingly seen by the government as an inevitable major flu pandemic with high mortality - whether from a bird flu mutation or a totally new new viral type. "The only question is when."

US worst-case estimate is anywhere between 200,000 and 1.9 million deaths with 92 million others becoming ill. The government annnounced in early December 2005 that they had modelled a theoretical outbreak of human to human bird flu in Thailand, which produced an estimate of up to 722,000 cases just 6 weeks later across America, rising to 92 million cases just 10 weeks after that. Clearly spread at such speed would overwhelm health care systems, and would happen too fast for vaccines to be prepared and given.

A moderately severe pandemic on the scale of the 1968 pandemic, adjusted for the growth in US population, would cost the US economy $180bn not including business disruption.

The UK government has declared bird flu as public health enemy number 1. It has given a commitment to try and vaccinate the entire population of the country against the new human variant once one emerges, even though spread of such a virus could occur months before vaccinations are manufactured and given.

The World Health Organisation has warned repeatedly of significant risks to global health from new mutant viruses - of which HIV, SARS virus and Bird Flu virus are three of many examples we have seen. I have also warned about these risks since 1987, in most presentations to corporations and also in the books Futurewise (1998/2003) and The Truth about AIDS (1987/2004).

Just one of these is the form of Bird Flu caused by virus H5N1. In mid April 2005 the Viet Nam Ministry of Health reported to WHO that 41 cases from 18 cities and provinces had been detected in since mid-December 2004. Of these cases, 16 had died and six remained under treatment. By October 17th 2005 there had been 117 human cases of which 60 had died. By mid December 2005 the numbers reported had risen to around 150 of which half had died, with growing concerns about the possibility of many other missed cases.

Human bird flu is usually only suspected when someone has a severe, unexplained flu-like illness, in an area where birds are dying rapidly. Mild cases are inevitably going to be missed, unless we start testing groups of other people for antibodies to bird flu. And outbreaks among birds can also be missed or go unreported, as was the case for more than 8 weeks in parts of Ukraine through the Autumn.

Possible Economic Impact of Bird Flu Mutation

A human influenza pandemic could cost the world's richest nations $550 billion, according to the World Bank (Report November 6th 2005).

Previous studies on flu pandemics have suggested any new outbreak could kill between 100,000 and 200,000 people in the United States alone, which could translate into economic losses for the country of between $100 billion and $200 billion. This estimate includes 700,000 or more hospital admissions, up to 40 million outpatient visits and 50 million additional illnesses. However, as we have seen above, the worst-case US government estimate is of up to 1.9 million deaths..

The World Bank has extrapolated from the US figure based on only 100,000 to 200,000 deaths, to all high-income countries, with a present-value total loss of $550 billion. The loss for the world would be significantly larger, because of the impact in the developing world.

The Asian Development Bank warned that the economic damage in the East Asia region from a pandemic could be as high as $282bn (£158bn), assuming 20% of the region's population falls ill.

A two percent loss of global gross domestic product during a pandemic -- like that caused by SARS in East Asia during the second quarter of 2003 -- would represent about $200 billion in losses in one quarter or $800 billion in a year.

The US. government has published its own report on the possible impact of bird flu mutations on the US economy. The health costs alone of a moderately bad pandemic, not including disruption to the economy, are estimated to be $181 billion. This figure describes a pandemic similar to that of 1968, which killed about 34,000 Americans, a figure close to the annual average of flu deaths now in a larger U.S. population. Yet the 1918 pandemic killed 500,000 Americans. Economic disruption, through travel limitations and a sharp rise in sick days, would be enormous. The US report predicts that a worst-case avian flu pandemic could kill from 209,000 to 1.9 million Americans. Outside estimates of a global toll have ranged as high as 50 million or 60 million.

Our world is very open to disruption by lethal mutant viruses because we still have no antiviral drugs that are as effective as penicillin and other antibiotics against bacteria.

The economic impact of an uncontrolled pandemic could be devastating to the global economy as a whole, if death rates are high, and the effects could last more than a year. Some kinds of business such as conferencing and tourism could be severely affected in some parts of the world at an early stage.

Impact is likely to be greatest on all activities which cause people to gather together, on travel and tourism, but also on parts of the food and manufacturing industries as well as other business sectors. It all depends on how many cases there are of a human form of the infection, where they are, what the death rate is and how infectious it seems to be, and what the public reaction is.

Some countries such as America have already indicated that they may close borders if a dangerous super-flu pandemic seems to be starting.

As we saw with SARS, there would only need to be a few thousand cases with a 10% mortality (bird flu at present kills 50% who get it) to cause major business and leisure disruption in different parts of the world. The cost to the regional economy of Sars was been estimated to be many billions of dollars. Despite this, in early November 2005 markets had yet to price Bird Flu risk into their forecasts and risk assessments.

The greatest factor is likely to be emotional: worries, uncertainty, fear, loss of confidence, with postponement of expenditure until the situation is more certain.

The British government by October 2005 was working on the basis of a million infections in the UK with 50,000 deaths - four times the normal annual death toll from flu - but with a contingency plan in case the death toll was more than ten times as high.

So long as business and consumers believe that a pandemic is just a worse version of the usual flu epidemic, it is likely that impact will be relatively small in the short term. However, playing down the risk could contribute to loss of control by making it difficult to justify radical control measures.

Government leaders may be faced with difficult choices: give clear, strong warnings and get effective control, at the risk of worrying millions of people and wrecking some industries - or play down the threat and just hope for the best.

If death rates are high in the first few thousands infected, it is likely that members of the public will start to change behaviour regardless of what governments say, and leaders may come under huge pressure to implement emergency measures such as closure of schools in some areas, and restriction of all unnecessary travel. Some scenarios could include closure of some airports. Indeed, Reuters has reported that the Chinese government will close all borders if there are proven cases of person to person spread in China.

We could see some control measures introduced because of the need to reassure public opinion even where experts believe such measures will have little or zero effect. Air travel is a good example. In 1918 some 300-400 million became infected in a few months without a single aircraft being involved. A country could try to seal all borders and still find it has a major epidemic - perhaps from unrecognised infection that has already arrived, or from unpreventable movements of people. We can expect vigorous debate about what is appropriate to do.

With every week that passes, our world becomes slightly better defended, as governments refine their infection control plans, stockpiles grow of antivirals, more aggressive efforts are made to slaughter infected birds, and more bird handlers are vaccinated against ordinary flu (to reduce risk of getting both infections and triggering mutations).

If (or when) the human mutation occurs, it will be vital so slow down spread for as long as possible in the early stages, so that the virus can be analysed, treatments tested, and vaccine production started on a massive scale.

Viral epidemics not taken seriously enough

As I pointed out in 1988 in The Truth about AIDS, and in 1998 in Futurewise, we continue to take risks by not taking viral epidemics seriously enough in terms of medical research. As a physician who has been involved in the fight against AIDS for more than 17 years, it is shocking to look back and realise that we are hardly any further forward in treating viral illness like flu than we were back in 1943 when penicillin first began to be available, and 1944 when effective treatment began for TB, syphilis, pneumonia and a host of other conditions. It is true than new antivirals are prolonging life in those with HIV, but these drugs are toxic, have to be taken until the person dies, and don't cure anyone. They just suppress the infection - and then usually only for a while.

AIDS has killed 45 million people in 20 years - and could kill 200 million more over the next 30. But flu epidemics can also be very dangerous - and far harder hitting.

1918 Spanish Flu killed 30-40 million people

In 1918 - 1919 a virus swept around the world that caused what became known as "Spanish flu". Over 18 months it is estimated that 400 million people became infected of which 30 million died - which is 600 times the number of Americans who died in the entire 10 year Vietnam War. 675,000 Americans died of Spanish flu, of which 200,000 died in October of 1918 alone. People often died very rapidly, and many of the victims were young - in contrast to normal flu which is most dangerous to the old.

"As their lungs filled . the patients became short of breath and increasingly cyanotic. After gasping for several hours they became delirious and incontinent, and many died struggling to clear their airways of a blood-tinged froth that sometimes gushed from their nose and mouth. It was a dreadful business." Isaac Starr, 3rd year medical student, University of Pennsylvania, 1919 commenting on flu deaths he saw

The 1918 global flu pandemic spread in the age of horse, boat and train - and at a time when the world population was only a third of what it is today. If such a virus was to re-emerge, perhaps as a mutation of Bird Flu, it could spread far faster, and kill up to 100 million people.

Reports in October 2005 suggest that the genetic profile of bird flu is almost identical to that of the 1918 virus - which has been obtained from the sample of a victim preserved in permafrost.

The work involved researchers from the Armed Forces Institute of Pathology (AFIP), the CDC, Mount Sinai School of Medicine, and the U.S. Department of Agriculture. Jeffery K. Taubenberger, MD, PhD, chief of molecular pathology at the AFIP, one of the study leaders, commented:

"These H5N1 viruses are being exposed to human adaptive pressures, and may be going down a similar path to the one that led to the 1918 virus," Taubenberger said in a news conference. "But the H5N1 strains have only a few of these mutations, whereas the 1918 virus has a larger number."

Our only real defence against viral illness like flu is the immune reaction we develop in response to infection. But if a flu virus changes shape as a result of a new mutation, our immune system fails to recognise it and has to develop a new response, which takes time. That means we go on catching flu over and over again, with little or no immunity from previous attacks unless they are recent.

If the virus is dangerous enough, you can be seriously ill or dead before your own white cells have had a chance to mobilise. And some viruses are immune to your own immune defences - like HIV - so that they kill slowly, even though the body is producing a strong reaction.

Vaccines against Bird Flu - do they work?

Vaccines are very effective so long as the virus causing a particular illness is stable, and we have enough time to scale up production - both of these things are true of polio for example. Immunity will then last a very long time.

However, new vaccines take time to develop, once scientists have identified a new strain of virus. it takes many months to scale up enough to treat the most vulnerable in the wealthiest nations, and years to generate enough for most people in the world, which is why governments have started stockpiling drugs that have some effect on flu illness - if taken early enough. The drugs are nothing like as powerful as antibiotics in bacterial infections, but they are all we have, and viruses can rapidly become resistant - as we are already seeing in treating early cases of bird flu in South East Asia. There are also problems in producing antiviral drugs fast enough. Some governments will not get the amount of drugs they have ordered until well into the middle of 2006.

Once a mutation is identified, a vaccine can be prepared, but as I say, making it in large enough doses to prevent a pandemic is likely to take many months, and may not arrive in time. And even if it did, the fact is that 3 billion people live in areas with low health budgets and poorly developed health care systems.

It would be impossible to vaccinate the whole world in time, because a Bird Flu pandemic could sweep around the entire globe in a few weeks or months.

However it may be that a new mutation could be similar enough to old flu viruses for existing vaccines to have some effect. We just do not know.

Many viruses mutate all the time

Picture of flu virus

Many viruses are unstable and change all the time. Every time a new person or animal is infected, there is a chance of another mutation. Viruses also combine in unpredictable ways if a cell is infected with more than one virus type. The cell becomes confused about which virus it is making, and elements of both viruses get muddled up to create a new hybrid.

Take the example of a farmer who gets human flu, and at the same time has caught a virus from one of his animals which is going to kill him. It could be that the animal virus can only pass between animals, or from an animal to a human - and it might not be very infectious, so the infection will probably die out when he dies. But inside the farmer's body it is possible that the virus might mutate into one which is as infectious as human flu, and as lethal as the animal virus.

And how could you tell this has happened?

This is exactly the kind of nightmare that is keeping scientists awake at night in different research laboratories around the world.

Take bird flu: we keep seeing small numbers of human beings get infected and die, and sometimes we see clusters of cases, especially in families, which could indicate that the virus is learning how to spread between people. Of course clusters can also occur where several family members have been exposed to the same sick animal, which makes these things even harder to monitor.

We saw a similar process happen with SARS - a highly infectious virus managed to jump from animals to humans, and was only contained with huge health control efforts. We were very fortunate that SARS did not spread to countries like Burundi in Africa, which would not have had the resources to trace contacts and impose strict isolation. If it had, we would still have a dangerous SARS epidemic in Africa today.

Viruses can be very unstable

Viruses causing common cold change shape every few weeks, making vaccination impossible. Flu viruses nornally change shape every year or so, which means that people have to be vaccinated each year.

HIV is highly unstable. It is possible to find up to 25,000 differently shaped versions of the virus inside a single person who is infected. That's why we are still trying to find a vaccine despite 45 million deaths, 85 million infections and an epidemic that is out of control in many parts of the world.

So what is the answer to Bird Flu?

Every effort is being made to stamp out the Bird Flu epidemic by killing chickens that are sick, or could be infected. Other health measures include keeping chickens away from living areas of those that keep them, in areas where Bird Flu has been detected; educating people about not eating sick birds; teaching people about the early symptoms of Bird Flu; encouraging them to seek medical help early; treating those with Bird Flu in isolation.

Control is now very difficult in domestic birds, because the bird flu infection is spreading widely amongst wild birds, many of which migrate over long distances. That is probably the explanation for October 2005 outbreaks in Turkey and Romania.

Viral Epidemics Will Remain a Serious Threat

While we hope that Bird Flu will be brought under control, and while a "worst case scenario" global pandemic remains unlikely, the threat from mutant viruses remains and constant vigilance is needed. We will continue to see headlines about new outbreaks of lethal viruses, whether Ebola Virus, new strains of SARS, HIV, Bird Flu and so on.

Fortunately most new lethal viruses kill the few they infect very quickly, before the virus has a chance to spread widely, and the new infections die out. Other new viruses often become less virulent and dangerous as they infect more people. The most dangerous are viruses which kill a minority of those they infect, are easily transmitted, and cause little signs in people who are infectious in the early stages.

Bird Flu information summarised from WHO

What is Avian Influenza? Avian influenza is an infectious disease of birds caused by type A strains of influenza virus. The disease was first found in Italy more than 100 years ago, but can occur worldwide.

All kinds of birds can catch avian influenza, though some species are more resistant than others. Infection causes many different symptoms in birds, ranging from mild illness to highly infectious and rapidly fatal disease resulting in severe epidemics. This more lethal can produce sudden illness and death in almost all cases.

How many kinds of Bird Flu are there? Fifteen variants of influenza virus are known to infect birds. Up until April 2005, all outbreaks of the highly pathogenic form were caused by influenza A viruses of subtypes H5 and H7.

Migratory waterfowl - mainly wild ducks - are the natural reservoir of avian influenza viruses, and these birds have some immunity to them. Domestic poultry, including chickens and turkeys, are particularly vulnerable to epidemics of rapidly fatal influenza.

Direct or indirect contact of domestic flocks with wild migratory waterfowl is a frequent cause of epidemics. Live bird markets have also played an important role in spread.

Mild strains can rapidly mutate into lethal ones as they spread throuhg poultry. During a 1983-1984 epidemic in the United States of America, the H5N2 virus initially caused few deaths, but within six months became highly dangerous, with death rates approaching 90%. Control required destruction of more than 19 million birds at a cost of nearly US$ 65 million.

During a 1999-2001 epidemic in Italy, the H7N1 virus was first mild in impact, but rapidly became highly dangerous. More than 13 million birds died or were destroyed.

Strict quarantine (isolation) of infected farms and destruction of infected or potentially exposed flocks are standard control measures aimed at preventing spread to other farms and across an entire country.

Apart from being highly infectious, avian influenza viruses are easily spead from farm to farm by contaminated equipment, vehicles, feed, cages, or clothing.

Highly dangerous Bird Flu viruses can survive for long periods in the environment, especially when temperatures are low. Strict hygiene and disinfection measures on farms can, however, help prevent this.

If you don't act fast at the beginning, and monitor very carefully for fresh outbreaks,, epidemics can last for years. For example, an epidemic of H5N2 avian influenza began in Mexico in 1992, as a mild virus, evolved to the highly fatal form, and was not controlled until 1995.

A constantly mutating virus: two results

All type A influenza viruses, including those that regularly cause seasonal epidemics of influenza in humans, are genetically unstable and well adapted to host defenses. Influenza viruses lack mechanisms for "proofreading" and repair of errors that occur during replication. As a result of these uncorrected errors, the genetic composition of the viruses changes as they replicate in humans and animals, and the existing strain is replaced with a new antigenic variant. These constant, permanent and usually small changes in the antigenic composition of influenza A viruses are known as antigenic "drift".

The tendency of influenza viruses to undergo frequent and permanent antigenic changes necessitates constant monitoring of the global influenza situation and annual adjustments in the composition of influenza vaccines. Both activities have been a cornerstone of the WHO Global Influenza Programme since it began work in 1947.

influenza A viruses, including subtypes from different species, can swap or "reassort" genetic materials and merge. This is, known as antigenic "shift", and the result is a novel subtype different from both parent viruses. As populations have no immunity to the new subtype, and as no existing vaccines can confer protection, antigenic shift has often resulted in highly lethal pandemics. For this to happen, the new subtype needs to have genes from human influenza viruses that make it highly infectious for a long period.

Conditions favourable for the emergence of antigenic shift have long been thought to involve humans living in close proximity to domestic poultry and pigs. Because pigs are susceptible to infection with both avian and mammalian viruses, including human strains, they can serve as a "mixing vessel" for scrambling of genetic material from human and avian viruses, resulting in new mutations.

Evidence is mounting that, for at least some of the 15 avian influenza virus subtypes circulating in bird populations, humans themselves can be such a"mixing vessel".

History of Human infection with avian influenza viruses

The first documented infection of humans with an avian influenza virus was in Hong Kong in 1997, when the H5N1 strain caused severe respiratory disease in 18 humans, of whom 6 died. This outbreak coincided with an epidemic of highly pathogenic avian influenza, caused by the same strain, in Hong Kong's poultry population.

Investigation showed that close contact with live infected poultry was the source of human infection - virus jumped directly from birds to humans. Limited transmission to health care workers occurred, but did not cause severe disease.

Rapid destruction - within three days - of Hong Kong's entire poultry population, estimated at around 1.5 million birds, reduced opportunities for further direct transmission to humans, and may have averted a pandemic.

That event alarmed public health authorities, as it was the first time that an avian influenza virus was transmitted directly to humans and caused severe illness with high death rates. Iin February 2003, an outbreak of H5N1 avian influenza in Hong Kong caused 2 cases and 1 death in members of a family who had recently travelled to southern China. Another child in the family died during that visit, but the cause of death is not known.

Two other avian influenza viruses havecaused illness in humans. An outbreak of highly pathogenic H7N7 avian influenza began in the Netherlands in February 2003, causing the death of a vet two months later, and mild illness in 83 other people. Mild cases of avian influenza H9N2 in children occurred in Hong Kong in 1999 (two cases) and in mid-December 2003 (one case). H9N2 is not highly pathogenic in birds.

The most recent cause for alarm occurred in January 2004, when laboratory tests confirmed the presence of H5N1 avian influenza virus in human cases of severe respiratory disease in the northern part of Viet Nam.

Why people are worried about H5N1

Of the 15 avian influenza virus subtypes, H5N1 mutates rapidly and is good at acquiring new genes from viruses infecting other animal species. It is known to cause severe disease in humans. Birds that survive infection excrete virus for at least 10 days, orally and in faeces, so further spread is a great risk at live poultry markets and by migratory birds.

The epidemic of highly pathogenic avian influenza caused by H5N1, which began in mid-December 2003 in the Republic of Korea and is now being seen in other Asian countries. H5N1 variants demonstrated a capacity to directly infect humans in 1997, and have done so again in Viet Nam in January 2004. The spread of infection in birds increases the opportunities for direct infection of humans, with growing risks of a new world-wide flu epidemic if viruses mix in humans.

Several measures can help minimize the global public health risks that could arise from large outbreaks of highly pathogenic H5N1 avian influenza in birds. First - urgent need to halt further spread of epidemics in poultry populations, and reduce opportunities for human exposure to the virus. Vaccination of persons at high risk of exposure to infected poultry, using existing vaccines effective against currently circulating human influenza strains, can reduce risk of co-infection of humans with avian and influenza strains, and risk that genes will be exchanged. Workers involved in the culling of poultry flocks must be protected, by proper clothing and equipment, against infection. These workers should also receive antiviral drugs as a prevention measure.

When cases of avian influenza are seen in humans, information must be made available quickly. Thorough investigation of each case is also essential.

Clinical course and treatment

In the 1997 Hong Kong outbreak, patients developed symptoms of fever, sore throat, cough and, in several fatal cases, severe respiratory distress secondary to viral pneumonia. Previously healthy adults and children, and some with chronic medical conditions, were affected.

Tests for diagnosing all influenza strains of animals and humans are rapid and reliable. Many laboratories havehigh-security facilities and reagents for performing these tests as well as experience. Rapid bedside tests for the diagnosis of human influenza are also available, but do not tell us if the virus is spreading between humans.

Antiviral drugs, some of which can be used for both treatment and prevention, have some effect against influenza A virus strains. Some of these drugs are expensive and supplies are limited.

Experience in the production of influenza vaccines is considerable. However, at least four months would be needed to produce a new vaccine, in significant quantities, capable of conferring protection against a new virus subtype.

For more see http://www.who.org

< Prev		Next >