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Many people claim to have the flu each year.  Most of the time they are misdiagnosing themselves, confusing a severe cough/cold with real flu.

Real flu is vastly more severe than a cough and cold.  People regularly die from the flu.  They don't die from coughs or colds.

Here's scary information about a new 'super flu' that threatens to overwhelm the world and its health care resources.

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All about H5N1 Avian or Bird Flu

Is this an upcoming pandemic threatening us all?

Flu virus under an electron microscope, magnified 100,000 times

Influenza is the name given to a family of viruses with generally similar properties.

These viruses mutate and it seems each year has a slightly different strain of virus traveling around the world.

In the past there have been occasional pandemics of influenza, the most notable of which was the Spanish Flu in 1918-19.

Some people believe there is a grave danger of a new pandemic in the near future.  Here's why.

Part 1 of a 3 part series - part 2 discusses strategies to minimize your risk of infection and what to do if you should come down with Bird or Swine Flu.  Part 3 will discuss the social problems that may occur during any type of Flu pandemic and offers some suggestions about how to survive in a potentially hostile, foodless and lawless world.



Influenza is commonly confused with the common cold.  Although both are viral in origin, and both may share some symptoms (eg a cough), real influenza is a much more severe affliction that people regularly die from.

Different types of flu vary in terms of how easily they can be passed from one infected person to another person, and in terms of how severe an illness they cause.  It is happily rare to find a strain of flu that is both highly infectious and also very lethal.

But on occasion, this can and does occur.  There is a danger that the world may be about to confront another one of these 'super-flu' outbreaks, based on what is currently termed avian flu or bird flu, and scientifically described as the H5N1 flu.

Important Disclaimer

I have no medical qualifications and this article is not intended as medical advice.  Although I've had physicians check the article for gross errors and inaccuracies, they too would not want you solely relying on this article, and we all urge you to check with your personal health care provider and prepare a strategy best suited for your situation.

Lessons from the Past - the 1918-19 Spanish Flu Pandemic

Most people remember reading about the Black Death - the plague - in the Middle Ages.  This was a horrifying pandemic (see below for definitions), all across Europe, with many people dying.  But, at the same time, we relegate our knowledge of that to a 'could never happen to us in today's society' category.  Probably this is true.

Surprisingly, though, there's a much more relevant example of a pandemic, and one with clear lessons for us today.  This example is less appreciated - the outbreak of influenza in 1918 that grew to become the worst pandemic in world history.  More people died in a single year than died in the four years of the plague between 1347-1351; and twice as many people died in six months than died in all of the four years of World War 1.

Exact numbers for this pandemic are hard to establish, and different sources offer different numbers, but in the same general range.  Estimates suggest that between 20% and 50% of the entire world's population was infected, and as many as 50 million people died.  Surprisingly, people in the 15-40 age group - normally the segment of the population most resistant to infections - were seemingly the most at risk.

The death rate in the US was approximately 2.5%, compared to a 'normal' year's flu which was about 0.1%.  In other countries the death rate ranged up as high as 5%.

The flu would attack quickly, with people transitioning from apparently healthy to dead in less than a day.  25% of the US population was infected, even President Woodrow Wilson caught the flu.

Initially, governments were slow to acknowledge this outbreak and the danger it posed, and preferred to refer to the pandemic as 'only the flu' so as to prevent panic.  But as the world fell into the grip of what became termed the 'Spanish Flu', social disruptions became increasingly extreme.  Restrictions were placed on public gatherings (including funerals and even store sales) and on travel.  In San Francisco and San Diego it became compulsory to wear gauze masks in public, and one town made shaking hands illegal.

Desperate shortages of health care professionals existed, and similar shortages affected other service industries - in some cities, there were not enough phone operators to allow for normal phone service.  There were also shortages of coffins, morticians and grave-diggers, such that mass graves were dug by steam shovel and dead bodies buried en masse.

To put the impact of this flu outbreak in another context, 25 million people have died of AIDS in the first 25 years of this disease.  In comparison, 25 million people died of flu (in a world with a much smaller population) in 25 weeks.

The Spanish Flu outbreak occurred 87 years ago.  What is the relevance of Spanish Flu then to Bird Flu now?

Not only does the Spanish Flu outbreak give us a taste for what could occur with a new outbreak of a virulent strain of influenza, but recent research now suggests that the Spanish Flu virus was initially a bird flu virus of type H1N1 which mutated and became capable of attacking and being transmitted between humans - exactly as is feared for Bird Flu.

The Potential Dangers with Avian/Bird Flu

An unprecedented epizootic avian influenza A (H5N1) virus that is highly pathogenic has crossed the species barrier in Asia to cause many human fatalities and poses an increasing pandemic threat.

The reality of the dangers of Avian Flu is changing daily - and getting worse with each passing day.  These words, above, open a 29 Sept 2005 scholarly article in the New England Journal of Medicine, and represent perhaps the most recent version of the truth and also one of the most apocalyptic.

At present the H5N1 strain of influenza, commonly called Avian Flu or Bird Flu has been thought to be primarily a threat to bird populations.

It was first uncovered in poultry in Hong Kong back in 1997, but is not restricted only to poultry.  It seems to freely attack most types of birds, including long-range migratory birds.  Its presence in wild migratory birds makes it easily passed around the world, and indeed it has been moving out from its original base in Hong Kong and now is in much of Asia and moving into Eastern Europe (primarily in Russia, almost to the Ural Mountains).

The impact of this disease on bird populations is unfortunate, but in and of itself, is little reason to provoke alarm in humans.  But there are some reasons to be concerned.

Firstly, the disease seems able to be weakly transmitted from birds to people.  Some - but not many - people who are in regular close contact with poultry have been affected by the disease as well, and apparently some visitors to a zoo in Indonesia were also infected, although it is unclear if this infection was from birds or from perhaps another person.

Secondly, when a person is infected by H5N1 flu, the mortality rate - chance of them dying - is extremely high.  It is hard to be specific at this early stage, but estimates of mortality rates are ranging up above 50% (as of 5 August 2005, there were 112 cases and 57 deaths, outside of China.  Total deaths have now (late Sept) increased to 65, but a matching number of total cases is not available.)  In contrast, 'only' 2.5% - 5% of people infected with Spanish Flu died.

Remember this number.  H5N1 is currently proving to be at least ten times more lethal than Spanish Flu.

On the other hand, these early statistics, like first returns from an election, can be misleading.  It is quite possible that not all cases of H5N1 infection (where the person survives) has been accurately tracked, and of course, the infections to date have been in third world countries with generally poor standards of nutrition and healthcare.  Actual mortality rates may be much lower than presently indicated.

Thirdly, although at present the disease has not yet been proven to be transmittable from one person to another, this may change.  There are a couple of ways this could occur - a random mutation in the virus could do this, or the H5N1 virus could be passed to a person infected with a 'regular' (ie person to person type) flu virus; the two flu viruses could exchange genes, causing a new strain of the H5N1 to become transmittable between people.

If this occurs, a devastating global pandemic becomes possible.

How Likely is it the Virus will Evolve to Human to Human Infection

Bird Flu was first discovered in 1997.  Why are we worrying about it now, eight years later?  Surely, if there was a clear and present danger, it would have already manifested itself?

Some people have asked these questions as a way of suggesting concerns about Bird Flu are being overstated.  But the Bird Flu problem is contained within these two questioning statements.  Firstly, Bird Flu has shown itself to be difficult to contain and/or eliminate.  Bird Flu has become more widespread with the passing of time; it is getting more widely distributed and infecting more and more bird populations, in more and more countries, every week.  The very small risk factor associated with Bird Flu in 1997 has been steadily growing ever since.

Secondly, the chances of the H5N1 Bird/Avian Flu virus evolving into something dangerous to humans increases based on two things - the prevalence of Bird Flu, and the length of time it has been in existence.  The more time the virus has, the greater the chance that a random change in its makeup will make it more dangerous to humans.

Accepting then that Bird Flu's eight year life to date is not a reason for complacency but rather a reason for concern, we should consider two issues.  Firstly, will such an evolution occur, and secondly, how infectious will the resulting virus be?

The Virus is already evolving

The answer to the first question might be unexpected.  There are already (as of September 05) between four and six known cases of human to human transmission of the H5N1 virus.  See, for example, this report.

And this article contains alarming data that suggests human to human transmission is already occurring in Indonesia.  This article, two days later, adds to the concern.

Still not convinced?  This page from the CDC website and headed 'Outbreak Notice:  Human Avian influenza, Asia' will probably change on a regular basis, but on 27 Sep 2005 included the text 'A few cases of person-to-person spread of H5N1 viruses may have occurred.'

Note the first of these articles refers to the disease moving to a 'phase five'.  This is one step short of phase six which is a fully fledged world pandemic.  The WHO, (World Health Organization, and author of these six levels of alert (detailed below)), is currently treating Avian Flu only as a phase three alert.

Some people have said there is no direct evidence the virus is about to mutate into a human to human transmittable form.  That claim may already be negated by the information above, but even if still true, the statement is meaningless - it is a bit like saying 'there is no direct evidence the next time you roll the dice it will come up with a six'.

The likelihood of mutation increases over time, and as more and more people are exposed to infected birds.  The virus might never mutate into a robust human to human transmittable form, and most mutations lead to a weaker rather than stronger organism.  But, on the other hand, it might.  And, in particular, if the H5N1 virus invades a person already carrying a human to human version of the flu, the chance of the two viruses exchanging DNA and acquiring attributes of each other increases.

How infectious would such a mutated virus be?  Nobody yet knows.  Maybe it will be a very weak virus that is hard to pass on to other people.  Or maybe it will be a super infectious virus, long lived, hard to destroy, and dangerous in very small quantities.

There are many unknowns here.  But the extraordinary danger that accompanies the risk of realistic scenarios is surely more than sufficient to motivate us and our governments to do all we can to stop this from happening.

The Government (or Science) Will Save Us?

I spoke about Bird Flu with my general practitioner, and he agreed about the grave dangers posed by Bird Flu.  But he concluded by saying he believed/hoped that technology would triumph, and by the time the virus became a major problem, there'd be a vaccination or cure for it.

How realistic is this hope?  Alas, not very, although a lot depends on the timeline of when (if) the virus starts actively passing from person to person, and if a vaccine is developed and distributed prior to this occurring.

Flu Vaccine

As of the time of writing (Sept 05) there is no vaccine effective against the H5N1 strain of Avian Flu.  There are a couple of vaccines under development, but it is unclear if they will pass all testing, and - if/when they do - how long it would take for them to enter mass production, and how much longer it would then take for a realistic number of doses to be made available to the general population (approximately 6.5 billion).

The vaccines under development are expected to enter trials variously later this year or next year.

Probably it will be more than six months after a suitable virus has been developed before limited quantities of vaccine become available, and substantially longer than that before sufficient (how much is sufficient when we're talking about a world-wide pandemic?) quantities are made.

To quote from a page on the WHO website (link no longer active)

Current global manufacturing capacity (estimated at 300 million doses of regular trivalent influenza vaccine per year) is inadequate to meet the expected global needs during a pandemic and cannot be rapidly augmented.

Flu Drugs

There are two main families of drugs used to fight an infection once a person has been diagnosed with H5N1 flu.  The first of these types of drugs - M2 inhibitors such as amantadine and rimantadine - have been widely in use for some years.  Unfortunately, indiscriminate and uncontrolled dosing of poultry with these drugs in China means, as of the time of writing (Sept 05), most strains of the H5N1 virus have developed resistance to these drugs.

The other family of drugs - neuraminidase inhibitors such as zanamivir and oseltamivir (Tamiflu) - are more expensive and have not been so widely used to date.  While it seems the virus has not yet developed any effective resistance to these drugs, with the passing of time and their continued use, the second family of medicines must be considered vulnerable to the virus developing resistance too.

Unfortunately, Tamiflu is in short supply, and most countries and their public health authorities have insufficient stocks in case of a pandemic.

Update 2009 :  Tamiflu is nowadays much less effective, due to the flu virus mutating in response to Tamiflu to become resistant.

Preparing for an Outbreak

If an outbreak of H5N1 Avian Flu were to occur, the best response would be to urgently give infected people courses of the anti-viral Tamiflu drug, and possibly also to give extra courses of Tamiflu to people in close contact with the infected person.

Each course of Tamiflu for one person comprises ten 75mg tablets.  Taking Tamiflu as a preventative measure rather than as a cure can require even larger numbers of tablets, depending on the length of time the protection is desired (you are only protected against the flu while actively taking the tablets - there is no lasting effect).

But if an outbreak were to occur and spread with anything like the speed of the Spanish Flu in 1918 (25 million dying within the first half year) the world would need access to huge amounts of Tamiflu.  We'd be reliant on public health authorities having stockpiles of the drug.

Although governments are slowly recognizing the danger and ordering supplies of Tamiflu, no government is ordering sufficient amounts for their entire population, and very few are ordering enough for even one third the population.  The UK has stockpiled 15 million courses, enough for one quarter of their population.  France also has enough for one quarter of its population.  Australia has 4 million doses, sufficient for 20%.  But the US?  We have only enough Tamiflu stockpiled for 1% of our population.

Even those countries that are ordering large quantities have priority lists of who will get access to them.  If you're not a politician, health care worker, or other key services employee, your chances of getting access to these stockpiles is very limited.

Based on current and projected near-term future order fulfillments, a widespread outbreak of Bird Flu could very quickly lead to all supplies of Tamiflu being exhausted.  Indeed, my local pharmacy on 28 Sept was out of stock, although they expect more in soon.

All of the above assumes the virus doesn't gain resistance to Tamiflu.  And this may already be occurring, as this article, dated back in May, suggests.  (Update 2009 - yes, Tamiflu's effectiveness is now massively reduced, and there's no new drug to replace Tamiflu).

Preventing Spread of Infection among People

The SARS danger was circumvented largely by effective controls on the movement of potentially infected individuals.

But if Bird Flu is to be transmitted both by people and by animals (obviously birds, and potentially cats and possibly pigs, too) then while we can realistically limit the movement of people, we almost certainly can't prevent the movement of wild birds.

Preventing Spread of Infection among Birds

Bird populations with the remotest likelihood of infected members need to be completely eradicated.  Some nations have been willing to do this.  Others have been less willing to suffer the economic damage they'd be inflicting on themselves.

Unfortunately, many of the South East Asian nations with Bird Flu infections are poor countries with low standards of health care, low standards of education, and high levels of corruption.  The temptation for officials to accept bribes and to allow bird flocks to remain unharmed must be great and at times overwhelming.

And while these nations might seem impossibly far away and removed from our way of life here, the reality is that many of them are no more than one or two flights away.  A person can be infected in South East Asia, and less than 24 hours later, he can be walking the streets and riding the subways in New York, coughing into the air around him, and spreading the infection.  One of those people riding alongside him in the subway can then fly to somewhere else, and so the chain of infection rapidly spreads like wildfire.

While this article primarily considers the implications of Bird Flu becoming a risk to humans, the economic damage that 'simple' Bird Flu can cause is also major.  Poultry is a major meat source in this and many other countries, and if there became a need for major culling of commercial poultry farms, not only would there be a direct cost to the affected farmers, but the resulting shortage of poultry would raise prices of all meat and poultry related products.

Controlling an outbreak in birds is proving to be difficult (this strain of Bird Flu has been around for eight years already).  Indeed, the current Bird Flu problem (in birds) is getting worse, not better.  Since mid-December 2003, a growing number of Asian countries have reported outbreaks of highly pathogenic avian influenza in chickens and ducks. Infections in several species of wild birds and in pigs have also been reported.

This following quote comes directly from the WHO website (link no longer present)

The rapid spread of highly pathogenic avian influenza, with outbreaks occurring at the same time in several countries, is historically unprecedented and of great concern for human health as well as for agriculture.

Is the Danger of H5N1 Flu being Deliberately Understated or Ignored?

It is probably not in the general interest of public order and contentment to unduly alarm or panic people over something that might never occur, and it seems likely that governments are seizing on this rationale as a reason to avoid dramatic public discussion of this problem.

Furthermore, an outbreak of a virulent strain of human H5N1 would be so apocalyptic and exceed anything in any of our memories or comprehension, so there is an automatic instinctive unwillingness to believe or accept the grim reality of what would occur, coupled with a desperate desire to hope that such terrible things may never come to pass.

But wishing something were not true does not change it, any more than an ostrich with its head in the sand becomes truly invisible.  The inexorable spread of an infectious disease makes no allowance for the social destruction it might be causing.

Modern society, rather than making a pandemic less likely, has all the factors to make such an occurrence more likely :  crowded living, working, and commuting conditions in many cities encourage and facilitate the spread of the disease, and large numbers of people traveling all around the world every day ensure the disease can spread not only within each minor community cluster, but between clusters and between countries, too.

Our society has a curious duality about acceptance of risk.  Some things with high risks we complacently accept without a second thought.  Smoking cigarettes, driving a car (drunk or sober!), unprotected sex with strangers; many things with high risk of serious consequence are accepted without any qualms.  But other situations with vastly lower risks attached - for example, living in a house with lead based paints or asbestos in the ceiling, or flying in planes - are considered very risky and surrounded with many controls and restrictions.

Our perception and acceptance of risk is irrational; but the threat posed by a Bird Flu pandemic demands a rational analysis and response.

Hurricane Katrina gives a good example of something that was considered to be so unlikely as to be not worth giving full attention to.  The result was $200+ billion dollars worth of rebuilding, hundreds of people dead, and hundreds of thousands more with lives transformed to misery.

A human to human infectious H5N1 virus is not a certainty.  But it is a possibility, and the chances of it occurring are probably similar to or greater than the chance of another Katrina hitting New Orleans.  The devastation caused by a human Avian Flu virus, not just in one small area, but to the entire country and entire world, is unthinkably larger than any natural disaster, whether measured in lives lost, the dollar cost of the pandemic and recovery from it, or any other parameter.

For the sake of ourselves and our families, we must consider this risk seriously and respond accordingly.

While some publicity is supporting this view, there is also a confusing and contradictory counter-current of 'relax, don't worry' type stories being published.

Here's a curious article which seeks to reassure us.  But unfortunately it contains some factual errors and some significant omissions.

For example, Bird Flu isn't restricted only to poultry - populations of migratory birds have also been infected, and are rapidly spreading the disease away from its initial location (Hong Kong).

And this quote 'Numerous health professionals are monitoring influenza; and, training, surveillance and education efforts continue. Plans for dealing with an influenza emergency have been developed and are continually updated so that the best control efforts available could be implemented should the need arise' sounds very reassuring, but is not backed up with the specifics of who these health professionals are, or what their plans are.  Anyone who relied on the government to save them from Hurricane Katrina will probably find these words less than reassuring.

Furthermore,  the elapsed time between the onset of an outbreak and a fully fledged pandemic may be very short, giving little or no time for public health officials to adequately respond, be they prepared or not.

While populist articles seem to often downplay the risk, medical journals tell a different story.  Indeed, Dr Julie Gerberding, head of the CDC - the Centers for Disease Control and Prevention; the US organization that would presumably be a first responder and coordinator of a flu crisis in the US, was quoted as saying (link broken) on 21 Feb 2005

Bird flu is the single biggest threat to the world right now and health officials may not yet have the tools they need to fight it.

In a report to the American Association for the Advancement of Science, she added 'this is a very ominous situation for the globe' calling it the 'most important threat we are facing right now.'

Here's another article, quoting from Northern Ireland's Department of Agriculture and Rural Development, claiming the risk of dangerous avian influenza reaching Western Europe is low.  This claim would seem to be largely contradicted by the facts they admit themselves - avian flu has already reached Russia.

But this article, linked from the same page, refers to other western nations as being fearful of the spread of the flu, and closes with a chilling quote from the Secretary General of the European Public Health Alliance, which represents 115 European health groups.  She says :

Millions and millions would die, and a pandemic would change society as we know it.  And no-one seems prepared.

On the other hand, the article also quotes a WHO spokesman as predicting that between two and seven million people could die, world-wide, if a pandemic (which he describes as 'inevitable'!) should break out.

This number seems comically (or is that, tragically?) low.  Somewhere up to 100 million people died from Spanish flu, a virus that killed 2.5% - 5% of the people it infected, in a world with only 1.8 billion people.  Today we have a world with 6.5 billion people and a virus that kills half of the people it infects.

What is the US Government Doing?

Here is a fascinating transcript (link no longer works) of a recent interview between Bill Moyers and Dr Anthony Fauci, director of the Institute for Allergy and Infectious Diseases at the National Institutes of Health on the PBS Wideangle show.

Some reassurance may perhaps be gleaned from this part of the interview :

BILL MOYERS: Ready. You know, we were not prepared for 9/11. We were not prepared for the ravages of Katrina. What makes you think we're going to prepare for this?

DR. ANTHONY FAUCI: Because we're on our way to doing that. There's a commitment that certainly the administration -- the President is committed to getting us prepared for a pandemic flu.

He's following it very carefully.

Secretary Leavitt of the Department of Health and Human Services, [it] is of highest priority for him in his department.

So this is something that at the very highest levels of our government from the White House to the Departments to the Congress are very concerned about this.

Unfortunately, Dr Fauci's comments seem contradicted by Senator Frist's comments, below.


There have been previous flu pandemic scares that have come to nothing.  It is possible that the potential danger of Bird Flu too will prove to be overstated - and let's all fervently hope this proves to be the situation.

But, wishful thinking to one side, the grim reality at present is that the persistence, growth and spread of Bird Flu virus in bird populations steadily increases the possibility that the virus not only may but can and will evolve into a form more compatible with human to human transmission.

If this happens, and if the virus remains as lethal to humans as it currently appears to be, the result could be horrifying.  Bird Flu is ten to twenty times more deadly to humans than was Spanish Flu in 1918-1919.  Without adequate prevention and controls, as much as 10% of the entire world's population - rich and poor, west and east - could die from a Bird Flu pandemic.  It is probable that such an event would destroy much of our present civilization and society for an extended period of time.

At present there is little reassuring evidence that adequate prevention and control measures are in place.  Forget about worrying if an asteroid might hit the planet, don't worry about global warming, and ignore the energy crisis.  Although a Bird Flu pandemic is far from certain, if it were to occur, the immediate disaster to all of us would eclipse any of these other future problems.

Accordingly, everyone's highest priority must be to resolve the clearest and most present danger to life as we know it - Bird Flu.

We'll give the last word to surgeon and politician Bill Frist, who starts off a must read piece in the Washington Times on 29 Sept by criticizing his own government's administration by saying :

The avian flu virus is a pathogen invisible to the human eye which poses an immense potential threat to American civilization. In the past several months, it has become clear to me that we remain dangerously unprepared to defend ourselves against it....

Read more in Parts 2 and 3

In Part 2 we discuss strategies to minimize your risk of infection and what to do if you should come down with Bird or Swine Flu.  Part 3 will discuss the social problems that may occur during any type of Flu pandemic and offers some suggestions about how to survive in a potentially hostile, foodless and lawless world.

Reference Resources

This subject is rapidly evolving and the information in these two articles may quickly become out of date.  Fortunately, there are a number of websites that are dedicated to distributing the latest information about Avian Flu.

Centers for Disease Control and Prevention section on Avian Flu

National Foundation for Infectious Diseases Information about Influenza (link no longer works)

World Health Organization section on Avian Influenza


The following terms are often used in discussions of influenza and other diseases, and so these definitions may be helpful.

Communicable (disease)

A communicable disease is one which is both contagious and also which can be passed on indirectly (as by a fomite or vector).

Contagious (disease)

A disease is said to be contagious if it can be passed on by contact between an infected person, or a discharge from such a person, and an uninfected person.


A word that sounds like epidemic but which means something quite different.  An endemic thing is something that is generally restricted to a specific location.


A thing which affects an unusually large number of people in a region at the same time.


A fomite is a physical object that acts as an intermediary in the transmission of a disease from one person to another.  For example, if you cough onto a door handle which another person then touches and then puts his contaminated hand in his mouth, the door handle has acted as a fomite.  cf vector.


Influenza viruses are categorized by the subtype of two surface antigens on the virus, a Hemagglutinin type and a Neuraminidase type.  There are at least 16 different H antigens and nine N types (with types N1 and N2 being capable of causing infections in people).


This refers to a disease having a broader capacity to be passed on to an uninfected person than a contagious disease.  All contagious diseases are infectious, but not all infectious diseases are contagious.  An infectious disease is one caused by the introduction of organisms (eg bacteria or viruses) into one's body which then grow and multiply there.


Can be thought of as a more severe epidemic in terms of the percentage people affected, and extending over a broader region.


A vector is an animate organism that transfers disease from one person to another person.  For example, mosquitos are the vector for malaria.  cf fomite.

The Six Phases of a Pandemic

The World Health Organization (WHO) has developed a global influenza preparedness plan, which defines the stages of a pandemic, outlines WHO’s role and makes recommendations for national measures before and during a pandemic. The phases are :

Interpandemic period

Phase 1 : No new influenza virus subtypes have been detected in humans. An influenza virus subtype that has caused human infection may be present in animals. If present in animals, the risk of human infection or disease is considered to be low.

Phase 2 : No new influenza virus subtypes have been detected in humans. However, a circulating animal influenza virus subtype poses a substantial risk of human disease.

Pandemic alert period

Phase 3 : Human infection(s) with a new subtype, but no human-to-human spread, or at most rare instances of spread to a close contact.

Phase 4 : Small cluster(s) with limited human-to-human transmission but spread is highly localized, suggesting that the virus is not well adapted to humans.

Phase 5 : Larger cluster(s) but human-to-human spread still localized, suggesting that the virus is becoming increasingly better adapted to humans, but may not yet be fully transmissible (substantial pandemic risk).

Pandemic period

Phase 6 : Pandemic: increased and sustained transmission in general population. 

Important Disclaimer

I have no medical qualifications and this article is not intended as medical advice.  Although I've had physicians check the article for gross errors and inaccuracies, they too would not want you solely relying on this article, and we all urge you to check with your personal health care provider and prepare a strategy best suited for your situation.

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Originally published 30 Sep 2005, last update 20 Jul 2020

You may freely reproduce or distribute this article for noncommercial purposes as long as you give credit to me as original writer.



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