If you're just beginning to study the pandemic risk posed by the H5N1 avian influenza (bird flu), the World Health Organization has boiled down the key information in "Ten things you need to know about pandemic influenza." I've reproduced the list below, edited and shortened a bit for faster reading.
If nothing else, simply take 30 seconds to read the bolded subheadings below. That's the highest level "situation summary" you're going to find.
(In December, I posted a fuller "Situation Summary" based on these "Ten things" and five other publications.)
1. Pandemic influenza is different from avian influenza.
Avian influenza refers to a large group of different influenza viruses that primarily affect birds. On rare occasions, these bird viruses adapt the ability to infect humans. At that point, it's no longer a bird virus, but a human influenza virus.
An influenza pandemic happens when a new virus subtype emerges which has not previously circulated in humans (therefore people generally have no immunity to it). The avian virus H5N1 is such a case. It might ultimately adapt into a strain that is contagious among humans. But right now, it's still a bird virus, not a human virus.
2. Influenza pandemics are recurring events.
Influenza pandemics are somewhat rare but they do happen from time to time. Three pandemics occurred in the last century: the great "Spanish influenza" in 1918 and lesser pandemics in 1957 and 1968.
3. The world may be on the brink of another pandemic.
Health experts have been monitoring the H5N1 strain - a new and extremely severe influenza virus – for almost eight years. The H5N1 strain first infected humans in Hong Kong in 1997, causing 18 cases, including six deaths. Since mid-2003, this virus has caused the largest and most severe outbreaks in poultry ever seen. Since December 2003, human infections have again been occurring - first in Asian countries (Cambodia, Indonesia, Thailand, Viet Nam, and China) and more recently in Turkey and Iraq.
As of February 6, 2006, there have been 165 documented human cases, including 88 deaths.
Fortunately, the H5N1 virus does not jump easily from birds to humans or spread readily and sustainably among humans. Should H5N1 evolve to a form as contagious as normal influenza, a pandemic could begin.
4. All countries will be affected by any pandemic.
Once a fully contagious virus emerges, its global spread is considered inevitable. Countries might, through measures such as border closures and travel restrictions, delay arrival of the virus, but cannot stop it.
5. Widespread illness will occur.
Because most people will have no immunity to the pandemic virus, infection and illness rates are expected to be higher than during seasonal epidemics of normal influenza. It is estimated that a substantial percentage of the world’s population will require some form of medical care. Few countries have the staff, facilities, equipment, and hospital beds needed to cope with large numbers of people who suddenly fall ill.
6. Medical supplies will be inadequate.
Supplies of vaccines and antiviral drugs – the two most important medical interventions for reducing illness and deaths during a pandemic – will be inadequate in all countries at the start of a pandemic and for many months thereafter. Inadequate supplies of vaccines are of particular concern, as vaccines are considered the first line of defense for protecting populations. On present trends, many developing countries will have no access to vaccines throughout the duration of a pandemic.
7. Large numbers of deaths will occur.
Historically, the number of deaths during a pandemic has varied greatly. Because of variable factors, accurate predictions of mortality cannot be made before the pandemic virus emerges and begins to spread. All estimates are purely speculative.
For planning purposes, WHO has used a relatively conservative estimate – from 2 million to 7.4 million deaths – based on the comparatively mild 1957 pandemic. A more virulent virus (closer to the one seen in 1918) would cause a much higher number of deaths, according to estimates.
8. Economic and social disruption will be great.
High rates of illness and worker absenteeism are expected during a flu pandemic, and these will contribute to social and economic disruption. Such disruptions could be temporary, but may be amplified in today’s closely interrelated and interdependent systems of trade and commerce. Social disruption may be greatest when rates of absenteeism impair essential services, such as power, transportation, and communications.
Past pandemics have spread globally in two and sometimes three waves. Not all parts of the world or of a single country are expected to be severely affected at the same time.
9. Every country must be prepared.
WHO has issued a series of recommended strategic actions for responding to the influenza pandemic threat. The actions are designed to provide different layers of defense that reflect the complexity of the evolving situation.
10. WHO will alert the world when the pandemic threat increases.
WHO works closely with ministries of health and various public health organizations to support countries' surveillance of circulating influenza strains. A sensitive surveillance system that can detect emerging influenza strains is essential for the rapid detection of a pandemic virus.
To facilitate pandemic preparedness planning, six distinct alert phases have been defined. Each phase defines roles for governments, industry, and WHO. We are presently in alert phase 3: a virus new to humans is causing infections, but does not spread easily from one person to another.