Manila -- Influenza pandemics are recurring and unpredictable calamities. WHO and influenza experts worldwide are concerned that the recent appearance and widespread distribution of an avian influenza virus, Influenza A/H5N1, has the potential to ignite the next pandemic.

Give the current threat, WHO has urged all countries to develop or update their influenza pandemic preparedness plans (see information on web pages below) for responding to the widespread socioeconomic disruptions that would result from having large numbers of people unwell or dying.


Pandemic preparedness

Central to preparedness planning is an estimate of how deadly the next pandemic is likely to be. Experts´ answers to this fundamental question have ranged from 2 million to over 50 million. All these answers are scientifically grounded. The reasons for the wide range of estimates are manyfold.

Some estimates are based on extrapolations from past pandemics, but significant details of these events are disputed, including the true numbers of deaths that resulted. The most precise predictions are based on the pandemic in 1968, but even in this case estimates vary from one million to four million deaths. Similarly, the number of deaths from the Spanish flu pandemic of 1918 is posited by different investigators to range from 20 million to well over 50 million.

Extrapolations are problematic because the world in 2004 is a different place from 1918. The impact of greatly improved nutrition and health care needs to be weighed against the impact the increase in international travel would have in terms of global spread.

The specific characteristics of a future pandemic virus cannot be predicted. It may affect between 20-50% of the total population. It is also unknown how pathogenic a novel virus would be, and which age groups will be affected.

The level of preparedness will also influence the final death toll. Even moderate pandemics can inflict a considerable burden on the unprepared and disadvantaged. Planning to maintain health care systems will be especially crucial. Good health care will play a central role in reducing the impact, yet the pandemic itself may disrupt the supply of essential medicines and health care workers may fall ill.

Because of these factors, confidently narrowing the range of estimates cannot be done until the pandemic emerges. Therefore, response plans need to be both strong and flexible.

Even in the best case scenarios of the next pandemic, 2 to 7 million people would die and tens of millions would require medical attention. If the next pandemic virus is a very virulent strain, deaths could be dramatically higher.

The global spread of a pandemic cannot be stopped but preparedness will reduce its impact. WHO will continue to urge preparedness and assist Member States in these activities. In the next few weeks, WHO will be publishing a national assessment tool to evaluate and focus national preparedness efforts. WHO will also be providing guidance on stockpiling antivirals and vaccines. Next week, WHO will be convening an expert meeting on preparedness planning. WHO is also working to advance development of pandemic virus vaccines, and to expedite research efforts to understand the mechanisms of emergence and spread of influenza pandemics.

It is of central importance that Member States take the necessary steps to develop their own preparedness plans. Some have already developed structures and processes to counter the threat of a pandemic, but some plans are far from complete and many Member States have yet to begin.

WHO believes the appearance of H5N1, which is now widely entrenched in Asia, signals that the world has moved closer to the next pandemic. While it is impossible to accurately forecast the magnitude of the next pandemic, we do know that much of the world is unprepared for a pandemic of any size.

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For more information, please contact: Mr Peter Cordingley at (63 2) 528 9991 to 93, mobile (63 917) 844 3688; email: PIO_Unit@wpro.who.int.