Mortality⁴

Central to preparedness planning is estimating the mortality rate of the next pandemic. Experts' answers to this fundamental question have ranged from 2 million to more than 50 million. All of these predictions are scientifically grounded. The reasons for the wide range of estimates are numerous.

Some estimates are based on extrapolations from past pandemics but significant details of these events are disputed, such as the true numbers of resulting deaths. The most precise predictions are based on the pandemic in 1968, but even in this case, estimates vary from 1 million to 4 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 of today is a different place from the world of 1918. The impact of greatly improved nutrition and healthcare needs to be weighed against the contribution that the increase in international travel would have on global spread. The specific characteristics of a future pandemic virus cannot be predicted. It may affect 20% to 50% of the total population. It is also unknown how pathogenic a novel virus would be.

Even in the best-case scenarios of the next pandemic, 2 to 7 million people could die and tens of millions could require medical attention worldwide.

Reference:
4.	World Health Organization. Estimating the impact of the next influenza pandemic: enhancing preparedness. December 8, 2004. Available at: http://www.who.int/csr/disease/influenza/preparedness2004_12_08/en/. Accessed April 13, 2006.