Pandemic flu would kill 62 million people around the world, most of them in poorer countries, a new estimate suggests.

The figures assume that a new pandemic would follow the same pattern as the 1918 Spanish flu, which killed at least 20 million people at a time when the world’s population was much smaller.

Researchers from the Harvard School of Public Health and the University of Queensland analysed data from 27 countries to estimate just how deadly the 1918 flu was, and to estimate — based on today’s population — how many people would die, and where, if it were repeated. Their findings are published in The Lancet.

A new pandemic might not mimic precisely the course of the 1918 flu, but it is the best model there is.

A team led by Professor Christopher Murray, of Harvard, re-examined historical data and found that the 1918 pandemic hit the poor disproportionately hard. They say that if the same pandemic were to occur today, about 96 per cent of deaths would be in developing countries.

The published data, however, always has assumed that deaths were evenly spread, so that richer countries, with 20 per cent of the world population at the time, were assumed to have suffered 20 per cent of the deaths. “But when you look at the data, that number shrinks to about 3 or 4 per cent,” said Professor Murray.

“This is particularly alarming when you consider that all the policy protection is aimed at the high-income world. Few strategies are being thought through that are primarily targeting poor countries.”

The gaps between rich and poor countries in 1918-19 are striking. In Denmark, 0.2 per cent of the population died; in England, 0.34 per cent; and in the US, 0.39 per cent. But in Portugal the death rate was 2.64 per cent; in the Philippines 2.84 per cent; and in India, 4.39 per cent.

Young adults were hit especially hard; 1.6 per cent of men and 1.2 per cent of women between 20 and 30 died, according to data from the 13 countries that compiled age-specific mortality figures.

The team used these calculations to work out the impact today of a repeat of the pandemic. They factored in population increases and age structure, and per capita income, to work out where people would die and in what numbers.

If all the deaths occurred in a single year, worldwide mortal- ity would more than double in that year with 96 per cent of deaths outside the OECD rich-nation grouping.

There are many uncertainties. Global mean incomes are much higher now, and medical care much better. Many deaths in 1918 were the result of bacterial pneumonia which today could be countered by anti- biotics. Antivirals and vaccination also might help, but both would benefit richer countries more — where the toll is expected to be lower anyway.

Professor Murray is clear about the study’s implication. “International attention needs to focus on how we can protect the poorer countries should this virus recur.”