Swine flu death toll could be as high as 600,000, say experts

Nearly 600,000 people could have died worldwide in the 2009 swine flu pandemic – almost 30 times the number previously believed.

Between April 2009 and August 2010, 18,500 H1N1 deaths were confirmed in laboratories.

But lab-confirmed deaths are generally known to be significantly lower than the true figure, and new research estimates the actual number of deaths to be between 151,700 and 575,400.

The results suggest eight out of ten deaths were people aged under 65, unlike the seasonal flu which tends to affect the elderly.

Researchers also say that 59 per cent of the deaths may have occurred in south-east Asia and Africa, with the highest mortality rates occurring in Africa.

Dr Fatimah Dawood, of the US Centres for Disease Control and Prevention, said: “We hope that this work can be used not only to improve influenza disease modelling globally, but to improve the public health response during future pandemics in parts of the world that suffer more deaths, and to increase the public’s awareness of the importance of influenza prevention.”

The new estimates of flu deaths are based only on data from countries that hold information on the numbers of people who developed flu symptoms, and the numbers of deaths among flu cases during the H1N1 pandemic.

However, shortcomings in the availability of high-quality data for most countries affected by the pandemic may affect the accuracy of the new estimates, with the authors pointing out that the lack of data is particularly pronounced for low and middle-income countries. Dr Dawood added: “Continued efforts to strengthen influenza surveillance worldwide, particularly for influenza-associated mortality, are needed both to guide seasonal influenza prevention strategies and to build influenza surveillance systems to provide better and more timely and globally representative data for influenza-associated mortality during future pandemics.”

Dr Cecile Viboud of the National Institutes of Health, Maryland, said the new figures compare well with independent estimates of H1N1 deaths in individual countries. But some are significantly lower than independent estimates in countries such as Mexico.

Dr Viboud said: “These results are likely to be refined as more studies from low-income and middle-income regions become available, particularly from China and India, where about a third of the world’s population live but where little information is available about the burden of influenza.” The results are published in The Lancet.