2009 swine-flu death toll 10 times higher than thought

The 2009 swine-flu pandemic may have killed up to 203,000 people worldwide - 10 times higher than the initial estimates by the WHO, a new analysis by an international group of scientists has found.

The research team consisting of more than 60 collaborators in 26 countries found that the pandemic virus caused up to 203,000 respiratory deaths around the world.

"This study confirms that the H1N1 virus killed many more people globally than originally believed," said lead author, Lone Simonsen, from George Washington University.

"We also found that the mortality burden of this pandemic fell most heavily on younger people and those living in certain parts of the Americas," said Simonsen.

The WHO, which funded the new study, had reports of 18,449 laboratory-confirmed deaths from the 2009 flu pandemic, but that is widely regarded as a low number because it is based only on people with confirmed cases of H1N1.

This study shows that the actual death toll was much higher than the official count because most infected people never got an H1N1 lab test.

The researchers obtained weekly virology data from the WHO and actual mortality data from 21 countries accounting for about 35 per cent of the world's population.

They used the information to estimate the number of respiratory deaths, which often occur when H1N1 gets into the lungs and causes pneumonia, in each of those 21 countries.

They then used a novel statistical procedure to project those results to the rest of the countries in the world.

The team found that when the H1N1 deaths due to cardiovascular disease and other causes are included, the 2009 pandemic toll might be as high as 400,000.

The team discovered that an estimated 62 to 85% of those who died in the 2009 pandemic were younger than age 65.

That high death toll for younger people is in marked contrast to that caused by seasonal influenza, which mostly targets seniors.

The high casualty rate for people in their prime translates to a bigger burden on individuals and society as younger victims often mean more productive years of lost life, the study authors said.

This study also showed a striking regional pattern as H1N1 swept through certain countries, leaving a substantial number of deaths in its wake.

For example, the researchers found an almost 20-fold higher mortality rate in some countries in the Americas with Mexico, Argentina and Brazil showing the highest respiratory death rates in the world. In contrast, the toll was far lower in New Zealand, Australia and most parts of Europe.

The study appears in the journal PLOS Medicine.