A new report on deaths linked to the 2009 H1N1 swine flu pandemic shows the total number of deaths to be more than ten times higher than reported by the World Health Organization.

The study also discovered that respiratory deaths in the Americas can be 20 times higher than the death rates in Europe.

Examining only deaths from pneumonia that could have been connected to the flu, the study showed Mexico, Argentina and Brazil had the highest death rates from the pandemic. The toll was significantly lower in New Zealand, Australia and in most of Europe.

“[The report] confirms that the H1N1 virus killed many more people globally than originally believed,” study author Lone Simonsen of George Washington University said. “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.”

The World Health Organization said in 2010 the death toll from H1N1 was around 18,500 but noted their total was limited to laboratory confirmed testing.