The WHO doesn’t know for sure... The article would leave you to believe the data is accurate, but it isn’t.
The WHO sent out the request to countries to scale down on taking data related to the H1N1 virus.
http://www.nytimes.com/2009/07/17/world/17flu.html?_r=1
It could be even higher in Brazil.
Thats it. They don’t know. CFR is difficult to calculate. But relative severity can be judged. Or could be. As this progresses, it will be harder and harder to test nearly enough people to get a handle on it. But right now I see no evidence Brazil has a greater CFR than other countries. Which leads to why the theory its mutating into a worse form there?