Meanwhile, scientists in China are worried about a new strain of bird flu.
This one is called the H7N9 virus and it's already killed 36 people in that country.
Researchers there say many patients have recovered after taking anti-viral drugs like tamiflu. But in some cases, that's not working, indicating this H7N9 appears to be building some resistance to the drug.
This study was led by researchers at Shanghai Health Clinical Centre and published in 'The Lancet'.
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