The latest deaths from the H5N1 strain occurred in Azerbaijan, where five have died since February, the WHO reported.
The virus cannot pass easily from one person to another but there are fears it could mutate, triggering a pandemic.
US scientists have confirmed the H5N1 virus has evolved into two genetically distinct strains, potentially increasing the risk to humans.
The team from the US Centers for Disease Control and Prevention (CDC) also said this could complicate the search for an effective vaccine.
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