Masaio Ishizuka, a senior epidemiologist at the Sao Paulo University, said evidence suggests migratory birds have now infected local Brazilian species, making the bird flu virus endemic in the world's largest chicken exporter, which accounts for 39% of global trade.

The Brazilian Agriculture Ministry has updated on Wednesday the list of countries that have placed restrictions on chicken trade with Brazil, the world's largest exporter, after it confirmed its first case of bird flu on a commercial farm in May.

FileBrazil on Wednesday declared its commercial flocks free of the bird flu virus after observing a 28-day period without any new commercial farm outbreaks, the country's ministry of agriculture said.