One was reported in the state of Rio de Janeiro, and seven in neighboring Espirito Santo, both in Brazil's southeast.
The measure extends an already-enacted suspension on expos and fairs involving birds.
Agriculture Minister Carlos Favaro said it would also "mobilize resources" to take preventive measures to contain the virus.
Brazil, the world's biggest chicken exporter last year, supplies around 35 percent of all poultry on the international market.
The current bird flu outbreak began in Canada in 2021, then spread to the United States and Latin America.
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