A subtype may pertain-to a (bird flu virus).Logical formLearned from10 sentences. Persons may be infected with (bird flu).Logical formLearned from10 sentences. A (bird flu outbreak) may be reported.Logical formLearned from10 sentences. (Bird flu) may infect humans.Logical formLearned from10 sentences. (Bird flu) may undergo a reappearance.Logical formLearned from10 sentences. (Bird flu) may kill.Logical formLearned from10 sentences. Cases of (bird flu) may be reported.Logical formLearned from10 sentences. A (bird flu case) can be in a country.Logical formLearned from10 sentences. (Bird flu) may break_out in a country.Logical formLearned from10 sentences. Some poultry may be infected with (bird flu).Logical formLearned from10 sentences. A flu may circulate.Logical formLearned from10 sentences. Some (flu pandemic) can be in a continent.Logical formLearned from10 sentences. Flu may be caused by a virus.Logical formLearned from10 sentences. A (flu vaccine) can be effective.Logical formLearned from10 sentences. A (flu immunization) can be annual.Logical formLearned from10 sentences.