A prevalence of a virus can be low.Logical formLearned from15 sentences. A virus may undergo a reintroduction.Logical formLearned from15 sentences. Strains may pertain-to a (flu virus).Logical formLearned from15 sentences. A mother may pass a virus to a child.Logical formLearned from15 sentences. A virus may change a form.Logical formLearned from15 sentences. A (death toll) can be from a (virus outbreak).Logical formLearned from15 sentences. A mutation of a (bird flu virus) may create a pandemic.Logical formLearned from15 sentences. Strains may pertain-to an (influenza virus).Logical formLearned from15 sentences. A march may pertain-to a virus.Logical formLearned from15 sentences. A virus may get a hold on cities.Logical formLearned from15 sentences. A virus can be a type.Logical formLearned from15 sentences. Migratory birds may take a virus to a continent.Logical formLearned from15 sentences. A total of some persons may die from a virus.Logical formLearned from15 sentences. Concerns can be about a spread of a virus.Logical formLearned from15 sentences. An emergence may pertain-to a virus.Logical formLearned from15 sentences.