A (polio virus) may attack.Logical formLearned from17 sentences. A form of a virus may cross with (flu strains).Logical formLearned from17 sentences. Defenses can be against viruses.Logical formLearned from17 sentences. A vaccination can be against a virus.Logical formLearned from17 sentences. A virus may reproduce itself.Logical formLearned from17 sentences. A virus can be transmissible among humans.Logical formLearned from17 sentences. A virus may remain a mystery.Logical formLearned from17 sentences. A test may detect a virus.Logical formLearned from17 sentences. An onset may pertain-to a virus.Logical formLearned from17 sentences. A virus may be isolated in a district of a country.Logical formLearned from17 sentences. A (death toll) can be from a virus.Logical formLearned from17 sentences. Some persons may be diagnosed with a virus.Logical formLearned from17 sentences. Cases may be caused by a virus.Logical formLearned from16 sentences. Deaths may be associated with a virus.Logical formLearned from16 sentences. A pandemic may be caused by a virus.Logical formLearned from16 sentences.