Viruses can be small.Logical formLearned from19 sentences. A virus can be (bird flu).Logical formLearned from19 sentences. Mosquitoes may transmit a virus.Logical formLearned from19 sentences. Scientists may identify a virus.Logical formLearned from19 sentences. An infection may be caused by a virus.Logical formLearned from19 sentences. A virus may attack a heart.Logical formLearned from19 sentences. Viruses may circulate.Logical formLearned from19 sentences. A human (immunodeficiency virus) may weaken an immune system.Logical formLearned from19 sentences. (Flu viruses) may change.Logical formLearned from19 sentences. Virus may undergo a discovery.Logical formLearned from19 sentences. A child may be infected with a virus.Logical formLearned from19 sentences. A virus can be crippled.Logical formLearned from19 sentences. Viruses may cause a common cold.Logical formLearned from19 sentences. A mutation can be in a virus.Logical formLearned from19 sentences. Viruses can be fatal.Logical formLearned from19 sentences.