A source may pertain-to a virus.Logical formLearned from388 sentences. A virus can be nasty.Logical formLearned from385 sentences. Spread may pertain-to a virus.Logical formLearned from380 sentences. A virus can be infectious.Logical formLearned from372 sentences. A virus may undergo a discovery.Logical formLearned from358 sentences. A spread may pertain-to a virus.Logical formLearned from356 sentences. A virus can be fatal.Logical formLearned from353 sentences. Symptoms may pertain-to a virus.Logical formLearned from352 sentences. A virus may cause a disease.Logical formLearned from345 sentences. A virus may pertain-to a person.Logical formLearned from340 sentences. Infection can be with a virus.Logical formLearned from337 sentences. Strains may pertain-to a virus.Logical formLearned from329 sentences. Carriers may pertain-to a virus.Logical formLearned from327 sentences. A male may have a virus.Logical formLearned from301 sentences. A virus can be pathogenic.Logical formLearned from298 sentences.