Question: What diagnoses apply to West Nile virus with encephalitis and post-encephalitis headache? The patient was discharged from the hospital and readmitted two days later with post-encephalitis headache. Florida Subscriber Answer: Begin with the diagnoses of 066.41 (West Nile fever with encephalitis) and 066.49 (West Nile fever with other complications); be sure to report additional codes explaining the complications, as ICD-9 directs. For the readmission, submit 784.0 (Headache).