Complications of smallpox infections include panophthalmitis, keratitis, corneal ulcers, blindness, osteomyelitis, arthritis, orchitis, and encephalitis [65] . Delirium occurs in approximately 15% of patients [8] . Encephalitis is reported to occur in 1 of 500 cases of variola major, and 1 of 2000 of variola minor, usually developing during the stages of the rash. Psychosis and seizures may occur [66] .