poliomyelitis /pō′lē·ōmī′əlī″tis/ [Gk, polios + myelos, marrow, itis] , an infectious disease caused by one of the three polioviruses. Asymptomatic, mild, and paralytic forms of the disease occur. Several factors influence susceptibility to the virus and the course of the disease: More boys than girls are severely affected, stress increases susceptibility, more pregnant than nonpregnant women acquire the paralytic form of the disease, and the severity of the infection increases with age. It is transmitted from person to person through fecal contamination or oropharyngeal secretions. The disease is prevented by vaccination. Also called polio. See also acute atrophic paralysis, poliovirus. ▪ OBSERVATIONS: Asymptomatic infection has no clinical features, but it confers immunity. Abortive poliomyelitis lasts only a few hours and is characterized by minor illness with fever, malaise, headache, nausea, vomiting, and slight abdominal discomfort. Nonparalytic poliomyelitis is longer lasting and is marked by meningeal irritation with pain and stiffness in the back and by all the signs of abortive poliomyelitis. Paralytic poliomyelitis begins as abortive poliomyelitis. The symptoms abate, and for several days the person seems well. Malaise, headache, and fever recur; pain, weakness, and paralysis develop. The peak of paralysis is reached within the first week. In spinal poliomyelitis, viral replication occurs in the anterior horn cells of the spine, causing inflammation, swelling, and, if severe, destruction of the neurons. The large proximal muscles of the limbs are most often affected. Bulbar poliomyelitis results from viral multiplication in the brainstem. Bulbar and spinal poliomyelitis often occur together.
