Polio affected spine. Light micrograph of a section through the cervical (neck) spine of a patient with poliomyelitis, or infantile paralysis. Poliomyelitis is caused by the polio virus. This case was caused by the type III (Leon) strain of the virus. In severe cases of the disease the virus infects the central nervous system (CNS) causing inflammation of nervous tissue and cell death, seen here as white gaps in the tissue. The death of the neurons (nerve cells) causes weakness in the muscles that they serve and can lead to paralysis. Vaccination, which started in the 1950s, has been successful in controlling the disease. It has now been eliminated from Europe.