Polio has occurred for thousands of years in all parts of the world. The bone formation of an Egyptian skeleton of the period of 3700 B.C. indicates the effects of polio, as does an Egyptian plaque from 1300 B.C....
Polio has had many labels; poliomyelitis, infantile paralysis, Heine-Medin disease, and poliomylelopathy. Poliomyelitis is a combination of two Greek words: Polios or gray, denoting the gray matter of the nervous system, and myelos or marrow, denoting the myelin sheath around certain nerve fibres.
The recording of polio as a disease dates from the late 18th century. By the early 19th century it was reported as being widespread in Europe and India. It was regarded as ubiquitous and caused by teething, foul bowels, or fever.
Presently, it is known that the infection is primarily an inapparent one involving the alimentary tract, that paralytic polio is a relatively uncommon complication, and that silent infection in childhood provides long-lasting protection. The disease is spread by asymptomatic persons through the shedding of the virus from the throat and intestinal tract. Dissemination of the disease is enhanced by poor sanitation, crowding, and low standards of personal hygiene such as those that are common in many tropical and subtropical areas. It is still a widespread problem of endemic proportions in parts of the Eastern Hemisphere.
*1. Immunological Types of Virus
The poliomyelitis virus is an obligate intracellular parasite which has been classified into three main types: Brunhilde - named after the Rhesus monkey in which the virus was first identified, Lansing - isolated from a fatal case of bulbar polio in Lansing, Michigan and Leon - identified in a child named Leon during the Los Angeles epidemic. Because of these three separate immunological types, in theory, you can get polio three times.
*2. Type Based on Severity of Infection
Probably the most common type of poliomyelitis is the form least identified by the general public. It is known as abortive polio and is difficult to diagnose, since the symptoms are often overlooked. These symptoms may consist merely of headache, fever, vomiting, sore throat, or an upset stomach. There are no evidences of paralysis. It is this form that helps to bring about lifelong immunity for a vast number of person. It is not known how many mild cases of this disease occur, nor the ratio of these mild abortive cases to paralytic cases.
If, on the other hand, the virus on reaching the central nervous system carries on pronounced activity, it will bring on identifying symptoms of recognized poliomyelitis. First, it may cause merely a stiffness of the neck and back, but no clinically evident weakness. It is known that those with recognized and definite poliomyelitis, at least one-half get entirely well without any significant paralysis.
The most familiar and more dramatic, but fortunately the least common form of the disease, is paralytic poliomyelitis. Here large numbers of the nerve cells are rendered useless and the muscles which they innervate are unable to cause motion. A person may become paralyzed in the arms the legs, or other parts of the body. The disease may affect the muscles of respiration that cause the breathing action of the lungs.
*3. Types by Location in the Central Nervous System
At times the virus may settle in the region of the medulla, or "bulb," the thickened collection of nervous tissue at the upper end of the spinal cord. It is in bulb that many of the vital nerve centres of the body are lodged. When the infection localizes in this region, it is known as bulbar polio. The virus, lodging here, may affect the nerves controlling the muscles of the throat, thus making it impossible to swallow or to speak plainly. Lodging in the medulla, the virus could affect the breathing "centres." Bulbar poliomyelitis is very serious. However, this form of polio is fortunately relatively rarer than the spinal polio, where the infection localizes lower down in the spinal cord. Spinal polio is divided into two types: high spinal polio because the nerves controlling the muscles of breathing - diaphragm and intercostals - are located in the high spinal area: low spinal polio which involves
the lower limbs.
All these forms - spinal and bulbar - are the same illness, the only difference being in the location and the extent of damage done to the nerve cells which control the various muscle activities.
Reprint from Sappling's August 1994 (Post-Polio Network April, 1993)