Poliovirus is a deadly and highly contagious virus that spreads through direct or indirect human to human contact. However, what makes polio really fatal is the fact that it has no cure.
What causes polio?
The poliovirus is caused by small RNA based viruses of the enterovirus group of the Picornavirus family. With three different types, it can cause a wide range of health concerns in humans. The type 1 virus is the most severe and is responsible for about 85% of all paralysis resulting from the infection. These types are antigenically distinct virus strains and one form of infection or immunity does not protect against the other two types, but if immunity is developed for one or more of the three strains, immunity is permanent. The problem caused by these viruses is the killing of spinal cord cells.
What is the history of polio?
The first traces of poliovirus dates back six thousand-year-old Egyptian with malformed limbs but the first recorded evidence is from 1789. By 1951 the three types of poliovirus were identified and isolated a large-scale trial of the dead polio vaccine developed by Dr Jonas Salk. Later, in 1958, Dr Albert Sabin's live attenuated poliovirus oral vaccine came into effect.
How does the virus spread?
Polio viruses can only survive in humans and be transmitted through direct or indirect human contact. The indirect methods of transmission include any traces of faecal matter of an infected person finding its way into the food and water of a healthy individual. People working with polio patients and labs with poliovirus are susceptible to direct transmissions. Other modes of direct transmission are through cough or sneeze. War and lack of access to the vaccine are among the other major causes of polio spread in the world.
The virus enters the body through the nasal or oral cavity and keeps multiplying. As their numbers increase, the virus reaches the intestines and get absorbed into the blood and lymphatic system and ultimately take over the entire body. The incubation period between the virus entering the body and the symptoms becoming apparent is seven to fourteen days. Between this period a person can experience a number of symptoms that can ultimately lead to paralysis upon the destruction of the cells of the spinal cord. As the virus has three distinct strains, immunization against one strain does not guarantee protection against the two other types.
The World Health Organization has made the eradication of polio from the world a top priority. Although there has been a 99% decrease in polio infections around the world, Africa and the Middle Eastern countries have known polio infections. However, just like smallpox, eradication of the poliovirus seems extremely likely in the near future.