Poliovirus is an RNA virus which belongs to the Picornaviridae Family of enteroviruses (Entrovirus is the scientific name for any virus that is transmitted through the intestine). The disease caused by Poliovirus is called Poliomyelitis, Polio or Infantile Paralysis.

Poliovirus History

1. Poliovirus disease (Polio) was first described in Britain in 1789 by Michael Underwood
2. Jonas Salk in the 1954, developed the inactivated poliovirus vaccine (IPV) to the three infectious forms of the poliovirus
3. In 1959, Albert Sabin discovered the live attenuated oral poliovirus vaccine (OPV) but this is not used in routine immunization except in epidemics

Poliovirus Types/Classification

1. Poliovirus type 1 this has the highest rate of paralysis and commonly cause epidemics
2. Poliovirus type 2
3. Poliovirus type 3

Poliovirus Transmission

Poliovirus is transmitted through the feco-oral route. This means that you get infected with the Poliovirus when you eat food contaminated with feces containing the virus. Only humans can transmit the poliovirus as only humans harbor the virus no animals involved. Apart from eating food contaminated with feces containing the poliovirus, it can also be spread by coughing or sneezing. Replication of the poliovirus occurs in the pharynx or the gastrointestinal tract before invasion of the adjacent lymph tissue.

Poliovirus Life cycle and Pathogenesis

The poliovirus is found in the throat and feces of humans and gains entry into the body the oropharynx by ingestion of fecal contaminated food or inhalation of droplets. Replication of the poliovirus then occurs in the intestine with invasion of the bloodstream, which then leads to spread to the CNS and subsequent selective attack on the cells of the anterior (motor) and lateral horns of the spinal cord and the motor cells of the brain stem. Most of the attacked cells recover from the inflammatory edema but some are destroyed leading to the paralysis observed.

Poliovirus Characteristics

1. Polioviruses have affiliation to the nervous system, especially the cells of the anterior horn of the spinal cord and cranial nerve motor neurons.
2. Poliovirus replicates optimally at 37C
3. Poliovirus can easily be killed by heat, ultraviolet light and chemicals such as formaldehyde and chlorine
4. Poliovirus can withstand acidic environment within the pH range of 3 to 5; this is the reason why they can survive exposure to gastric acid

Poliovirus Structure

The Poliovirus is icosahedral in shape (it has 20 faces and 30 edges with 12 vertices making the structure of the polygon of the Poliovirus) and has no envelope. It is an RNA virus and measures about 30nm in size

Symptoms of Poliovirus infection (Major syndromes manifested by infection with Poliovirus)

1. Paralysis
2. Aseptic meningitis
3. Encephalitis

Poliovirus Diagnosis

1. Poliovirus can be diagnosed by the polymerase chain reaction (PCR)
2. The virus can also be isolated in stool culture

Poliovirus Treatment

There is currently no cure for Poliovirus infection; Supportive treatment to help the body fight the infection as well as Physiotherapy to reduce disability caused by deformities is the modality taken while managing polio victims. Ventilators are also used to help in breathing when the respiratory muscles are affected.

Poliovirus Facts

1. Poliovirus has the ability to infect cells of Peyer’s patches of the intestine and the Motor neurons
2. 95% of infections with Poliovirus do not cause paralysis, only a few lead to paralysis
3. Infection with the Poliovirus has an incubation period of 7 to 14 days
4. Some children may have polio but may not show symptoms, such people are said to be Asymptomatic but they can still transmit the infection.
5. There is no cure for Poliovirus infection except supportive treatment given to help the body fight the virus or physiotherapy to reduce deformities or when deformities have formed
6. The last cases of poliovirus infection in the Unites States of America caused by wild poliovirus occurred in 1979

Prevention of Poliovirus Infection

1. Immunization of children using poliovirus vaccines
2. Encourage good hygiene
3. Enlightenment of the public especially in endemic areas where Poliovirus has not been eradicated