Polio Virus

Polio Virus


Characteristics of Poliovirus

  • Family: Picornaviridae
  • Genus: Enterovirus
  • Poliovirus are small, hexagonal, +ssRNA virus
  • Symmetry: Icosahedral capsid composed of 60 capsomere
  • Each capsomere consists of four viral protein (VP1- VP4)
  • Size: 22-30nm
  • Shape: spherical
  • Genome: positive sense single stranded RNA (+ssRNA).
  • The genome is polyadenylated at 3’ end and
  • Non-enveloped

Other characteristics of poliovirus

  • Poliovirus can survive for 4-6 months in cold water.
  • It can be inactivated by pasteurization temperature, 0.3% formaldehyde, 0.1M HCL, residual cholorine of (0.3-0.5) ppm
  • It is resistant to lipid soluble agents such as Ether, Chloroform, bile and proteolytic enzymes of intestine
  • It can survive in faeces for months at 4° C and for years at -20°
Epidemiology
  • WHO recorded Polio cases have decreased by over 99% since 1988, from an estimated 350 000 cases in more than 125 endemic countries then, to 37 reported cases in 2016.
  • Of the 3 strains of wild poliovirus (type 1, type 2, and type 3), wild poliovirus type 2 was eradicated in 1999 and no case of wild poliovirus type 3 has been found since the last reported case in Nigeria in November 2012.
  • Pakistan, Afghanistan and Nigeria are endemic to poliovirus

Serotypes of Poliovirus:

  • On the basis of neutralization test poliovirus is divided into three serotypes.

Poliovirus 1: 

  • Most common and virulent type.
  • Frequently isolated from patients with poliomyelitis and causes epidemics

Poliovirus 2: 

  • Usually associated with endemic infection

Poliovirus 3: 

  • Causes occasional endemic infection

Mode of transmission

  • Human are the only natural host for Poliovirus
  • primarily by: Faeco-oral route by Ingestion of virus contaminated food and water
  • In the faces, the virus is excreted commonly for 2 to 3 weeks, sometimes as long as 3 to 4 months
  • Droplet infection, inhalation
Reservoir of infection
  • Man is the only reservoir. Most infections are subclinical and play a dominant role in spread of infection.
  • It is estimated that for every clinical case, there may be 1000 subclinical cases in children and 75 in adults.

 Infectious material

  •  Feces and oropharyngeal secretion. 

 Period of communicability

  • to 10 days before and after onset of symptoms. 

Age

  •  6 months to 3 years 

Sex

  • More in males
Exam Question
 
  • Poliovirus 1: 
  • Most common and virulent type.
  • Frequently isolated from patients with poliomyelitis and causes epidemics

Mode of transmission

  • Human are the only natural host for Poliovirus
  • primarily by: Faeco-oral route by Ingestion of virus contaminated food and water
  • In the faces, the virus is excreted commonly for 2 to 3 weeks, sometimes as long as 3 to 4 months
  • Droplet infection, inhalation
  • Reservoir of infn is the only reservoir. Most infections are subclinical and play a dominant role in spread of infection.
  • It is estiection

Mamated that for every clinical case, there may be 1000 subclinical cases in children and 75 in adults.

Period of communicability

  • to 10 days before and after onset of symptoms. 
Don’t Forget to Solve all the previous Year Question asked on Polio Virus

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