Science and technology
wild polio
✓Africa has been declared free from wild polio by the independent body, the Africa Regional Certification Commission.
✓ Now only the vaccine-derived polio virus remains in Africa.
✓A region is certified as free of wild polio after three years have passed without the virus being detected in any of its countries.
✓ Nigeria is the last African country to be declared free from wild polio.
✓Wild polio is still present in Pakistan and Afghanistan.
*Vaccine derived poliovirus:
It is a strain of the weakened poliovirus that was initially included in oral polio vaccine (OPV) and that has changed over time and behaves more like the wild or naturally occurring virus.
✓This means it can be spread more easily to people who are unvaccinated against polio and who come in contact with the stool or respiratory secretions, such as from a sneeze, of an infected person. These viruses may cause illness, including paralysis.
✓Oral polio vaccine (OPV) contains an attenuated (weakened) vaccine-virus, activating an immune response in the body. When a child is immunized with OPV, the weakened vaccine-virus replicates in the intestine for a limited period, thereby developing immunity by building up antibodies.
✓During this time, the vaccine-virus is also excreted. In areas of inadequate sanitation, this excreted vaccine-virus can spread in the immediate community (and this can offer protection to other children through ‘passive’ immunization), before eventually dying out.
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