Polio

Subject – Science and Tech

Context– The Health Ministry has decided to vaccinate returnees from Afghanistan with free polio vaccines as a preventive measure.

Concept –

Polio also called as Poliomyelitis. It is a viral disease that destroys the nerve cells present in the spinal cord, causing paralysis or muscle weakness to some parts of the body.
It is a contagious disease affecting the nervous system and is caused by Picornaviridae – a poliovirus.
The virus is transmitted by person-to-person through the following ways –
- 1) Through the faecal-oral route.
- 2) By contaminated water or food.
This virus primarily grows and multiplies in the intestine, from where it can attack thenervous system and will cause polio and paralysis on an advanced level.
There are three individual and immunologically distinct wild poliovirus strains:
- Wild Poliovirus type 1 (WPV1)
- Wild Poliovirus type 2 (WPV2)
- Wild Poliovirus type 3 (WPV3)
Symptomatically, all three strains are identical, in that they cause irreversible paralysis or even death.
However, there are genetic and virological differences, which make these three strains separate viruses which must each be eradicated individually.
WPV2 and WPV3 have been eradicated globally but WPV1 remains in circulation in Afghanistan and Pakistan.
- WPV2 was eradicated in 1999.
There is no cure, but it can be prevented through immunisation.

Vaccines:

Oral Polio Vaccine (OPV):It is given orally as a birth dose for institutional deliveries, then primary three doses at 6, 10 and 14 weeks and one booster dose at 16-24 months of age.
Injectable Polio Vaccine (IPV):It is introduced as an additional dose along with the 3^rd dose of DPT (Diphtheria, Pertussis and Tetanus) under the Universal Immunisation Programme (UIP).

Polio Eradication:

For a country to be declared polio-free, the wild transmission of all three kinds of Polioviruses has to be stopped.
For eradication, cases of both wild and vaccine-derived polio infection have to be reduced to zero.
Eradication of a disease refers to the complete and permanent worldwide reduction to zero new cases through deliberate efforts. If a disease has been eradicated, no further control measures are required.
However, elimination of a disease refers to reduction to zero or a very low defined target rate of new cases in a defined geographical area. It requires continued measures to prevent re-establishment of disease transmission.

Polio in India:

India received polio-free certification by the WHO in 2014, after three years of zero cases.
The last case due to wild poliovirus in the country was detected on 13th January 2011.