Polio is a highly infectious disease caused by a virus that invades the nervous system, potentially leading to paralysis or death. The disease, primarily affecting children under 5 years of age, has three distinct strains: Wild Poliovirus type 1 (WPV1), Wild Poliovirus type 2 (WPV2), and Wild Poliovirus type 3 (WPV3). All three strains share identical symptomatic traits; however, significant genetic and virological differences exist that make their eradication necessary on an individual basis.
Transmission and Symptomatology of Polio
Polio transmission occurs predominantly through person-to-person contact, mainly via the faecal-oral route. It can also spread through contaminated food or water. The virus multiplies within the intestine, from where it can penetrate the nervous system and induce paralysis. Most infected individuals do not experience illness, while some may exhibit minor ailments such as fever, fatigue, nausea, headache and muscle pain. In rare cases, permanent loss of muscle function or paralysis can occur. Polio can be fatal if the muscles required for breathing become paralyzed or the brain becomes infected.
Prevention and Vaccination
Despite the lack of a cure for Polio, preventive measures exist in the form of immunisation. Two main vaccines are available: Oral Polio Vaccine (OPV) and Injectable Polio Vaccine (IPV). OPV is administered orally, initially as a birth dose, followed by primary doses at 6, 10 and 14 weeks, and a booster dose at 16-24 months. IPV is administered as an additional dose with the third DPT (Diphtheria, Pertussis, Tetanus) dose under the Universal Immunisation Programme (UIP).
Recent Polio Outbreaks
Polio outbreaks in 2019 were reported in various countries, including the Philippines, Malaysia, Ghana, Myanmar, China, Cameroon, Indonesia and Iran, with most cases identified as vaccine-derived. According to the World Health Organisation (WHO), strains of the virus in the vaccine can mutate to cause infections if allowed to circulate in an under-immunised population for at least 12 months.
India’s Polio-Free Status
India received certification as polio-free from the WHO in 2014, following three years without cases. This milestone was achieved largely due to the successful Pulse Polio Campaign, which administered polio drops to every child. The last case of wild poliovirus in India was detected on 13th January 2011.
Global and Indian Measures for Polio Eradication
The Global Polio Eradication Initiative (GPEI) was established in 1988 by national governments and the WHO. As a result, 80% of the global population now inhabits certified polio-free regions. World Polio Day is observed annually on October 24 to maintain vigilance in the fight against the disease. In India, the Pulse Polio Programme aimed to achieve 100% coverage with the Oral Polio Vaccine. The Intensified Mission Indradhanush 2.0 marked the 25th anniversary of the Pulse Polio Programme with a nationwide immunisation drive. The Universal Immunisation Programme (UIP), launched in 1985, aims for rapid immunisation coverage improvement, enhanced service quality, reliable cold chain system establishment, district-wise performance monitoring, and self-sufficiency in vaccine production.
