• An unvaccinated young adult from New York recently contracted polio, the first US case in nearly a decade. The patient, who lives in Rockland County, had developed paralysis. The person developed symptoms a month ago and did not recently travel outside the country.

• Polio was once one of the nation’s most feared diseases, with annual outbreaks causing thousands of cases of paralysis, many of them in children.

• Vaccines became available starting in 1955, and a national vaccination campaign cut the annual number of US cases to less than 100 in the 1960s and fewer than 10 in the 1970s, according to the Centers for Disease Control and Prevention.

• In 1979, polio was declared eliminated in the US, meaning there was no longer routine spread. 

• Rarely, travellers have brought polio infections into the US. The last such case was in 2013.

• Polio is endemic in Afghanistan and Pakistan, although numerous countries in Africa, the Middle East and Asia have also reported cases in recent years.

Key points on polio:

• Poliomyelitis (polio) is a highly infectious viral disease that largely affects children under five  years of age. The virus is transmitted by person-to-person spread mainly through the faecal-oral route or, less frequently, by a common vehicle (for example, contaminated water or food) and multiplies in the intestine.

• It can infect a person’s spinal cord, causing paralysis and possibly permanent disability and death.

• In 1988, the World Health Assembly adopted a resolution for the worldwide eradication of polio, marking the launch of the Global Polio Eradication Initiative, spearheaded by national governments, WHO, Rotary International, the US Centers for Disease Control and Prevention (CDC), UNICEF, and later joined by the Bill & Melinda Gates Foundation and Gavi, the Vaccine Alliance. 

• Wild poliovirus cases have decreased by over 99 per cent since 1988, from an estimated 350,000 cases in more than 125 endemic countries then to 175 reported cases in 2019. 

• Of the three 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. Both strains have officially been certified as globally eradicated. At present, wild poliovirus type 1 affects two countries —  Pakistan and Afghanistan.

• Economic modelling has found that the eradication of polio would save at least $40–50 billion, mostly in low-income countries.

What is vaccine-derived poliovirus?

A vaccine-derived poliovirus (VDPV) 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.

Eradication of polio in India

India was certified polio-free by the Regional Polio Certification Commission in 2014. Last case of wild poliovirus in the country was reported in 2011 from Howrah, West Bengal and no wild poliovirus cases have been reported thereafter from any state/UT.

To maintain the polio-free status of the country, the government is taking following measures:  

• Population immunity against polio is being maintained by observing polio campaigns every year. 

• National Immunisation Days (NIDs) are held across India twice a year, with the government of India setting out to give two drops of oral polio vaccine (OPV) to every child in the country under the age of five. The scale is extraordinary, with more than 17.2 crore children immunised by 2.3 million vaccinators who visit every house in every city, town and village across the country. 

• Several Sub-National Immunisation Days (SNIDs) are also held annually in the highest-risk states. 

• Inactivated Polio Vaccine (IPV) has been introduced across the country to further boost the population immunity as additional protection against polio.

• Vaccination to international travellers to and from polio endemic countries and continuous vaccination at the international borders of India are being carried out throughout the year to mitigate risk of importation.

• Sensitivity of polio surveillance is maintained through Acute Flaccid Paralysis (AFP) surveillance in human and environment surveillance to detect any polio threat as early as possible and respond quickly to mitigate the risk of circulation.

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