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Sunday, November 28, 2021

An Expert Explains: How is poliovirus similar (or different) to a coronavirus

Poliovirus was first isolated in 1909 by Karl Landsteiner and Erwin Popper and the first human coronavirus was isolated in 1933 by Leland David Bushnell and Carl Alfred Brandley.

Written by Dr Pavithra Venkatagopalan |
Updated: October 26, 2021 11:12:51 am
Polio drops being administered to one of the children during Nationwide Pulse Polio Drive at Sukhna Lake in Chandigarh on Sunday, January 31, 2021. (Express File Photo by Kamleshwar Singh)

In a world overwhelmed by the current Covid-19 pandemic, it is easy to forget about the existence of other viruses which can cause serious illness. One such virus that has affected our lives since the times of the Egyptian civilisation is the poliovirus. Every year, October 24 is marked as World Polio Day in celebration of the birth of Jonas Salk, the American researcher who developed the first polio vaccine in 1955.

The poliovirus is the simplest known human virus. It is very small at only 30 nanometers. In comparison, SARS-CoV-2 is a slightly larger virus at about 100 nanometers.

Poliovirus was first isolated in 1909 by Karl Landsteiner and Erwin Popper and the first human coronavirus was isolated in 1933 by Leland David Bushnell and Carl Alfred Brandley.

Poliovirus causes a disabling and life-threatening disease called poliomyelitis. The virus spreads from person to person and can infect a person’s spinal cord, causing paralysis. In about 25 per cent of all people infected with polio, it causes very mild flu-like symptoms including sore throat, fever, tiredness, nausea, headache, and stomach for about 2- 5 days and they make a full recovery.

However, in a smaller portion, the infected individuals can develop other symptoms like ‘pins and needles’ or a sensation of tingling or prickling in their arms and legs, meningitis and paralysis of the arms and legs. Children under the age of five are highest at risk of developing serious poliovirus-related complications, which affects their quality of life.

Poliovirus is highly contagious and can easily spread from person to person – the R-naught value, that is, the number of people one infected individual can infect for polio is 5-7. For Covid-19, the R-naught value is 1.4 to 3.9.

Poliovirus spreads by person-to-person contact, especially via the faecal-oral route. Poor hand hygiene, lack of access to clean water, improper sewage systems are the most common reasons for the incidence and transmission of polio. However, in the 1950s, the first polio vaccine was invented by Jonas Salk. This was a very safe and effective inactivated poliovirus vaccine, administered by injection.

While highly effective, in those times, the availability of disposable syringes was rare, and the speed of immunisation was low. Another polio vaccine, invented by Albert Sabin in 1961, was called the Oral Polio vaccine (OPV). This was more easily administered to large numbers of people with ease. A combination strategy was determined, and mass administration began. Polio eradication is one of the most ambitious global health initiatives in history, and polio will be only the second human disease in history to be eradicated (the first was smallpox).

Today, the only places in the world where wild polio exists are Pakistan and Afghanistan. The successful use of this vaccine reduced the number of polio cases from 3.5 lakh in 1988 to 33 in 2018.

Because polio is highly contagious, no one is safe until everyone is vaccinated. Since the introduction of the Global Polio Eradication Initiative (GEPI) in 1988, the rigorous efforts of the Ministry of Health and family welfare for surveillance of sewage samples for poliovirus and a robust vaccination program as a public-private partnership with Rotary International has made this vaccination program a resounding success. As of March 27, 2014, India has been declared polio-free.

The science of vaccine development and our understanding of our immune system has improved vastly since the development of the polio vaccine. In the field of vaccinology, researchers have been working on how to design and develop safer, effective, cheaper vaccines for decades.

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Various safe and effective vaccines against Covid-19 have been developed across the globe using classical vaccine development technology as well as more modern state-of-the-art technology.

Designing a strategy, developing a vaccine, testing its safety and efficacy is a laborious, time-consuming and expensive process. However, in the times of Covid-19, vaccine developers had decades of data, abundant volunteers, and sufficient funding to study the effectiveness of the different vaccines. Collaboration between scientists, regulatory agencies, vaccine manufacturers has paved the way for us to have multiple vaccines against Covid-19 in such a short time.

The writer is Director, Covid Task Force, Awareness, Rotary Club of Madras Next Gen.

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