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Polio Virus History And Recent Outbreaks

Introduction

Polio is commonly used as a term for poliomyelitis. The term poliomyelitis was coined by German physician Adolph Kussmaul in 1874. Poliomyelitis is characterized by the inflammation of grey matter of the spinal cord which is evident by its etymology derived from Greek words polios meaning grey, myelos meaning marrow, and itis stands for inflammation. Poliomyelitis is a disease of the nervous system and is caused by poliovirus, a positive sense RNA virus belonging to the family Picornaviridae.

History Of Poliomyelitis

Poliomyelitis is an ancient disease that has been known to afflict mankind massively since the years of yore. Egyptian portraits from 1365-1405 BC illustrated infants and children with deformed limbs taking the support of sticks to walk. It was 1879 when English physician Michael Underwood first defined poliomyelitis as “debility of lower extremities” (Mehndiratta, Mehndiratta, and Pande, 2014)

Vaccination

For the eradication and prophylaxis of polio, vaccination was performed all around the globe, and most regions of the world were declared polio-free except a few developing countries where poliomyelitis is still endemic. Vaccines available for poliomyelitis are of two types, inactivated polio vaccine (IPV) or Salk vaccine developed by John Salk in 1955 and oral polio vaccine (OPV) that was developed by Albert Sabin that was made commercially available in 1961.OPV formulation contains the live attenuated virus. Both vaccines have their pros and cons. Salk vaccine(IPV) is safer as the virus is dead and can’t revert to its pathogenic form, causing vaccine-associated poliomyelitis(VAP), which has been reported in the case of the Sabin vaccine (OPV), but the Sabin vaccine has been experimentally shown to be more efficient. Due to the high incidences of VAP, many countries have started using relatively expensive IPVs. Four doses of vaccine are administered to children at the age of 2 months, four months, somewhere between 6-18 months, and 4-6 years of age (Cdc.gov, 2018).

Vaccination has proved to be very successful, and a huge reduction in the number of cases of poliomyelitis speaks for the achievements of immunization.

Recent Outbreaks

Despite all the hard work being done to eradicate poliomyelitis, it is still endemic in some developing countries of the world, e.g., Pakistan, Afghanistan, India, Nigeria, and a few others, and outbreaks occur frequently in countries that were once declared polio-free, too. In 2013, in Syria, a polio case was identified, and soon after, the number of cases increased to 10 and finally 35 (Akil and Ahmad, 2016). In 2014, 27 children were reported to be paralyzed by a virus 58 instances of Poliovirus type 2 were also reported in 2017.

Pathogenesis

The route of transmission of poliovirus is fecal-oral. After gaining entry into the body through the oral route, the Virus establishes and multiplies in the alimentary mucosa and probably in Peyer’s patches and tonsils. This is followed by viremia as the virus crosses the natural barriers to reach the bloodstream. Viremia facilitates the virus to invade the CNS either by crossing the blood-brain barrier or through peripheral nerves, and it replicates in the neurons, preferably in motor neurons (Nomoto, 2007). During the infection process, poliovirus deploys several strategies to evade the immune responses.

Signs And Symptoms

Most of the infected persons remain asymptomatic. Symptomatic persons fall into two major groups

1-Paralytic polio

2-Non-paralytic polio.

The symptoms of Nonparalytic or abortive poliomyelitis are fever, sore throat, headache, malaise, neck and back pain, and stiffness of muscles, and the symptoms usually subside within a few weeks. Rarely, paralytic poliomyelitis can occur with alarmingly serious symptoms such as loss of reflexes, severe myalgias, difficulty in breathing, and flaccid paralysis (Anthony N. van del, 2013). The disease may sometimes affect one side of the body relatively higher in intensity than the other.

References

Akil, L., & Ahmad, H. A. (2016). The recent outbreaks and reemergence of poliovirus in war and conflict-affected areas. International Journal of Infectious Diseases49, 40-46.

Cdc.gov. (2018). Vaccines: VPD-VAC/Polio/main page. [online] Available at: https://www.cdc.gov/vaccines/vpd/polio/index.html [Accessed 5 Apr. 2018].

Mehndiratta, M. M., Mehndiratta, P., & Pande, R. (2014). Poliomyelitis: historical facts, epidemiology, and current challenges in eradication. The Neurohospitalist4(4), 223-229.

Nomoto, A. (2007). Molecular aspects of poliovirus pathogenesis. Proceedings of the Japan Academy, Series B83(8), 266-275.

Noori, N., Drake, J. M., & Rohani, P. (2017). Comparative epidemiology of poliovirus transmission. Scientific reports7(1), 17362.

van den Pol, A. N. (2013). Polio, still lurking in the shadows. Journal of Neuroscience33(3), 855-862.

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