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Monday, January 19, 2015

India Within WHO Certified Polio Free Region

Verdict :
Possible time of origin : March 2014

Circulation platforms : Internet

Circulation geography : Global

Original Message Version Under Analysis:
Polio-free certification: WHO South-East Asia
The WHO South-East Asia Region has been maintaining its polio-free status for the last 3 years. After the last wild polio case was reported from India on 13 January 2011, the Region is firmly on track for polio-free certification in March 2014.
In order to ensure all the requirements for certification of polio eradication are met by the Member States, a review of the annual updates of respective national documentation including phase-1 laboratory containment reports will be conducted during the 7th meeting of the SEA-RCCPE. This review will take place in the WHO Regional Office in New Delhi, India on 26-27 March 2014.
A formal process for the certification of global polio eradication was set up based on the experience gained during smallpox eradication. In 1995, the WHO Director-General established the Global Certification Commission for Polio Eradication. The respective Regional Commission came to life in 1997 and national certification committees for polio eradication of the 11 countries in the Region were established by the end of 1998. As no single country can be certified as polio-free; a WHO Region is certified as a whole after all its countries sustain no new transmissions for 3 years.
Analysis by Merofact Awareness Team:
Rukhsar Khatoon has the last case of polio detected on January 13, 2011 in India, pictured here with her mother Shabida Bibi in Shahapar village, West Bengal, India.
Credit: Adapted from image uploaded by Gates Foundation under Creative Commons License. 

This new year I would like to continue blogging with the news above on a global health success achieved last year. It's obviously a reason to be proud of. But before we show complacency and start forgetting polio like small pox, let's dive into few less publicized knowledge and facts. 
As the acclaimed news says South-East Asia including is polio free and the last known case of Polio or Acute Flaccid Paralysis (AFP) in the region was in West Bengal, India. Now, we know that West Bengal is nearly ~2000 km away from Rajasthan, which is just ~500 km apart from still polio endemic region in Pakistan. Find India in the map below and look at the proximity of the red patches describing polio occurrence in 2014.
Before discussing any other issues, we need to look at the history of polio and its vaccine. Polio is an infectious viral disease and the causal virus multiplies in the throat and intestinal tract of the host. It may spread through person-to-person contact or with the stool of an infected person and may also be spread through oral/nasal secretions. Centers for Disease Control and Prevention, USA (CDC) explains that "Most people infected with the polio virus have no symptoms; however, for the less than 1% who develop paralysis it may result in permanent disability and even death."
With the discovery of polio vaccine it was realized that polio is preventable. The first polio vaccine was developed and tested by Jonas Salk in 1952, which was a injectible Inactivated (i.e. dead) Poliovirus Vaccine (IPV). 5 years later Albert Sabine developed a Oral Poliovirus Vaccine (OPV) where attenuated (living) polio virus was used. Together these two vaccines (IPV and OPV) have eradicated polio from most parts of the world, and reduced the worldwide incidence from an estimated ~350,000 cases in 1988 to just 407 reported cases in 2013 (as of April 29, 2014).
The Salk vaccine or IPV contains dead form of three wild, virulent reference strains, Mahoney (type 1 poliovirus), MEF-1 (type 2 poliovirus), and Saukett (type 3 poliovirus). These polio virus strains are grown in animal cell culture and then inactivated/killed using formalin. The injected IPV induces IgG mediated humoral immunity in the subject. On the other hand, Sabine oral polio vaccine (OPV) contains a mixture of all three or fewer types of reference live attenuated poliovirus. In this case wild type poliovirus reference strains are cultured by the passage through non-human cells at a sub-optimal temperature, which induces spontaneous mutations in the viral genome leading to reduced virulence or attenuation. The attenuated poliovirus in the Sabin vaccine replicates very efficiently in the gut, the primary site of infection and replication of the wild type, but is unable to replicate efficiently within  nervous system tissue.
OPV turned out to be superior than IPV in terms of mode of administration, specially for babies, eliminating the need for sterile syringes and making the vaccine more suitable for mass vaccination campaigns. But a major concern about the OPV is its known ability to revert back to a form that can regain virulence and achieve neurological infection and cause paralysis. Keeping this in mind, OPV has not been used in the United States since 2000 but is still used in many parts of the world, while more and more developed countries stopped using OPV and totally switched to IPV.
  Interested readers may find the following links useful:

CDC: Morbidity and Mortality Weekly Report
Polio Eradication and Endgame Strategic Plan 2013-2018
Inactivated polio vaccine: time to introduce it in India's national immunization schedule
Ending polio, one type at a time
Eradicating poliomyelitis: India's journey from hyperendemic to polio-free status
Neurovirulence of Type 1 Polioviruses Isolated from Sewage in Japan
The Hindu: The Politics of Polio
The Hindu: Polio Free Does Not Mean Paralysis Free

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