What is Polio?

Polio (also known as Poliomyelitis)

An infectious disease that can be transmitted from person to person. Polio is caused by poliovirus, an enterovirus. Poliovirus is most well known for causing paralysis in young children.[0]

Poliovirus is part of the picornavirus viral family, a taxonomic grouping that includes other familiar viruses such as the rhino virus and hepatitis A virus. These viruses are most known for their icosahedral capsid(20 faces) structure that lacks a viral envelope and carries the positive-sense single stranded RNA genome. Further characteristics include being able to withstand low pH and thus able to pass through the stomach to infect and replicate in the intestinal epithelial cells and being incredibly infectious through the fecal-oral route. [0]

*funfact: Humans are the only natural hosts of this disease. Chimapanzees, Green African Monkeys etc can only be experimentally infected.

Whilst most infections are asymptomatic, viral particles that gain entrance into the central nervous system can replicate in neurons and destroy cells that govern muscle function resulting in flaccid paralysis.[0] To simply put it, the poliovirus invades the brain and spinal cord and may cause paralysis. However, 72 out of 100 infected people will not have any visible symptoms.[1]

Symptoms commonly include:
-Sore throat
-Fever
-Feeling lethargic
-Nausea
-Headache
-Stomach pains

More severe symptoms include:
-Paresthesia ( pins and needles in arms and legs or both)
-Meningitis (Inflammation of the brain & spinal cord)
-Paralysis or weakness of arms and legs

*Paralysis may be fatal due to the inactivation of muscles that aid in respiration. Hence Polio is often referred as a paralytic infection.

Poliovirus is easily transmitted through contact with an infected person. The virus lives in the infected person's throat and intestine. It enters the body though contact of feces and though less common, sneezes and coughs. Contamination of everyday items after not properly washing after using the toilet may speed up the infection rate. This is especially so in rural countries living in unsanitary conditions.

*The poliovirus may be cured with Oral Poliovirus Vaccine(OPV) or Inactivated Poliovirus Vaccine(IPV) but there are cases of Post-polio syndrome where patients recover after a vaccination but there happened to be a relapse of the patient's previous condition. [1]

Reference:
[0]Poliomyelitis. (n.d.). Retrieved July 31, 2015, from https://microbewiki.kenyon.edu/index.php/Poliomyelitis
[1] What Is Polio? (2014, October 15). Retrieved July 31, 2015, from http://www.cdc.gov/polio/about/

Cameroon Case (Part I)

21 November 2013 - A wild poliovirus type 1 was confirmed in Cameroon. The first reported case of poliovirus was in the 2009.  The Wild poliovirus was isolated from 2 acute flaccid paralysis(AFP) cases from the west region with the onset of paralysis on 1 October and 19 October 2013. Genetic sequencing of the virus indicates a possible link between the Cameroon poliovirus and the wild poliovirus detected in Chad in 2011.

Measures for an emergency outbreak response was implemented with at least 3 national immunization days (NIDs) that was conducted on 25-27 October 2013. Subnational immunization days in December followed by 2 subsequent NIDs in January and Febuary 2014. Routine immunization rates were approximately 85.3% for Oral Polio Vaccine (OPV3). Response from neighboring countries Chad and Central African Republic was also drafted.

As the strain was last detected in 2011 in Chad, plans to develop and strengthen sub-national surveillance sensitivity and activities with detailed analysis across the region was drafted to more ascertain any gaps.

In 2013, the far north region of Cameroon also reported 4 cases of circulated Vaccince Derived Poliovirus type 2 (cVDPV2). Patients developed paralysis between 9 May and 12 August 2013. Again, from genetic sequencing, it was discovered that the viruses were linked to a circulation in Chad which was also detected in Nigeria and Niger. Several large-scale supplementary immunization activities were then conducted during the months of August and September followed by NIDs subsequently in October 2013.

This confirms the risk of ongoing international spread of pathogens due to globalization. Who had reflected and assessed the risk of further international spread across the region based on the history of international spread of polio from Northern Nigeria across the West and Central Africa and subnational surveillance gaps and labelled the risk as HIGH. [7]

Reference:
[7] Wild poliovirus in Cameroon. (2013, November 1). Retrieved June 20, 2015, from http://www.who.int/csr/don/2013_11_21/en/
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