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/

2014 South Sudan and Madagscar Updates

Although Nigeria, Paskistan and Afghanistan are the primary 3 countries with cVDPVs, the Poliovirus has been spotted outside these 3 countries as well..

14 November 2014

Separate cases of a circulating cVDPVs was confirmed in South Sudan and Madagascar. 

In South Sudan, 2 cases of type 2 cVDPV cases was confirmed with strains isolated from 2 acute flacid paralysis(AFP) cases in Unity State with the onset of paralysis on 9 September and 12 September 2014 respectively. The cause was later discovered that almost 33% of the children in Unity State are under-immunized against Poliovirus. The two patients were found to be from an internally-displaced persons camp due to civil unrest in Unity State which led to displacement and decline in immunization. Other than the Civil unrest, South Sudan was also participating in the Horn of Africa outbreak response which led them to be exposed to the ongoing wild type 1 poliovirus that was affecting that region. 

In response to the posing threat from the Horn of Africa response, South Sudan had conducted 2 National Immunization Days on April and May for trivalent and bivalent Oral Polio vaccines respectively. Upon receiving the confirmation of the 2 cVDPVs, another series of National Immunization Day was conducted on the 4 November 2014 with trivalent OPV, a subnational immunization day with states with civil unrest on 2 December 2014 and January 2015 with trivalent OPV. The series of immunization done was aimed at containing the spread of the disease by further boosting the community against type 1 polio and the risk of a re-infection from parts of the Horn of Africa.

In Madagascar, cVDPV type 1 was detected after the virus was isolated from a case of AFP with the onset of paralysis of the patient on 29 September 2014 and 3 healthy contacts. In response to this, Madagascar also conducted National Immunization Days in January 2015. The last documentation of a National Immunization Day for Madagascar was in December 2011/January 2012. This led to a highly under-immunized community . A cVDPV outbreak had affected Madagascar before in the years 2001/2002 and 2005. Rapid Concerted outbreak responses stopped those events from continuing but repeated emergence of separate cVDPV activities may increase the risk of such diseases occurring in populations not fully immunized against the poliovirus. Hence, stresses the importance of maintaining high levels of vaccination coverage.

WHO Risk Assessment: 
WHO states that circulating VDPVs are rare but there are instances of well documented strains in populations under-immunized. With the low risk of VDPVs, use of OPV must be stopped in a phase manner to secure a polio free environment as it was discovered that type 2 component contained trivalent OPV accounts for 90% of all cVDPV cases.

From the background of the reports in Madagascar and South Sudan, WHO deemed the risk of international spread of the cVDPV to be low and advises any travelers to be vaccinated fully against poliovirus before making a trip to previously affected areas in both countries. [12]

Reference:
[12] Poliovirus in South Sudan and Madagascar. (2014, November ). Retrieved June 30, 2015, from http://www.who.int/csr/don/14-november-2014-polio/en/
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