Poliomyelitis

Poliomyelitis shows a wide range of possible clinical scenarios. In the majority of them (around 95%), the disease is asymptomatic or shows flu-like symptoms which do not represent a major concern for the patient. The remaining 5% of the cases are divided in two major groups: non-paralytic poliomyelitis, representing 4% of the cases, and paralytic poliomyelitis, representing around 1% of the cases. The non-paralytic form shows the usual flu-like symptoms plus aseptic meningitis. The paralytic type, instead, shows a series of other clinical manifestations which follow a gradual progression. At the beginning, the disease appears as a flu-like illness whose symptoms subside within a few days. Then, an asymmetrical, flaccid motor paralysis begins to appear, which mainly affects the lower limbs and peaks after 48 hours. In about 10-25% of the cases this second stage might progress into a third one, represented by a bulbar form of paralysis. The classical symptoms of this third stage include hyper- or hypotension, respiratory failure, dysphagia and dysphonia. In rare cases, the penetration of the central neuron system might be so severe that acute encephalitis can occur.

Physical examination of the subjects affected might show acute onset of flaccid paralysis in one or more limbs. Furthermore, the limbs affected appear to have decreased or absent tendon reflexes not related to another etiological factor, with no sensory or cognitive loss associated [25].

Laboratory studies reveal the presence of poliovirus, especially in the blood, very early during the course of the infection [2]. Moreover, by performing a lumbar puncture it is possible to reveal high concentrations of white blood cells and slightly elevated protein levels in the cerebrospinal fluid of the patient. PCR is also frequently used as diagnostic test, as it can allow to distinguish the wild type of poliovirus, which is usually found in nature, from the vaccine type, coming from a strain developed to produce vaccine [26].

There is no treatment of poliomyelitis, apart for the treatment of minor pathological conditions like paralysis and respiratory complications whose aim is to prevent or limit disease progression.

The gastrointestinal complications are usually treated through oral rehydration and/or fluids administered intravenously to prevent volume depletion. Unfortunately, paralytic poliomyelitis too has no treatment, and the limb affected is simply immobilized early to perform physical therapy and minimize handicaps [24] [27] [28] [29]. Limb paralysis might progress into respiratory paralysis, a dangerous and life-threatening stage which requires supportive measures including incubation and ventilation [30].

There might be another poliomyelitis-related syndrome that usually manifests itself many years after the appearance of paralytic poliomyelitis, known as postpoliomyelitis syndrome. This pathological condition consists if fatigue, weakness and wasting of the affected limbs that requires immobilization and physical therapy [31] [32] [33].

It is important to notify any case of poliomyelitis to the local health authorities when it appears.

The prognosis of poliomyelitis is generally good. The milder types of poliovirus infections are asymptomatic and carry no specific complication, while in the cases of paralytic poliomyelitis muscle function gradually returns back to normal with no residual paralysis for most of the time. Rare instead, are the cases of death, which occur much more frequently in adults than children usually as bulbar poliomyelitis. If death comes, this generally occurs within 2 weeks from infection.

Poliomyelitis is caused by poliovirus, an enterovirus belonging to the family Picornaviridae. This is a classical RNA virus, made up of a RNA genome of around 7500 nucleotides [10] protected and enveloped by a protein capsid [11]. The virus mainly attacks the gastrointestinal tract [12] especially the oropharynx and intestine, with an incubation time ranging from 3 to 35 days. So far, three serotypes have been identified, type 1, type 2, and type 3. Type 1 is the most common of these three and certainly the one closely associated with muscle weakness and paralysis [13].

Poliomyelitis is mainly transmitted via fecal-oral route [14], especially in poor regions, but in areas with good hygienic conditions it can occasionally spread via oral-oral route [13]. The disease has a seasonal transmission trend, with a peak during summer and winter, and appears to affect only human beings.

Poliomyelitis has been eradicated in the western world since 1991 [15], apart from some travel-related cases which occurred in the US [16] over the last few years. The other countries can be divided in two major groups: the ones where the disorder is endemic and the ones where it is sporadic. 131 new cases were reported in 2012, 115 of which occurred in endemic countries and 16 in non-endemic ones [17]. Endemic regions include countries like Afghanistan, Pakistan, and Nigeria, while non-endemic ones include countries like Somalia, Equatorial Guinea, Cameron, and Iraq. The majority of these countries are in the tropical region, with a peak of transmission at the end of summer perhaps due to the confluence of hot temperatures and rainy conditions. Unfortunately, the vast majority of these cases is represented by children less than 36 months of age. There is no epidemiological difference in the epidemiology between females and males [18] [19].

Poliovirus enters the body through the mouth, where it begins to move towards the gastrointestinal system. From here, it spreads to the tonsils, the intestinal lymphoid tissue and the deep cervical and mesenteric lymph nodes, where the virus finds the perfect conditions to multiply. Poliovirus then returns to the bloodstream and the other sites of the body [20], such as brown fat, reticuloendothelial tissues, and muscles [21]. The central nervous system [22] is another site sometimes reached by poliovirus, even though experts believe this is just an accidental deviation from the normal intestinal infection, with no relation with the age, gender, and socioeconomic position of the individual affected [23]. Here, poliovirus mainly affect motor neurons in the anterior horn and brainstem, and this is the reason why it causes the development of acute flaccid paralysis [24].

Vaccination is the primary means of prevention [34]. The polio vaccine has proved to be effective in blocking person-to-person transmission and therefore preventing the spread of the infection in large communities. Vaccines should not be given to those who have experienced anaphylactic reaction to a previous dose of IPV-containing vaccines or to neomycin, streptomycin and polymyxin B.

Poliovirus can invade several parts of the human body. It usually firstly affects the lymphatic tissue and enters the blood stream, where it can reach motor neurons causing flaccid paralysis. For this broad action, poliovirus can cause a wide spectrum of possible effects, from asymptomatic to meningitic or paralytic acute illness, many of which can provoke a characteristic permanent muscle weakness. The majority of the cases, from 90% to 95%, have no symptoms [1], while the remaining 5 to 10% are characterized by several signs such as fever, headache, vomiting, diarrhea, neck stiffness and pain in arms and legs [1] [2]. Unfortunately, from 2% to 5% of children and from 15% to 30% of adults who show muscle weakness die.

Poliovirus usually spreads from person to person through infected feces generally found in food, water, or saliva. There is no particular treatment for poliomyelitis, and even though a vaccine has been developed, the disease is still widespread, especially in poor countries such as Afghanistan, Nigeria, and Pakistan, where polio vaccination is highly recommended [3].

With descriptions of its effects present in ancient Egyptian art, poliomyelitis is one of the most ancient diseases known by human beings. The infection was first described at the end of the 18th century, while poliovirus was first identified at the beginning of the 20th century [4]. Although the vaccine was developed in the 1950s [5], the disorder still remains a concerning childhood disease [6], especially in poor regions like Asia, Africa and the Middle East [7]. New cases have been reported in Syria in 2013 [8], but experts hope to globally eradicate the disease by 2018 [9].

Poliomyelitis is the infectious disease caused by poliovirus. This virus can invade many parts of the body, causing a wide range of clinical manifestations. The great majority of the cases, around 95%, show no signs and symptoms, and are therefore called “asymptomatic”. The remaining 5% show the typical signs of this disease which include fever, headache, vomiting, diarrhea, neck stiffness and pain in arms and legs. The condition might degenerate and cause paralysis of the limbs, especially legs, with great negative consequences for the life of the people affected.

The infection is still widespread in poor countries, especially the tropical ones, where the cases of death number around several hundred each year. In the western world the disease has been totally eradicated, apart from some travel-related cases of people who got the infection abroad.

There is no treatment for poliomyelitis, and prevention is only possible through vaccination.

1. Atkinson W, Hamborsky J, McIntyre L, Wolfe S (eds.). Poliomyelitis. Epidemiology and Prevention of Vaccine-Preventable Diseases. The Pink Book 2009 (11th ed.). Washington DC: Public Health Foundation. pp. 231–44. 
2. WHO. Poliomyelitis Fact sheet N°114. October 2014. 
3. Centers for Disease Control and Prevention (CDC). Guidance to US Clinicians Regarding New WHO Polio Vaccination Requirements for Travel by Residents of and Long-term Visitors to Countries with Active Polio Transmission. June 2, 2014. 
4. Daniel, edited by Thomas M, Robbins, Frederick C. Polio (1st ed. ed.). Rochester, N.Y.: University of Rochester Press. p. 11. 1999
5. Aylward R. Eradicating polio: today's challenges and tomorrow's legacy. Ann Trop Med Parasitol 2006 100 (5–6): 401–13. 
6. Wheeler, Derek S, Wong, Hector R, (eds.), Shanley TP. Science and practice of pediatric critical care medicine. London: Springer. pp. 10–11. 2009
7. WHO. WHO statement on the meeting of the International Health Regulations Emergency Committee concerning the international spread of wild poliovirus. 5 May 2014. 
8. WHO. Polio in the Syrian Arab Republic - update. 26 November 2013. 
9. WHO. Global leaders support new six-year plan to deliver a polio-free world by 2018. 25 April 2013. 
10. Hogle J. Poliovirus cell entry: common structural themes in viral cell entry pathways. Annu Rev Microbiol 2002 56: 677–702. 
11. Ryan KJ, Ray CG (eds.). Enteroviruses. Sherris Medical Microbiology (4th ed.). McGraw Hill. pp. 535–7. 2004
12. Cohen JI. Enteroviruses and Reoviruses. In: Kasper DL, Braunwald E, Fauci AS, et al. (eds.). Harrison's Principles of Internal Medicine (16th ed.). McGraw-Hill Professional; 2004. p. 1144.
13. Linda K Ohri, Jonathan G. Marquess. Polio: Will We Soon Vanquish an Old Enemy?. Drug Benefit Trends 1999 11 (6): 41–54. 
14. Kew O, Sutter R, de Gourville E, Dowdle W, Pallansch M. Vaccine-derived polioviruses and the endgame strategy for global polio eradication. Annu Rev Microbiol 2005 59: 587–635. 
15. Centers for Disease Control and Prevention (CDC). International notes certification of poliomyelitis eradication - the Americas, 1994. MMWR Morb Mortal Wkly Rep. 1994;43:720-722. 
16. Centers for Disease Control and Prevention (CDC). Poliovirus infections in four unvaccinated children-Minnesota, August-October 2005. MMWR Morb Mortal Wkly Rep. 2005;54:1053-1055. 
17. World Health Organization, Global Polio Eradication Initiative. Polio this week. October 2014. http://www.polioeradication.org 
18. Lahariya C, Pradhan SK. Prospects of eradicating poliomyelitis by 2007: compulsory vaccination may be a strategy. Indian J Pediatr. 2007;74:61-63. 
19. American Academy of Pediatrics. Poliovirus infections. In: Pickering LK, Baker CJ, Kimberlin DW, et al, eds. Red Book: 2009. Report of the Committee on Infectious Diseases. 28th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2009:541-545. 
20. Yin-Murphy M, Almond JW. Picornaviruses: The Enteroviruses: Polioviruses. Baron's Medical Microbiology (Baron S et al., eds.) (4th ed.). 1996 Univ of Texas Medical Branch. 
21. Sabin A. Pathogenesis of poliomyelitis; reappraisal in the light of new data. Science 1956 123 (3209): 1151–7. 
22. Chamberlin SL, Narins B (eds.). The Gale Encyclopedia of Neurological Disorders. Detroit: Thomson Gale. pp. 1859–70. 2005
23. Mueller S, Wimmer E, Cello J. Poliovirus and poliomyelitis: a tale of guts, brains, and an accidental event. Virus Res 2005 111 (2): 175–93. 
24. Heymann DL, Aylward RB. Eradicating polio. N Engl J Med. 2004;351:1275-1277. 
25. Centers for Disease Control and Prevention (CDC). Case definitions for infectious conditions under public health surveillance. Morbidity and mortality weekly report 46 (RR–10): 26–7. 1997. 
26. Chezzi C. Rapid diagnosis of poliovirus infection by PCR amplification. J Clin Microbiol 1996 34 (7): 1722–5. 
27. Cochi SL, Kew O. Polio today: are we on the verge of global eradication? JAMA. 2008;300:839-841.
28. Khan OA. Polio and post-polio syndrome. In: Zhang Y, ed. Encyclopedia of global health. Thousand Oaks, CA: Sage; 2008.
29. Neumann DA. Polio: its impact on the people of the United States and the emerging profession of physical therapy. J Orthop Sports Phys Ther. 2004;34:479-492. 
30. Miller AH, Buck LS. Tracheotomy in bulbar poliomyelitis. Calif Med. 1950;72:34-36. 
31. Ramaraj R. Post-poliomyelitis syndrome: clinical features and management. Br J Hosp Med. 2007;68:648-650.
32. Bruno RL. Post-polio syndrome. Neurology. 1996;47:1359-1360. 
33. Farbu E, Gilhus NE, Barnes MP, et al. Post-polio syndrome: EFNS guidelines on post-polio syndrome. In: Gilhus NE, Barnes MP, Brainin M, eds. European Handbook of Neurological Management, Volume 1. 2nd ed. West Sussex, UK: Blackwell Publishing Ltd.; 2011:311-319. 
34. Rinaldo C. Passive Immunization Against Poliomyelitis: The Hammon Gamma Globulin Field Trials, 1951–1953. Am J Public Health 2005 95 (5): 790–9.

• Children of polio victims.
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