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.

• Fever

  Symptoms are fever, severe headache, stiff neck and back, deep muscle pain, and sometimes areas of hyperesthesia (increased sensation) and paresthesia (altered sensation). [medicinenet.com]

  Guillain-Barré syndrome causes flaccid paralysis but can be distinguished because of the following: It usually causes no fever. Muscle weakness is symmetric. [merckmanuals.com]

  In contrast to GBS, weakness occurs at the height of the fever and generally does not progress after the fever subsides. An asymmetrical, flaccid paralysis develops in most patients, typically affecting proximal more than distal muscles. [archneur.jamanetwork.com]

• Malaise

  Symptoms are slight fever, malaise, headache, sore throat, and vomiting 3-5 days after exposure. Recovery occurs in 24-72 hours. This is termed the abortive type of polio. Polio as a major illness may or may not be paralytic. [medicinenet.com]

  SUBCLINICAL INFECTION SYMPTOMS General discomfort or uneasiness ( malaise ) Headache Red throat Slight fever Sore throat Vomiting People with subclinical polio infection might not have symptoms, or mild symptoms may last 72 hours or less. [nlm.nih.gov]

  Symptomatic disease is classified as Abortive poliomyelitis Paralytic or nonparalytic poliomyelitis Most symptomatic infections, particularly in young children, are minor, with 1 to 3 days of slight fever, malaise, headache, sore throat, and vomiting, [merckmanuals.com]

• Acutely Ill Patient

  DIAGNOSIS The diagnosis is made by identifying poliovirus in clinical specimens (usually stool) obtained from an acutely ill patient. [wwwnc.cdc.gov]

• Difficulty Climbing Stairs

  […] a ] N/A 85%[ a ] Difficulty climbing Stairs N/A 61% 67%[ a ] 82% Difficulty with ADLS 14% 17% 16% 62% a = Most common new problem. [web.archive.org]

• Sleep Apnea

  Common signs and symptoms include: Progressive muscle or joint weakness and pain Fatigue Muscle wasting (atrophy) Breathing or swallowing problems Sleep-related breathing disorders, such as sleep apnea Decreased tolerance of cold temperatures When to [mayoclinic.org]

  […] related breathing problems (sleep apnea) Trouble swallowing Causes Poliomyelitis Polio is caused by the poliovirus, a highly contagious virus specific to humans. [nigeriagalleria.com]

  Common symptoms of post-polio syndrome (PPS) are: continuing muscle and joint weakness muscle pain that gets worse becoming easily exhausted or fatigued muscle wasting, also called muscle atrophy trouble breathing and swallowing sleep apnea, or sleep-related [healthline.com]

• Hoarseness

  […] the neck and along the spine For paralytic poliomyelitis the symptoms of nonparalytic and abortive poliomyelitis muscle weakness all over severe constipation muscle wasting weakened breathing difficulty swallowing weak cough flushed or blotchy skin hoarse [childrenshospital.org]

  Watch for: Difficulty breathing Weakness Hoarseness or wheezing Rapid heart rate Hives Dizziness If you or your child has an allergic reaction after any shot, get medical help immediately. [mayoclinic.org]

  Although most rhinovirus infections manifest as mild common colds with rhinorrhea, nasal obstruction, fever, sore throat, coughs, and hoarseness lasting for a few days, serious lower respiratory tract illnesses in infants are common. [ncbi.nlm.nih.gov]

• Vomiting

  The most common include For abortive poliomyelitis fever (up to 103º F) decreased appetite nausea and/or vomiting sore throat not feeling well constipation abdominal pain For nonparalytic poliomyelitis headache, nausea and vomiting may be worse child [childrenshospital.org]

  Initial symptoms of polio include fever, fatigue, headache, vomiting, stiffness in the neck, and pain in the limbs. In a small proportion of cases, the disease causes paralysis, which is often permanent. [who.int]

  Initial symptoms of polio include fever, fatigue, headache, vomiting, stiffness in the neck, and pain in the limbs. In a small proportion of cases, the disease causes paralysis, which is often permanent. Polio can only be prevented by immunization. [greenfacts.org]

• Nausea

  The most common include For abortive poliomyelitis fever (up to 103º F) decreased appetite nausea and/or vomiting sore throat not feeling well constipation abdominal pain For nonparalytic poliomyelitis headache, nausea and vomiting may be worse child [childrenshospital.org]

  Those who get symptoms at first may experience: fever sore throat headache abdominal pain nausea vomiting tiredness loss of appetite aching muscles stiff neck or back Typically, symptoms last between 2 and 10 days and go away on their own. [canada.ca]

  Symptoms Non-specific symptoms which may also occur with other virus infections are seen in the early stages of the illness: nausea, headaches, fever and possibly diarrhoea. [ottobock-export.com]

  Abortive polio: In these cases, polio is a mild illness, with viral-like symptoms such as fever, fatigue, headache, sore throat, nausea, and diarrhea. [historyofvaccines.org]

• Diarrhea

  The remaining 5% show the typical signs of this disease which include fever, headache, vomiting, diarrhea, neck stiffness and pain in arms and legs. [symptoma.com]

  Some children may have a fever, or experience crankiness, drowsiness, loss of appetite, vomiting, and diarrhea. These reactions are mild and generally last 1 to 2 days. [immunizebc.ca]

  Abortive polio: In these cases, polio is a mild illness, with viral-like symptoms such as fever, fatigue, headache, sore throat, nausea, and diarrhea. [historyofvaccines.org]

  Symptoms Non-specific symptoms, which may also occur with other viral infections, are seen in the early stages of the illness: nausea, headaches, fever and possibly diarrhea. [ottobockus.com]

  The effect of diarrhea on oral poliovirus vaccine failure in Brazil, J Infect Dis, 1997, vol. 175 Suppl 1 (pg. [dx.doi.org]

• Dysphagia

  Clinical features include impaired respiration, HYPERTENSION, alterations of vasomotor control, and dysphagia. Weakness and atrophy of the limbs and trunk due to spinal cord involvement is usually associated. [mesh.kib.ki.se]

  It has been shown that iron deficiency can precede dysphagia [39]. [ncbi.nlm.nih.gov]

• Constipation

  The most common include For abortive poliomyelitis fever (up to 103º F) decreased appetite nausea and/or vomiting sore throat not feeling well constipation abdominal pain For nonparalytic poliomyelitis headache, nausea and vomiting may be worse child [childrenshospital.org]

  Simulates "acute respiratory infection or gastroenteritis... symptoms are fever, headache, vomiting, diarrhea, constipation, and sore throat."1 Nonparalytic Polio. [doi.org]

• Cyanosis

  Cyanosis or blueness of the skin will occur as the tissues lose their oxygen. Decreased levels of consciousness may occur because of the low blood pressure, decreased brain perfusion, and low oxygenation. [emedicinehealth.com]

  […] that usually worsens when taking a deep breath, known as pleuritic pain fast heartbeat fatigue and weakness nausea and vomiting diarrhea sweating headache muscle pain confusion or delirium, especially in older adults dusky or purplish skin color, or cyanosis [medicalnewstoday.com]

  Patients may have symptoms and signs, such as hiccough, shallowness and slowing of respiration, cyanosis, restlessness, and anxiety. [sites.google.com]

  […] stabbing, ipsilateral pleuritic chest pain and dyspnea Reduced, or absent breath sounds, hyperresonant percussion, decreased fremitus on the ipsilateral side Subcutaneous emphysema Additionally in tension pneumothorax: Severe acute respiratory distress: cyanosis [amboss.com]

  Other symptoms may include: a steady ache in the chest shortness of breath, or dyspnea breaking out in a cold sweat tightness in the chest turning blue, or cyanosis severe tachycardia, or a fast heart rate The risk factors are different for a traumatic [healthline.com]

• Muscle Weakness

  Muscle weakness may be responsible for postoperative instability, and careful selection of the patient with good upper extremity muscles must be made. Copyright © 2016 Journal of Shoulder and Elbow Surgery Board of Trustees. [ncbi.nlm.nih.gov]

  "In addition to symptoms of nonparalytic poliomyelitis, tremors and muscle weakness appear.... [doi.org]

  About four to five percent of infected people have minor symptoms such as fever, muscle weakness, headache, nausea and vomiting. One to two percent of infected persons develop severe muscle pain and stiffness in the neck and back. [health.ny.gov]

• Muscular Atrophy

  We report the case of PPS in a patient, 40 years, that thirty-five years after had had paralytic poliomyelitis, developed new symptoms of fatigue, muscular atrophy, dyspnea, difficulties in deambulation and muscular and joint pain. [ncbi.nlm.nih.gov]

  atrophy Increasing joint instability/joint deformities Cramping Subsultus (fasciculation) Changes in gait pattern and/or an increased tendency to fall Therapy Since no causative antiviral therapy exists, treatment is limited to symptomatic measures. [ottobock-export.com]

• Myalgia

  In paralytic poliomyelitis, muscle weakness is preceded by intense myalgias of the involved limbs and axial skeleton. [medlink.com]

  Most children with polio exhibit paralysis of just one leg, which may have begun weeks earlier during a cold or gastroenteritis along with symptoms such as fever, headache, sore throat, and myalgia. [web.archive.org]

  GBS, the fever, short latent period, and CSF pleocytosis suggested an acute infectious process, and with the MRI findings were characteristic of poliomyelitis. 3, 5, 7 - 12 The prodrome of paralytic poliomyelitis consists of malaise, headache, fever, myalgias [archneur.jamanetwork.com]

• Muscle Tenderness

  Before one week signs & symptoms explicit to paralytic polio surfaces and they include: • Reflex loss • Relentless muscle tenderness/ weakness • Loose and flaccid limbs Causes The history of the fight against this disease The polio virus exists in only [wikisickness.com]

  Symptoms/Signs of Nonparalytic Poliomyelitis Arm and leg pain or stiffness Abnormal reflexes Back and neck pain and stiffness, Fatigue Fever Headache Muscle tenderness and spasms Problems swallowing and/or breathing Sore throat in the absence of upper [nigeriagalleria.com]

  Non-paralytic poliomyelitis [ ✎ edit | edit source ] Symptoms include back pain or backache, diarrhea, excessive tiredness, fatigue, headache, irritability, leg pain (calf muscles), moderate fever, muscle stiffness, muscle tenderness and spasm in any [wikilectures.eu]

  These include: fever sore throat headache vomiting fatigue back and neck pain arm and leg stiffness muscle tenderness and spasms meningitis, an infection of the membranes surrounding the brain Paralytic polio symptoms Paralytic polio affects only a small [medicalnewstoday.com]

• Back Pain

  They complain of increasing muscle weakness, joint and muscle pain, fatigue, breathing difficulties, loss of stamina, low back pain, and intolerance to cold. In at least 1 out of 25 survivors, the symptoms are disabling. [questia.com]

  The symptoms of nonparalytic infections are: back pain diarrhea fatigue irritability headache leg pain moderate fewer muscle stiffness neck pain stiffness of the arms skin rush vomiting Less than 1% of patients end up with the paralytic symptoms which [lifesafe.wordpress.com]

  Signs and symptoms, which can last up to 10 days, include: Fever Sore throat Headache Vomiting Fatigue Back pain or stiffness Neck pain or stiffness Pain or stiffness in the arms or legs Muscle weakness or tenderness Paralytic polio This most serious [mayoclinic.org]

  […] area of the body, neck pain and stiffness, pain in front part of neck, pain or stiffness of the back, arms, legs, abdomen, skin rash or lesion with pain, vomiting. [wikilectures.eu]

• Urinary Retention

  Initial urinary retention is common. Gastrointestinal disturbances (nausea, vomiting, diarrhoea), muscle pain and meningeal symptoms may also occur. Look for the polio virus in stool samples. [medicalguidelines.msf.org]

  Common manifestations of paralytic poliomyelitis in addition to aseptic meningitis include deep muscle pain, hyperesthesias, paresthesias, and, during active myelitis, urinary retention and muscle spasms. [merckmanuals.com]

  retention. v Stiffness and pain in the neck and back because of meningeal irritation, as well as abnormalities of autonomic function, also can be seen in some patients. v Cranial nerve involvement o Approximately 10-15% of cases affect the lower brainstem [sites.google.com]

  retention, sensory symptoms and signs, autonomic dysfunction (including hyperhidrosis or hypohidrosis), and decreased limb temperature may occur Recovery stage In the recovery stage, also known as the convalescent stage, the acute symptoms and muscle [emedicine.medscape.com]

• Urinary Incontinence

  Neurologic examination confirmed spastic triparesis, urinary incontinence, diminution of tactile sensation, and vision deterioration. Hemography, serum laboratory findings, and urinalysis were normal. [ncbi.nlm.nih.gov]

• Headache

  Symptoms are fever, severe headache, stiff neck and back, deep muscle pain, and sometimes areas of hyperesthesia (increased sensation) and paresthesia (altered sensation). [medicinenet.com]

  Patients with fever, headache, stiff neck, and mild muscle spasms often were not reported or hospitalized. [doi.org]

  Symptoms of i nfection: The symptoms of subclinical infections are: general discomfort headache red throat sore throat vomiting slight fewer Up to 95% of patients with subclinical polio infections may not show the symptoms or they may last 72 hours or [lifesafe.wordpress.com]

• Flaccid Paralysis

  The objective of this paper was to review the need for acute flaccid paralysis surveillance by presenting two cases. [ncbi.nlm.nih.gov]

  Asymmetric flaccid paralysis may develop and progress over 2 to 3 days. Encephalitic signs occasionally predominate. [merckmanuals.com]

• Meningism

  […] non-septic meningitis, followed by a few days of being symptoms free then paralysis develops lower limbs more often affected than upper limbs Plain radiograph and CT With acute infection, no radiographic features are typically evident. [radiopaedia.org]

  About 4% of patients with poliovirus infection develop nonparalytic central nervous system involvement with aseptic meningitis. [merckmanuals.com]

  (See the Meningitis Research Foundation website for more detailed information on the signs and symptoms of meningitis.) How is it passed on? Polio is caused by infection with one of three types of virus. [vk.ovg.ox.ac.uk]

  Related: Cholera on the Horn of Africa Niger meningitis outbreak: MSF teams have vaccinated more than 358,800 people Meningitis established as cause of Liberia cluster Nigeria meningitis outbreak climbs past 14,000 cases, situation improving Malaria outbreak [outbreaknewstoday.com]

• Stroke

  Blood clots also may form in the heart, leading to a stroke or heart attack. Cor pulmonale. [web.archive.org]

  Disease Control and Prevention Start Here Polio (Mayo Foundation for Medical Education and Research) Also in Spanish Polio Vaccination (Centers for Disease Control and Prevention) Post-Polio Syndrome (National Institute of Neurological Disorders and Stroke [medlineplus.gov]

  ^ a b c "Post-Polio Syndrome Fact Sheet: National Institute of Neurological Disorders and Stroke (NINDS)". Archived from the original on 29 July 2011. Retrieved 30 December 2008. ^ a b c Jubelt B, Agre JC (July 2000). [en.wikipedia.org]

  […] can get pneumonia, but those most at risk for the lung infection are children under age 5, adults 65 and over, cigarette smokers and people with other health problems or weak immune systems, such as chronic lung problems, heart failure, diabetes and stroke [livescience.com]

• Guillain-Barré Syndrome

  The most severe cases of Guillain-Barré Syndrome often have persistent objective sensory loss, associated with greater weakness in the feet and hands, which show no resemblance to FDR's impairment and disability. [ncbi.nlm.nih.gov]

  The Guillain–Barré syndrome. New England Journal of Medicine 1992 ; 326: 1130 – 1136. Google Scholar | Crossref | Medline | ISI 12. Hughes, RA, Rees, JH. Clinical and epidemiologic features of Guillain–Barré syndrome. [doi.org]

  Ropper AHWijdicks EFMTruax BT Guillain-Barré Syndrome. Philadelphia, Pa: FA Davis Co Publishers; 1991. 5. Yohannan MDRamia SAl Frayh ARS Acute paralytic poliomyelitis presenting as Guillain-Barré syndrome. J Infect. 1991;22:129-133. [archneur.jamanetwork.com]

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].

• Hypercapnia

  A similar finding of central involvement of respiration was noted by Plum, who also stressed the importance of hypercapnia. Plum emphasized measurements of vital capacity and techniques to minimize trauma with suctioning after tracheostomy. [ncbi.nlm.nih.gov]

  When not corrected, insidiously progressive hypercapnia leads to a compensatory metabolic alkalosis. [web.archive.org]

• Leukocytosis

  Order a complete blood count (CBC), because leukocytosis may be present. Perform virus recovery from throat washing, stool culture, blood culture, and CSF culture. Viral studies in stool specimens are essential for the diagnosis of poliomyelitis. [sites.google.com]

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.