Introduction
Overview
Poliovirus is an acute enteroviral infection that is spread from person to person, primarily via the fecal-hand-oral routes. Although most patients who acquire the infection are asymptomatic, those afflicted may develop a variety of neurologic manifestations, including aseptic meningitis, polioencephalitis, bulbar poliomyelitis, and paralytic poliomyelitis. In paralytic poliomyelitis, muscle weakness is preceded by intense myalgias of the involved limbs and axial skeleton. Following recovery, as many as 20% to 30% of individuals who develop paralytic poliomyelitis may suffer from post-polio syndrome, which produces muscle weakness, pain, atrophy, and fatigue many years after acute illness.
There has been a large worldwide effort for poliomyelitis eradication. Polio cases have decreased by over 99% since 1988, from an estimated 350,000 cases in more than 125 endemic countries to 42 reported cases in 2016 (37 wild-type and 5 vaccine-derived) (74; 81; 156; 157; 169; 84; 102). Poliomyelitis due to wild-type virus has now been eliminated from the Americas, Europe, and Western Pacific, and cases in Africa and Asia have markedly decreased. Although great strides have been made, poliomyelitis remains and is rising in some regions, including Nigeria, Afghanistan, and Pakistan, and there is a risk for new outbreaks to occur.
Key points
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• Poliovirus is an acute enteroviral infection that is spread from person to person, primarily via the fecal-hand-oral route. |
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• Neurologic manifestations of poliomyelitis include aseptic meningitis, polioencephalitis, bulbar poliomyelitis, and paralytic poliomyelitis. |
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• As many as 20% to 30% of individuals who develop paralytic poliomyelitis may suffer from post-polio syndrome, which includes new muscle weakness, pain, atrophy, and fatigue many years after the acute illness. |
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• There has been a large worldwide effort for poliomyelitis eradication, with a decrease of polio cases by over 99% since 1988. Though great strides have been made, there remains a high risk for new outbreaks. |
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• On September 20, 2015, the Global Commission for the Certification of Poliomyelitis Eradication declared that poliovirus type 2 has been eradicated worldwide. |
Historical note and terminology
Poliomyelitis has afflicted humans for centuries. The first recognized clinical description was by English physician and surgeon Michael Underwood (1736-1820) in the second edition of A Treatise on Diseases of Children, which was published in 1789 (235; 141; 186). Major contributions to the understanding of the disease were made by the German orthopedist Jacob Heine (1800-1879), who described the clinical features of acute poliomyelitis (96). In 1870, French neurologist Jean-Martin Charcot (1825-1893) and his junior colleague Alix Joffroy (1844-1908) recognized that the flaccid paralysis of poliomyelitis was caused by spinal anterior horn cell damage (49).
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Jacob Heine (1800-1879)
Shown around 1870, Heine was the first to provide a clinical description of poliomyelitis in 1840. (Contributed by Dr. Douglas Lanska. Public domain.)
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Jean-Martin Charcot (1825-1893)
French neurologist Jean-Martin Charcot (1825-1893), who, with colleague Alix Jaffoy, recognized that the flaccid paralysis of poliomyelitis was caused by spinal anterior horn cell damage. (Contributed by Dr. Douglas Lanska. Courte...
In the mid- to late 19th century, the general belief was that polio was not infectious; in the late 19th century, when bacteriological explanations were in vogue for almost all conditions, polio was suspected to be another bacterial disease. Numerous attempts were made to identify the responsible microorganism, with many claims to have successfully done so, but none were reproducible.
Finally, in 1908, Austrian pathologist Karl Landsteiner (1868-1943) and his colleague Erwin Popper (1879-1955) showed that the etiological agent of poliomyelitis was a filterable virus (127). The existence of more than one type of poliovirus was first inferred by Australian virologist Frank Macfarlane Burnet (1899-1984) and his collaborator Dame Annie Jean Macnamara (1899-1968) in 1931 when they demonstrated that monkeys who had recovered from infection with a strain recovered in Melbourne subsequently developed disease when given a virulent mixed virus strain (40; 70). In 1949, the three antigenic poliovirus types (poliovirus 1, poliovirus 2, poliovirus 3) were identified (34; 119).
Sir Frank Macfarlane Burnet (1899-1984)
Australian virologist Sir Frank Macfarlane Burnet (1899-1984) recognized the existence of more than 1 type of poliovirus in 1931. Burnet won the Nobel Prize in Physiology of Medicine in 1961 for predicting acquired immune toleranc...
The first recorded outbreaks of poliomyelitis occurred in the mid- and late nineteenth century in northern Europe and North America, followed by much larger epidemics in the early 20th century.
In August 1921, while vacationing with his family at their summer home on Campobello Island off the coast of Maine, politician Franklin Delano Roosevelt (FDR; 1882-1945) became ill, lost motor power in his legs, and was diagnosed with polio. Roosevelt later sought treatment at a resort in Warm Springs, Georgia. Because of his self-perceived improvement at the resort, in 1927, Roosevelt and his friend, American lawyer Basil O’Connor, created the Georgia Warm Springs Foundation, in which O'Connor served first as treasurer and later as president. The foundation was subsequently reconstituted as the National Foundation for Infantile Paralysis in 1938. A solicitation prior to Roosevelt’s birthday in 1938 resulted in a huge influx of small donations that swamped the White House mail room. As a result, radio star Eddie Cantor dubbed it the “March of Dimes” -- a play on the contemporary radio and newsreel series, The March of Time. The March of Dimes ultimately became the official name of the organization, which served as the largest source of funding for research and clinical care for poliomyelitis at the time. Indeed, the organization supported the work of Jonas Salk and others, which led to the development and testing of polio vaccines.
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Basil O’Connor (1892-1972)
O’Connor was Chairman of the National Foundation for Infantile Paralysis that funded the development and testing of polio vaccines, including the Salk killed virus vaccine. He was also later Chairman and President of the Americ...
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Franklin Delano Roosevelt (1882-1945) and Basil O’Connor (1892-1972)
President Franklin Delano Roosevelt (1882-1945) and Basil O’Connor (1892-1972), chairman of the March of Dimes, counting dimes sent as donations for research and clinical care of people with poliomyelitis (c1944). (Contributed by ...
Prototype “iron lung” negative-pressure ventilators were developed in the late 1920s and early 1930s by industrial hygienist Philip A Drinker (1894-1972), physiology instructor Louis Agassiz Shaw Jr. (1886-1940), and inventor/medical-equipment manufacturer John Haven (“Jack”) Emerson (1908-1997). From around 1926 to 1928, Drinker and Shaw, both at Harvard Medical School in Boston, designed an electrically powered tank respirator. On October 13, 1928, Drinker and pediatrician Charles F McKhann demonstrated the potential of this device in an 8-year-old girl with poliomyelitis, respiratory failure, and coma who was treated at Boston Children’s Hospital and briefly survived before succumbing to pneumonia. A second trial on Friday, September 13, 1929, at Peter Bent Brigham Hospital in Boston, on a 21-year-old Harvard student, was unquestionably successful: Hoyt was weaned from the respirator in 4 weeks and was discharged from the hospital before Christmas. Emerson built a mechanically superior device in the summer of 1931; Emerson’s device was first used clinically to save the life of a priest with polio at the Providence City Hospital in Providence, Rhode Island.
Sister Elizabeth Kenny (1880-1952)
Sister Kenny demonstrating her therapy for polio patients to another nursing sister in a hospital in Queensland c1939. (Contributed by Dr. Douglas Lanska. Courtesy of the John Oxley Library, State Library of Queensland. Copyright ...
After this, the manufacture of "iron lungs" expanded markedly over the next 2 decades. At their peak use in the early 1950s, wards at some referral centers were crowded with dozens of these devices, all in use for affected patients, with a large complement of attendant nursing and respiratory therapy staff. Indeed, the iron lung required intensive nursing care and respiratory therapy and a supporting hospital infrastructure.
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Iron lung respirator
Emerson tank respirator (“iron lung”) in use during a poliomyelitis epidemic in Rhode Island in 1960. (Contributed by Dr. Douglas Lanska. Centers for Disease Control and Prevention. Public domain.)
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Man with polio in an iron lung visiting with his family
If a polio patient's diaphragm was compromised, the early treatment was use of the iron lung, a form of negative pressure ventilator. (Photo ID: NPC 3631. Source collection: OHA 250: New Contributed Photographs. Repository: Nat...
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A boy with polio in the Emerson Respirator (iron lung) viewing the photographer (Joe Clark) in the machine's mirror, circa 1955 (Herman Kiefer Hospita...
An Emerson Respirator, also known as an iron lung, was a machine that enabled a person to breathe on their own when muscle control had been lost (often due to poliomyelitis). It used negative pressure ventilation to induce inha...
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Nurse shares a smile with a child inside of an iron lung, circa 1960-1968
(Creator: U.S. Air Force. File name: 244001_1370. Citation: Mayor John F Collins records, Collection #0244.001, City of Boston Archives, Boston. Creative Commons Attribution 2.0 Generic License [CC BY 2.0], https://creativecomm...
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A boy in an iron lung at the Naval Hospital, circa 1960
(Photo by Don Pinder. Courtesy of the Florida Keys Public Library. Creative Commons Attribution 2.0 Generic License [CC BY 2.0], https://creativecommons.org/licenses/by/2.0.)
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Woman in an iron lung looks at herself in a mirror
(Source: Oakenroad. Creative Commons Attribution 2.0 Generic License [CC BY 2.0], https://creativecommons.org/licenses/by/2.0.)
From the 1920s through at least the early 1940s, the orthodox treatment for poliomyelitis consisted largely of absolute and prolonged immobilization of affected limbs with splints or plaster casts, followed by often permanent orthopedic braces; in retrospect, this approach was less than ideal, and in many ways counterproductive as it caused or contributed to disuse atrophy, joint contractures, and lifelong disability. Beginning around 1911, in a sparsely populated area of Australia, “Sister” Elizabeth Kenny (1880-1952) developed an empiric approach to rehabilitation following poliomyelitis that combined physical and psychological techniques.
Iron-lung ward at Rancho Los Amigos Hospital
Iron-lung ward at Rancho Los Amigos Hospital, Downey (Los Angeles County), California, c1953. (Contributed by Dr. Douglas Lanska. Courtesy of the Rancho Los Amigos National Rehabilitation Center (Rancho Los Amigos) in Downey, Cali...
The physical methods she employed included the labor-intensive application of moist warm wraps for muscle spasms, passive range of motion, and massage. Kenny’s physical methods were combined with early mobilization, strong encouragement to achieve both functional independence and a prompt return to normal activities, and confident optimism for improvement. The Kenny methods were widely adopted in the United States and elsewhere in the 1940s (although not in Australia where she was strongly opposed by physicians and, particularly, orthopedic surgeons). Kenny’s approach represented a significant advance in the care of paralyzed patients and helped foster the growth of physical therapy and the medical discipline of physical medicine and rehabilitation.
The first modern intensive care unit was established in Copenhagen in response to the polio epidemic in 1952, based on experience gained using positive pressure ventilation to save hundreds of patients during that epidemic (123; 181).
It was not until the development of the first successful inactivated poliovirus vaccine in the 1950s by American virologist Jonas Salk that the severity of polio epidemics started to decrease. In 1954 and 1955, Salk’s inactivated poliovirus vaccine was successfully tested in a monumental, controlled trial involving more than 1.8 million United States schoolchildren funded by the National Foundation for Infantile Paralysis (131).
Jonas Salk (1914-1995)
American virologist Jonas Salk (1914-1995) in 1988. Salk developed the first effective trivalent killed-virus poliovirus vaccine. (Contributed by Dr. Douglas Lanska. Courtesy of the U.S. Public Health Image Library.)
Salk's vaccine dramatically curtailed cases of polio in the United States, but one of the difficulties was the required injection.
Girl receiving Salk polio vaccination
A young girl receiving her Salk polio vaccination in her left upper arm. The girl was among local residents who had lined up at this mobile polio vaccination clinic. This photograph was taken in 1963, when the U.S. was shifting...
Various images of children in wheelchairs or wearing leg braces were used to encourage people to support the March of Dimes and to encourage vaccination.
Image encouraging individuals to receive polio vaccinations
Images like this were used to encourage individuals to receive polio vaccinations, which were made available in April 1955. (Source: CDC. U.S. Centers for Disease Control and Prevention, Public Health Image Library. Public doma...
Polish-American virologist Albert Sabin (1906-1993) developed the first effective trivalent live-attenuated (oral) poliovirus vaccine, with somewhat different sources and processes used for component vaccines for poliovirus types 1, 2, and 3 to ensure that each had low neurovirulence (63).
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Passage histories from the wild type polioviruses to isolate the Sabin OPV1, OPV2, and OPV3
The viruses were replicated either in vivo on monkey (MK) or mouse (Mo) or in vitro. The in vitro cultures used cells from different tissues (cynomolgus monkey kidney cells, rhesus monkey testicular or skin tissues). At the dif...
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Genomic organization of the wild type poliovirus (Mahoney strain) and the Sabin live attenuated poliovirus vaccine
(Upper panel) Mahoney virus. P1 is the precursor of the capsid proteins; P2 and P3 are the precursors of the noncapsid proteins. The genome segment from nucleotide 743 to 3,832 encodes a polyprotein precursor amino acids 1 to 1...
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Albert Sabin (1906-1993)
Polish-American virologist Albert Sabin (1906-1993) developed the first effective trivalent live-attenuated (oral) poliovirus vaccine. (Contributed by Dr. Douglas Lanska. Source: Woodward T. The Armed Forces Epidemiological Boa...
Sabin's first oral poliovirus vaccine, for use against type 1 polioviruses, was licensed in the United States in 1961. His vaccines for type 2 and type 3 polioviruses were licensed in 1962.
The oral live-attenuated Sabin vaccine was easier to administer and produced longer-lasting immunity than the killed-virus Salk vaccine that had to be administered by injection.
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Healthcare worker dropping oral poliovirus vaccine on sugar cubes prior to immunization administration
(Source: CDC, 1961. U.S. Centers for Disease Control and Prevention, Public Health Image Library. Public domain.)
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Child receiving oral polio vaccine
This mother was cradling her child, as he received an oral polio vaccine, which would prevent the baby from acquiring the highly infectious disease poliomyelitis (polio), caused by the poliovirus. Beginning in 1988, the efforts...
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Girl receiving her polio immunization by way of a sugar cube
A young girl receiving her polio immunization by way of an orally administered sugar cube at a Dekalb County, Georgia, well-child clinic. (Source: CDC/Meredith Hickson, 1977. U.S. Centers for Disease Control and Prevention, Pub...
So, by 1962, the Sabin vaccine began replacing the Salk vaccine in the United States and in many other countries.
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Historical photograph of boxes of poliovirus vaccine
Two workers standing beside a cart loaded with boxes containing poliovirus vaccine, produced at the time by the Wyeth pharmaceutical company. (Source: CDC/ Mr. Stafford Smith, 1963. U.S. Centers for Disease Control and Preventi...
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Long line of people waiting for polio vaccinations in San Antonio, Texas
Aerial view of a long line of people waiting for their polio vaccinations. The line surrounded the city auditorium in San Antonio, Texas. (Source: CDC/Mr. Stafford Smith, 1962. U.S. Centers for Disease Control and Prevention, P...
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Somali mother holding her infant steady for oral polio vaccine
A Somali mother holding her child steady, while a "Stop Transmission of Polio" (STOP) worker administered the oral polio vaccine to the young infant. WHO and UNICEF, working in conjunction with national Ministries of Health, re...
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Unvaccinated children receiving oral polio vaccine in Pakistan
A Pakistani Field Epidemiology Training Program (FETP) 2nd cohort resident, (Dr. Muhammad Dawood Kasi) administering oral polio vaccine (OPV) to unvaccinated children in the union council locality of Kharotabad, Balochistan, Pa...
When necessary, the National Guard distributed polio vaccines to areas experiencing epidemics.
Alabama National Guard preparing to fly polio vaccine to Haleyville during the polio epidemic of 1963
Scene at a Birmingham, Alabama airport, where the Alabama National Guard was preparing to fly polio vaccine to Haleyville during the polio epidemic of 1963. (Source: CDC/Mr. Stafford Smith, 1963. U.S. Centers for Disease Contro...
Public-health promotional campaigns for polio vaccination in the early 1960s used the Communicable Disease Center’s national symbol of public health, the "Wellbee" (Note that the Communicable Disease Center was the original name for the CDC, which changed in 1970 to the Center for Disease Control, and in 1992 to the Centers for Disease Control and Prevention).
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1963 poster: “Wellbee,” reminding the public to "be well, be clean, wash your hands” (1)
This 1963 poster featured what at that time, was the Communicable Disease Center’s (CDC) national symbol of public health, the "Wellbee," who was reminding the public to "be well, be clean, WASH YOUR HANDS." CDC used Wellbee in...
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1963 poster: “Wellbee,” reminding the public to "be well, be clean, wash your hands” (2)
This 1963 poster featured what at that time, was the Communicable Disease Center’s (CDC) national symbol of public health, the "Wellbee," who was reminding the public to "be well, be clean, WASH YOUR HANDS". CDC used Wellbee in...
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1964 poster: “Wellbee,” reminding the public to "be well, be clean, wash your hands”
This 1964 poster featured what at that time, was the Communicable Disease Center’s (CDC) national symbol of public health, the "Wellbee," who was reminding the public to "be well, be clean, WASH YOUR HANDS." CDC used Wellbee in...
Clinical manifestations
Presentation and course
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• More than 90% of poliovirus infections are asymptomatic. |
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• Approximately 4% to 8% of infected patients develop symptoms of acute poliomyelitis, which can be separated into two distinct clinical phases: the “minor illness,” with an incubation period of 3 to 7 days, and the “major illness,” with onset of symptoms generally 9 to 12 days after exposure. |
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• During the major illness, patients may demonstrate signs of meningeal irritation, asymmetric flaccid weakness, muscle spasms, normal or accentuated muscle stretch reflexes, and hyperesthesias with preserved somatosensation. |
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• Paralytic poliomyelitis accounts for only 0.1% to 2.0% of all poliovirus infections and can be divided into three types: spinal, bulbar, and bulbospinal. |
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• Chronic poliomyelitis infections have occurred infrequently in children with immunodeficiencies who have received the live oral vaccine. |
More than 90% of poliovirus infections are asymptomatic. Approximately 4% to 8% of infected patients develop symptoms of acute poliomyelitis, which can be separated into two distinct clinical phases: the “minor illness,” with an incubation period of 3 to 7 days, and the “major illness,” with onset of symptoms generally 9 to 12 days after exposure (100). During the minor illness, patients present with constitutional symptoms (eg, fever, headache, nausea and vomiting, coryza, and sore throat), which are typically self-limiting, lasting 1 to 2 days. Major illness is associated with CNS infection, which has been estimated to occur in 0.1% to 1.0% of all poliovirus infections (159; 173).
During the major illness, patients may demonstrate signs of meningeal irritation, asymmetric flaccid weakness, muscle spasms, normal or accentuated muscle stretch reflexes, and hyperesthesias with preserved somatosensation. The major illness includes all forms of CNS disease caused by poliovirus, including aseptic meningitis, polioencephalitis, bulbar polio, and paralytic poliomyelitis. These manifestations may occur alone or in combination. About one third of young children who develop the major illness experience a biphasic illness with symptoms of the minor illness preceding onset of CNS disease (98; 240). The major illness often begins with aseptic meningitis. One third of cases are limited to meningitis without detectable motor neuron impairment, which resolves within 5 to 10 days. Polioencephalitis can occur as well, manifesting as obtundation or agitation, autonomic dysfunction and upper motor neuron signs of spasticity, increased deep tendon reflexes, and Babinski signs. Muscle pains, muscle cramps, fasciculations, and radicular pain rarely occur without paralysis, which they precede by 24 to 48 hours.
Paralytic poliomyelitis accounts for only 0.1% to 2.0% of all poliovirus infections and can be divided into three types: spinal, bulbar, and bulbospinal (159; 99; 164). Muscle weakness is preceded by intense myalgias of the involved limbs and the axial skeleton, and it may be relieved by exercise. The hallmark of paralytic poliomyelitis is asymmetric motor paresis, which ranges from mild weakness of a single extremity to complete quadriplegia and respiratory muscle paralysis.
Hospitalized child with poliomyelitis during the 1960 Rhode Island polio epidemic
Dr. Joseph Oren, Chief of the CDC Poliomyelitis Surveillance Unit, was examining the child, who was displaying signs of respiratory weakness. A suction machine was being used, in conjunction with a tracheostomy tube to help in ...
Proximal limb muscles are more involved than distal, and legs are more commonly involved than arms. The reflexes are initially brisk and then become absent over time. The pace of development of the paresis ranges from several hours to several days. Rarely, transverse myelitis with paraparesis, urinary retention, sensory complaints and signs, and autonomic dysfunction may be seen (189; 78). Bulbar poliomyelitis occurs in 5% to 35% of paralytic cases and most commonly affects the ninth and tenth cranial nerves.
Some affected patients develop profound leg weakness that produces severe secondary orthopedic problems, limb deformities, and contractures. Common resulting neuro-orthopedic deformities are pes equinovarus and paralytic pes cavus.
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Infantile spinal paralysis (poliomyelitis)
Late stage, extreme atrophy of the lower portion of the trunk, the pelvic region, and the legs; marked pes varus, right side. (Source: Bing R. A textbook of nervous diseases for students and practising physicians in thirty lect...
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Pes equinovarus from poliomyelitis
(Source: Bing R. A textbook of nervous diseases for students and practising physicians in thirty lectures. Authorized translation by Charles L Allen. New York: Rebman Co, 1921.)
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Paralytic pes cavus from poliomyelitis
(Source: Bing R. A textbook of nervous diseases for students and practising physicians in thirty lectures. Authorized translation by Charles L Allen. New York: Rebman Co, 1921.)
Acquired quadrupedal human gait. In the past, poliomyelitis was the most common cause of an acquired quadrupedal human gait (as distinct from normal developmental or volitional quadrupedal gaits) (134). The most dramatic example was the boy photographed by English American photographer Eadweard Muybridge (1830-1904) and American neurologist Francis Xavier Dercum (1856-1931) in 1885.
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Sequential lateral images of a boy with a lateral sequence quadrupedal (hands-and-feet bear crawl) gait after poliomyelitis
The images are from Plate 539 in Muybridge’s Animal Locomotion (Muybridge E. Animal locomotion: an electrophotographic investigation of consecutive phases of animal movements, 1872-1885. Philadelphia: University of Pennsylvania...
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Single image from photographic sequence of a boy with a lateral sequence quadrupedal (hands-and-feet bear crawl) gait after poliomyelitis
Note the accentuated anterior pelvic tilt and lumbar lordosis producing a swayback posture, the marked atrophy of the leg muscles, and the back-kneeing (genu recurvatum). The images are from Plate 539 in Muybridge’s Animal Loco...
In a large series of patients hospitalized with poliomyelitis, 3 of 98 patients (3%) with disturbances of locomotion were noted to be “hand walkers” (among a total of 108 for whom function was recorded) (95). Note that the term “hand walkers” generally denoted those that walked with a quadrupedal gait but very rarely referred to individuals who learned to walk exclusively on their hands. Early 20th-century cases of acquired quadrupedal gaits following poliomyelitis, with photographic documentation of a quadrupedal stance were reported, for example, by Austrian pediatrician and neurologist Julius Zappert (1867-1942), Austrian orthopedist Hans Spitzy (1872-1956), German orthopedic surgeon Oskar Vulpius (1867-1936), and German Swiss neurologist Robert Paul Bing (1878-1956) (249; 180; 219; 106; 30; 134).
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Polio "handwalker" with quadrupedal (hands-and-knees crawl) gait after poliomyelitis (1)
Case of Hans Spitzy (1912). "Handwalker" girl, 7 years of age. All of the muscles in both legs, except the iliopsoas of each side, are paralyzed. The child can get around only by crawling. Duration of paralysis was 5 years. (So...
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Polio "handwalker" 1 year later
Case of Austrian orthopedist Hans Spitzy (1912). "The patient can walk a little in erect posture after arthrodesis in both knees. To prevent post-operative curvature [of the legs] she wears celluloid braces (for 2 years)." (Sou...
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Polio "handwalker" with quadrupedal (hands-and-knees crawl) gait after poliomyelitis (2)
Case of German orthopedist Oskar Vulpius (1915). Boy using a hands-and-knees crawl: infantile spinal paralysis (handwalker) (observation of Professor O Vulpius, Heidelberg). (Source: Ibrahim J. Poliomyelitis anterior acuta [acu...
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Polio "handwalker" with quadrupedal (hands-and-feet bear crawl) gait after poliomyelitis (1)
Case of Swiss neurologist Robert Bing (1921). Boy using a hands-and-feet bear crawl: infantile spinal paralysis. So-called "handwalker" as a result of severe dorsal and lumbar poliomyelitis. Note the marked atrophy in the pelvi...
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Polio "handwalker" with quadrupedal (hands-and-feet bear crawl) gait after poliomyelitis (2)
Case of Austrian pediatrician Heinrich Lehndorff (1908). Poliomyelitis in a 7-year-old child. Severe paralysis of both legs. Flexion contracture in the hip joint, severe lordosis of the lumbar spine. "Hand walkers." [Case] of D...
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Polio "handwalker" pulling himself to a semi-standing position using a chair
Case of Austrian pediatrician Heinrich Lehndorff (1908). Note the extreme lumbar lordosis, reflecting a combination of weakness and hip contractures.
Sources:
Zappert J. Die Epidemie der Poliomyelitis acuta e...
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Neurologic examination of a boy with residua of poliomyelitis
Latin-American nurse performing a neurologic examination on a boy with residua of poliomyelitis. Note the severe atrophy of muscles in both lower legs and the callouses over the knees and possible effusion of the knee joint, in...
Vulpius’s case (as illustrated by German physician J Ibrahim in a textbook chapter titled “The organic nervous diseases of childhood”) used hands-and-knees crawling, whereas the cases of Bing and Zappert used hand-and-feet crawling. More recent examples of quadrupedal gaits in adults who survived poliomyelitis as children were identified in various countries during the latter half of the 20th century, most often in Africa and Asia (134).
Chronic poliomyelitis infections have occurred infrequently in children with immunodeficiencies who have received the live oral vaccine (198; 248; 246). Onset usually occurs several months after vaccination, and patients may present with a lower motor neuron paralysis or progressive cerebral dysfunction.
Post-polio syndrome. As many as 20% to 30% of patients who recover from paralytic poliomyelitis experience new onset of slowly progressive muscle weakness, pain, atrophy, and fatigue many years after the acute illness, most commonly 3 to 4 decades after acute illness (117; 139; 140; 51). This is known as post-polio syndrome. Both muscle and joint pain are frequent. Patients with a history of bulbar poliomyelitis are particularly at risk of developing dysphagia as well as sleep-disordered breathing abnormalities.
In a retrospective study of 400 patients with poliomyelitis attending a specialized outpatient clinic in Barcelona, Spain, post-polio syndrome was more frequent in women (58%) (209). The mean age at symptom onset was 52 years and was earlier in women. Common problems included pain (85%), loss of strength (40%), fatigue (66%), cold intolerance (20%), dysphagia (12%), depressive symptoms (32%), and cognitive complaints (9%). Fatigue or tiredness, depression, and cognitive complaints were significantly more frequent in women. Electromyographic findings suggestive of post-polio syndrome were reported in 59%.
Prognosis and complications
Morbidity and mortality in poliomyelitis vary depending on the severity of illness. Although a minor illness typically causes little or no sequelae, major illness can lead to muscle paralysis, respiratory arrest, and death. Case fatality is 1.5% to 6.7%, assuming availability of optimal care (67). A study on a particularly virulent outbreak of wild poliovirus in the Republic of Congo found up to 92% of cases had residual paralysis 60 days after disease onset (185). Efficient surveillance and proactive case management may improve morbidity and mortality. Complications of poliomyelitis include respiratory distress often necessitating mechanical ventilation, dysphagia, and pneumonia (77; 80). Prolonged immobility may lead to decubitus ulcers and limb contractures (80). Provocative paralysis (which can occur following intramuscular injection) should also be anticipated when managing poliomyelitis.
Orthopedic issues include hip, back, and extremity pain; muscle strain; ligament sprain; spondylosis; kyphoscoliosis; exaggerated lumbar lordosis; genu recurvatum; and other deformities (54; 80; 225).
Child with gene recurvatum as a residua of polio
Gene recurvatum as a residua of polio generally results from persistent mechanical trauma from hyperextending the knee to provide adequate support when the quadriceps is severely weakened. (Contributed by Dr. Douglas Lanska. Cente...
In the past, poliomyelitis was probably the most common cause of an acquired quadrupedal human gait (as opposed to normal developmental or volitional quadrupedal gaits) (132; 133; 134).
Postpoliomyelitis patients transitioning to adulthood have a high frequency of falls, osteoporosis, and fractures (217). Bone mineral density tends to be worse in the worst-affected leg (217). In a retrospective analysis of 204 postpoliomyelitis patients, recurrent falls were documented in 39% of patients and osteoporosis in 21%. Not surprisingly, osteoporosis was more frequent in women and patients with fractures. At least one fracture occurred in half (52%) of the patients and more than one fracture occurred in 40% of the patients. The median age for the first fracture was 58 years (range, 30 to 83 years) and most fractures occurred in the affected limb (73%).
Sleep disturbances also occur more frequently and are most commonly associated with the bulbar variant of poliomyelitis (54; 75; 13).
Physical disabilities experienced often lead to emotional symptoms (80). Psychotherapy, group rehabilitation, regular follow-ups, and patient education methods can be used to improve mental status and overall well-being (75).
Patients with post-polio syndrome develop generalized fatigue, muscle weakness, atrophy, pain, fasciculations, cramps, and cold intolerance occurring several years (usually more than 15 years) after the acute episode (93; 54; 117; 139; 140; 51).
Clinical vignette
A 10-year-old boy living in Nigeria was brought to the pediatric emergency department for evaluation of a 2-day history of malaise and diarrhea, with both an increased frequency of stooling and the passage of watery, non-bloody stools. On examination, he was febrile with a temperature of 38.5 degrees Celsius. His abdomen was non-tender, and he had no palpable organomegaly. On neurologic examination, he was conscious and fully oriented but lethargic with mild neck stiffness. He had no cranial nerve palsy. Muscle tone was mildly reduced in the right leg compared to the left. Power was grade 4/5 on the Medical Research Council scale in the right ankle and 5/5 in all other muscle groups. Deep tendon reflexes were grade 1 at the right ankle and grade 2 at the other sites. Plantar response was flexor bilaterally. Sensory examination was unremarkable. Complete blood count, erythrocyte sedimentation rate, electrolytes, and stool (for microscopy, culture, and sensitivity) were ordered.
The following day, his motor strength was reduced to 3/5 in the right leg, and within 48 hours, it was 1/5 and 4/5 on the right and left legs, respectively. Blood count was unremarkable. CSF analysis revealed a mild increase in leukocytes (18 cells/µl) and protein (45 mg/dl). CSF glucose was normal (70 mg/dl). Stool was negative for pathogenic bacteria or blood. Stool samples were positive for wild-type poliovirus 1. He was maintained on bed rest, and specific instruction was given to be vigilant for respiratory distress and to avoid intramuscular injections.
Further interview with the mother revealed that the boy did not complete his polio immunizations as he had only the oral polio vaccine 1 at 6 weeks after birth but did not receive the second and third oral polio vaccine doses in the subsequent months. She could not remember if he had any booster doses at 18 months or later. Three weeks later, power was 2/5 on the right and 4/5 on the left legs.
Biological basis
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• Poliomyelitis is an infection caused by the polioviruses, which are human enteroviruses. |
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• Poliovirus, as with other enteroviruses, is most commonly spread by fecal-hand-oral transmission. |
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• Although the precise cause of post-polio syndrome is unknown, the cause is probably related to overstress or exhaustion of the residual surviving motor units following acute poliovirus infection. |
Etiology and pathogenesis
Poliomyelitis is an infection caused by the polioviruses, which are human enteroviruses. Three poliovirus serotypes are distinguished from one another by type-specific antisera (09). Before the introduction of poliovirus vaccines, naturally occurring polioviruses circulated in temperate climates with a marked seasonal variation resulting in peak activity between July and October and low levels between December and May. Poliovirus type 1 was responsible for 80% to 90% of all epidemics of paralytic poliomyelitis in the United States (27; 173).
Poliovirus is a nearly spherical icosahedral-shaped virus, as revealed by x-ray crystallography and electron microscopy.
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Single poliovirus virion
3-dimensional representation of a single poliovirus virion. Photograph by Meredith Boyter Newlove MS, James Archer MS. (Contributed by Dr. Douglas Lanska. Centers for Disease Control and Prevention. Public domain.)
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Three-dimensional structural view of the icosahedral-shaped poliovirus type 3 based on x-ray diffraction
(Source: Filman DJ and Hogle JM (1989) [https://www.rcsb.org/structure...]. Creative Commons Attribution-Share Alike 4.0 International [CC BY 4.0] license, creativecommons.org/l...
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Round polio virions, or virus particles, scattered on a background plane
Scanning electron microscopic (SEM) image depicted a number of round, polio virions, or virus particles, scattered on a background plane. (Source: CDC. U.S. Centers for Disease Control and Prevention, Public Health Image Librar...
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Ultrastructural features exhibited by numerous icosahedral-shaped poliovirus particles
This transmission electron microscopic image reveals ultrastructural features exhibited by numerous icosahedral-shaped poliovirus particles. (Source: CDC/ Dr. Fred Murphy, Sylvia Whitfield (1975). U.S. Centers for Disease Contr...
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Poliovirus type-1 virions
Transmission electron microscopic image depicting numerous, round, poliovirus type-1 virions, which measure 20-30nm in diameter, and exhibit icosahedral symmetry. (Source: CDC/ Dr. Joseph J. Esposito; F. A. Murphy, 1971. U.S. C...
The poliovirus genome consists of a single-stranded, positive-sense polarity RNA molecule, which encodes a single polyprotein (61).
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Genomic structure of poliovirus type 1 (Mahoney)
The poliovirus genome consists of a single-stranded, positive-sense polarity RNA molecule, which encodes a single polyprotein. The 5' non-translated region (NTR) harbors two functional domains, the cloverleaf and the internal r...
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Secondary structure of the poliovirus type 1 (Mahoney) 5' non-translated region (NTR)
This genomic region has been divided into six domains (I to VI), of which domain I constitutes the cloverleaf and the remaining domains comprise the internal ribosome entry site (IRES). Spacer sequences without complex secondar...
The 5' non-translated region (NTR) harbors two functional domains, the cloverleaf and the internal ribosome entry site (IRES). The 5' NTR is covalently linked to the viral protein VPg.
The cellular life cycle of poliovirus is somewhat complicated (39; 61).
Cellular life cycle of poliovirus
(1) First, poliovirus binds to the cell surface macromolecule CD155, which functions as the receptor. (2) Uncoating the viral RNA is mediated by receptor-dependent destabilization of the virus capsid. (3) Cleavage of the viral ...
First, poliovirus binds to the cell surface macromolecule CD155, which functions as the virus receptor (61). Viral RNA uncoating is mediated by receptor-dependent conformational changes and destabilization of the virus capsid (39; 61).
Model of poliovirus entry
After binding to cell-surface receptors, poliovirus (160S) undergoes conformational changes of the capsid to the 135S form. The 135S particles are then internalized by an actin- and tyrosine kinase-dependent, but clathrin- and ...
The particles are then internalized by an actin- and tyrosine kinase-dependent, but clathrin- and caveolin-independent, mechanism (39). The release of the viral genome takes place only after internalization from an endocytotic compartment localized within 100 to 200 nm of the plasma membrane (39). On release of the RNA genome, the empty capsid is transported away along microtubules (39). Translation of the viral RNA is mediated by internal ribosome entry site (IRES), an RNA element that allows for translation initiation in a cap-independent manner, as part of protein synthesis. Proteolytic processing of the viral polyprotein produces mature structural and nonstructural proteins. The positive-sense RNA serves as the template for complementary negative-strand synthesis. Newly synthesized positive-sense RNA molecules can either serve as templates for translation or associate with capsid precursors to undergo encapsidation, which ultimately generates progeny virions. Lysis of the infected cell results in release of infectious progeny virions.
Poliovirus, as with other enteroviruses, is commonly spread by fecal-hand-oral transmission (63).
Oral transmission of polioviruses (contained in water or food) and their colonization of the gastrointestinal tract
Major risk factors for poliovirus transmission include poor sanitation and hygiene conditions, high population density, and tropical or subtropical climate. (A) Polioviruses infect humans by the fecal-oral route. This acid-resi...
After ingestion, the poliovirus implants in the oropharynx and small bowel and penetrates the mucosa via specialized microfold cells and other epithelial cells overlying submucosal lymphoid tissues (99; 182; 177). After replication in the submucosal lymphatic tissue, the virus spreads to the lymph nodes, and then to the bloodstream (32). In a minority of infections, further replication of virus in reticuloendothelial tissues leads to a major viremia. CNS invasion is much more likely to occur during secondary viremia but can infrequently occur during primary viremia. As demonstrated in experimental studies in primates, tonsils, mesentery lymph nodes, and intestinal mucosa are major target sites of viral replication (216). Early in the infectious process, poliovirus replication occurs in both epithelial cells (which accounts for virus shedding in the gastrointestinal tract) and lymphoid/monocytic cells in tonsils and Peyer patches (which accounts for viremia) (216). Genetic variants in innate immune defenses and cell death pathways may contribute to the clinical presentation of poliovirus infection (12).
The exact route through which poliovirus enters the CNS is unclear (170; 171; 172; 177). There is some suggestion based on animal models that viral replication in skeletal muscles precedes transport of poliovirus to the spinal cord via the peripheral nerve (36). The anterior horn cells and other motor neurons are selectively vulnerable to poliovirus infection (33; 112; 94; 56). Mitochondria are important in poliovirus-induced apoptosis and mitochondrial dysfunction results from an imbalance between pro- and anti-apoptotic pathways (31). Pathologic changes occur within 1 to 2 days after poliovirus infects the neuron, and an inflammatory response ensues with meningeal, perivascular, and parenchymal infiltrates (35; 34; 110; 245). Neuronal destruction by lytic replication of the poliovirus causes paralytic poliomyelitis in less than 1% of those infected (177). Individuals who have had polio may experience denervation with subsequent reinnervation for many years. Many have spotty loss of anterior horn motor neurons, and the anterior horn may be shrunken and sclerotic in the chronic stage.
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Spinal cord tissue sample revealing polio type III degenerative changes (low magnification)
Photomicrograph of a spinal cord tissue sample at low magnification in the region of the anterior horn, revealing polio type III degenerative changes. (Source: CDC/Dr. Karp, Emory University, 1964. U.S. Centers for Disease Cont...
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Spinal cord tissue sample revealing polio type III degenerative changes (high magnification)
Photomicrograph of a spinal cord tissue sample at higher magnification in the region of the anterior horn, revealing polio type III degenerative changes. (Source: CDC/Dr. Karp, Emory University, 1964. U.S. Centers for Disease C...
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Spinal cord following acute anterior poliomyelitis (1)
Late-stage, carmine preparation from the spinal cord of a 76-year-old man. The cells of the anterior horn, still recognizable microscopically, are brought out by retouching. (Source: Bing R. A textbook of nervous diseases for s...
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Spinal cord following acute anterior poliomyelitis (2)
Poliomyelitis acuta having run its course. Section of the lumbar cord; staining according to Weigert. Narrowing of the left half of the spinal cord section; atrophy and sclerosis of the anterior horn; degeneration of the anteri...
Although the precise cause of post-polio syndrome is unknown, the cause is probably related to overstress or exhaustion of the residual surviving motor units following acute poliovirus infection. Terminal elements of surviving alpha motor neurons that sprout to reinnervate adjacent myofibrils following initial infection are believed to become overstressed (91; 04; 183; 215; 124). Muscle fatigue in post-polio syndrome may be due to impaired activation beyond the muscle membrane at the level of excitation-contraction coupling or may have a central origin. Other possible mechanisms have been considered, including immunologic events and other virus-host interactions (60), but some studies have found no evidence of a dysimmune condition (124).
Vaccine-derived polioviruses and vaccine-associated paralytic poliomyelitis. Vaccine-derived poliovirus (VDPV) results from the use of oral poliovirus vaccine in low- and middle-income countries. VDPVs are rare strains of poliovirus that have genetically mutated from the attenuated strains contained in the oral polio vaccine. Normally, when a child is vaccinated, the weakened vaccine strains replicate in the intestine and enter the bloodstream, triggering a protective immune response. Rarely, during this replication process, some vaccine virus may genetically mutate from the original attenuated strain, become neurovirulent, and cause vaccine-associated paralytic poliomyelitis. In addition, like infections with wild polioviruses, vaccinated children typically excrete the vaccine strains of poliovirus for 6 to 8 weeks. If a population is under-immunized, there may be enough susceptible children for the excreted attenuated poliovirus to begin circulating in the community; with uninterrupted recirculation, the attenuated vaccine strain may reacquire neurovirulence, at which time these are called circulating vaccine-derived polioviruses (cVDPV). Prolonged replication of VDPV has also been observed in people with immune deficiency disorders. In the absence of an adequate immune response, such individuals may excrete immunodeficiency-related VDPVs (or iVDPVs) for prolonged periods. Most patients with iVDPVs either stop excretion within 6 months or die. Finally, ambiguous VDPVs (aVDPVs) are either isolated from people with no known immunodeficiency or isolated from sewage whose ultimate source is unknown. As poliovirus serotypes are eliminated, it is necessary to continue to shift away from the use of live attenuated vaccines to minimize the risk of VDPV.
Therefore, there are three categories of VDPV:
(1) Circulating VDPVs (cVDPVs): VDPV for which there is evidence of human-to-human transmission in the community. Isolates must either be from (1) at least two individuals (not necessarily cases of acute flaccid paralysis) who are not direct contacts; (2) from one individual plus environmental samples; or (3) from at least two environmental samples collected more than 2 months apart or from more than one distinct collection site. Low levels of population immunity to polio (due to low vaccination coverage) increase the risk of cVDPV (07; 08).
(2) Immunodeficiency-associated VDPVs (iVDPVs): VDPV isolated from patients with primary immunodeficiencies. Patients with iVDPV are potential poliovirus reservoirs that can potentially reintroduce polioviruses into a community in the post-eradication era. Roughly a third of patients with iVDPVs have never had paralysis (212).
(3) Ambiguous VDPVs (aVDPVs): VDPV isolates (human or environmental) without evidence of circulation and from individuals with no known immunodeficiency. These may subsequently be reclassified as “circulating” if genetically linked isolates are identified.