Classification

General Characteristics and Epidemiology

General characteristics of poliovirus

• Family: Picornaviridae
• Genus: Enterovirus
• Classified as a strain of Enterovirus C
• RNA RNA Ribonucleic acid (RNA), like deoxyribonucleic acid (DNA), is a polymer of nucleotides that is essential to cellular protein synthesis. Unlike DNA, RNA is a single-stranded structure containing the sugar moiety ribose (instead of deoxyribose) and the base uracil (instead of thymine). RNA generally carries out the instructions encoded in the DNA but also executes diverse non-coding functions. RNA Types and Structure virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology: Overview:
  • Linear
  • Single-stranded
  • Positive-sense
  • Functions as mRNA
• Diameter: 25–30 nm
• Icosahedral symmetry
• Lacks a lipid envelope
• Acid-stable

Clinically relevant species

Poliomyelitis is caused by 3 serotypes of poliovirus:

• Wild type 1 (most common)
• Wild types 2 and 3 (considered eradicated)

Epidemiology

• Poliovirus has been eradicated in most countries because of extensive vaccination Vaccination Vaccination is the administration of a substance to induce the immune system to develop protection against a disease. Unlike passive immunization, which involves the administration of pre-performed antibodies, active immunization constitutes the administration of a vaccine to stimulate the body to produce its own antibodies. Vaccination efforts.
• 150 cases were reported in 2019.
• Endemic countries include: 
  • Pakistan
  • Afghanistan

Pathogenesis

Reservoir

Humans are the only known reservoir.

Transmission

This highly contagious virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology: Overview is transmitted via:

• Fecal–oral route
• Respiratory aerosols

Pathophysiology

• Oral entry of the virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology: Overview → replication in the oropharyngeal and GI lymphatic tissues
• Asymptomatic viremia → reticuloendothelial system
• If the infection is not contained → secondary viremia occurs → viral symptoms
• Virus enters the CNS (unclear process)
• Viral replication occurs in neurons of the spine (particularly the anterior horn) and brain stem Brain Stem The brain stem is a stalk-like structure that connects the cerebrum with the spinal cord and consists of the midbrain, pons, and medulla oblongata. It also plays a critical role in the control of cardiovascular and respiratory function, consciousness, and the sleep-wake cycle. Brain Stem → damage and necrosis → neurologic signs and symptoms

Clinical Presentation and Diagnosis

Abortive poliomyelitis

The majority of patients are asymptomatic or develop a minor flu-like illness:

• Fever
• Malaise
• Headache
• Pharyngitis Pharyngitis Pharyngitis is an inflammation of the back of the throat (pharynx). Pharyngitis is usually caused by an upper respiratory tract infection, which is viral in most cases. It typically results in a sore throat and fever. Other symptoms may include a runny nose, cough, headache, and hoarseness. Pharyngitis
• Nausea and vomiting

Nonparalytic poliomyelitis

Approximately 4% of patients will develop nonparalytic poliomyelitis. These patients will present with aseptic meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis after a prodrome similar to that of abortive poliomyelitis.

• Fever
• Headache
• Nuchal rigidity

Paralytic poliomyelitis

A minority of patients with nonparalytic poliomyelitis will progress to the paralytic form of the disease, characterized by:

• Muscle spasms
• Myalgias
• Profound, asymmetrical muscle weakness:
  • Legs most often affected
  • More severe in proximal muscles
• Diminished or absent reflexes
• Normal sensory exam
• Urinary retention
• Bulbar involvement:
  • Dysphagia Dysphagia Dysphagia is the subjective sensation of difficulty swallowing. Symptoms can range from a complete inability to swallow, to the sensation of solids or liquids becoming "stuck." Dysphagia is classified as either oropharyngeal or esophageal, with esophageal dysphagia having 2 sub-types: functional and mechanical. Dysphagia
  • Dysphonia
  • Difficulty handling secretions
  • Respiratory compromise
  • Autonomic dysfunction

Postpoliomyelitis syndrome

Postpoliomyelitis syndrome manifests as worsening symptoms in poliomyelitis survivors. It can occur decades after the initial infection.

• Fatigue
• Progressive weakness and atrophy of affected muscles
• Fasciculations
• Pain Pain Pain has accompanied humans since they first existed, first lamented as the curse of existence and later understood as an adaptive mechanism that ensures survival. Pain is the most common symptomatic complaint and the main reason why people seek medical care. Physiology of Pain
• Restless leg Leg The lower leg, or just "leg" in anatomical terms, is the part of the lower limb between the knee and the ankle joint. The bony structure is composed of the tibia and fibula bones, and the muscles of the leg are grouped into the anterior, lateral, and posterior compartments by extensions of fascia. Leg syndrome
• Respiratory insufficiency

Diagnosis

Diagnosis is based on clinical presentation and supported by the diagnostic workup.

Lumbar puncture:

• Often done in the setting of aseptic meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis
• Findings:
  • Moderate pleocytosis
  • ↑ Protein
  • Normal glucose

Specific testing:

• Viral culture
• PCR
• Serology

Management and Prevention

Management

There is no effective antiviral therapy for poliomyelitis. Management is supportive.

• Close hemodynamic monitoring for patients with bulbar involvement
• Mechanical ventilation for respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure or airway protection
• Analgesics for pain
• Splints to prevent deformities

Prognosis

Patients with nonparalytic poliomyelitis make complete recoveries. For those with paralytic poliomyelitis:

• 2 out of 3 patients will not regain full strength.
• 30%–40% will develop postpoliomyelitis syndrome.
• Mortality: 
  • 4%–6%
  • 10%–20% in adults or bulbar disease

Prevention

There are 2 vaccines used:

• Salk (inactivated poliovirus vaccine Vaccine A vaccine is usually an antigenic, non-virulent form of a normally virulent microorganism. Vaccinations are a form of primary prevention and are the most effective form due to their safety, efficacy, low cost, and easy access. Vaccination):
  • Given parenterally
  • Forms only IgG antibodies Antibodies Immunoglobulins (Igs), also known as antibodies, are glycoprotein molecules produced by plasma cells that act in immune responses by recognizing and binding particular antigens. The various Ig classes are IgG (the most abundant), IgM, IgE, IgD, and IgA, which differ in their biologic features, structure, target specificity, and distribution. Immunoglobulins, not IgA
• Sabin (oral poliovirus vaccine Vaccine A vaccine is usually an antigenic, non-virulent form of a normally virulent microorganism. Vaccinations are a form of primary prevention and are the most effective form due to their safety, efficacy, low cost, and easy access. Vaccination):
  • Live attenuated
  • Creates IgG and IgA
  • Not used in the United States
  • Patients shed the virus Virus Viruses are infectious, obligate intracellular parasites composed of a nucleic acid core surrounded by a protein capsid. Viruses can be either naked (non-enveloped) or enveloped. The classification of viruses is complex and based on many factors, including type and structure of the nucleoid and capsid, the presence of an envelope, the replication cycle, and the host range. Virology: Overview → may be able to mutate and circulate

Comparison of Enteroviruses

Differential Diagnosis

• Guillain–Barré syndrome (GBS): acute, rapidly progressive, acquired inflammatory neuropathy that can be triggered by infectious pathogens. Unlike poliomyelitis, the progressive muscle weakness in GBS is symmetric, there is sensory loss, and fever Fever Fever is defined as a measured body temperature of at least 38°C (100.4°F). Fever is caused by circulating endogenous and/or exogenous pyrogens that increase levels of prostaglandin E2 in the hypothalamus. Fever is commonly associated with chills, rigors, sweating, and flushing of the skin. Fever is rare. The diagnosis is clinical. A lumbar puncture will show a normal cell count and elevated protein. Management requires intensive care support, IV immune globulin, and plasma exchange.
• West Nile virus West Nile Virus West Nile virus is an enveloped, positive-sense, single-stranded RNA virus of the genus Flavivirus. Birds are the primary hosts and the disease is most often transmitted by Culex mosquitoes. Most people infected with West Nile virus are asymptomatic. Some patients develop West Nile fever (a self-limited, febrile illness) and a very small proportion of patients develop West Nile neuroinvasive disease. West Nile Virus infection: infection by a flavivirus. The majority of patients with West Nile virus West Nile Virus West Nile virus is an enveloped, positive-sense, single-stranded RNA virus of the genus Flavivirus. Birds are the primary hosts and the disease is most often transmitted by Culex mosquitoes. Most people infected with West Nile virus are asymptomatic. Some patients develop West Nile fever (a self-limited, febrile illness) and a very small proportion of patients develop West Nile neuroinvasive disease. West Nile Virus will be asymptomatic or have headache, myalgias and arthralgias, vomiting, diarrhea Diarrhea Diarrhea is defined as ≥ 3 watery or loose stools in a 24-hour period. There are a multitude of etiologies, which can be classified based on the underlying mechanism of disease. The duration of symptoms (acute or chronic) and characteristics of the stools (e.g., watery, bloody, steatorrheic, mucoid) can help guide further diagnostic evaluation. Diarrhea, or a rash. A small proportion develop encephalitis Encephalitis Encephalitis is inflammation of the brain parenchyma caused by an infection, usually viral. Encephalitis may present with mild symptoms such as headache, fever, fatigue, and muscle and joint pain or with severe symptoms such as seizures, altered consciousness, and paralysis. Encephalitis, meningitis Meningitis Meningitis is inflammation of the meninges, the protective membranes of the brain, and spinal cord. The causes of meningitis are varied, with the most common being bacterial or viral infection. The classic presentation of meningitis is a triad of fever, altered mental status, and nuchal rigidity. Meningitis, or flaccid paralysis. The diagnosis can be made with serology, PCR, and viral cultures. This will differentiate West Nile virus West Nile Virus West Nile virus is an enveloped, positive-sense, single-stranded RNA virus of the genus Flavivirus. Birds are the primary hosts and the disease is most often transmitted by Culex mosquitoes. Most people infected with West Nile virus are asymptomatic. Some patients develop West Nile fever (a self-limited, febrile illness) and a very small proportion of patients develop West Nile neuroinvasive disease. West Nile Virus from poliomyelitis. Management is supportive.
• Acute intermittent porphyria: rare, autosomal dominant Autosomal dominant Autosomal inheritance, both dominant and recessive, refers to the transmission of genes from the 22 autosomal chromosomes. Autosomal dominant diseases are expressed when only 1 copy of the dominant allele is inherited. Autosomal Recessive and Autosomal Dominant Inheritance disease that results in a deficiency of hydroxymethylbilane synthase. This deficiency leads to accumulation of heme precursors. Patients may experience abdominal pain, psychiatric symptoms, and peripheral neuropathies that can mimic GBS. Progression to quadriplegia and respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure can occur. The diagnosis is based on elevated porphyrin precursors in the urine. Management includes IV heme, dextrose, and trigger avoidance.
• Muscular dystrophy: group of noninflammatory muscle disorders caused by a mutation Mutation Genetic mutations are errors in DNA that can cause protein misfolding and dysfunction. There are various types of mutations, including chromosomal, point, frameshift, and expansion mutations. Types of Mutations in the DMD gene. This mutation Mutation Genetic mutations are errors in DNA that can cause protein misfolding and dysfunction. There are various types of mutations, including chromosomal, point, frameshift, and expansion mutations. Types of Mutations leads to muscle fiber destruction and replacement with fatty or fibrous tissue. Patients present with progressive proximal muscle weakness, which leads to the eventual loss of ambulation, as well as contractures, scoliosis Scoliosis Scoliosis is a structural alteration of the vertebral column characterized by a lateral spinal curvature of greater than 10 degrees in the coronal plane. Scoliosis can be classified as idiopathic (in most cases) or secondary to underlying conditions. Scoliosis, cardiomyopathy Cardiomyopathy Cardiomyopathy refers to a group of myocardial diseases associated with structural changes of the heart muscles (myocardium) and impaired systolic and/or diastolic function in the absence of other heart disorders (coronary artery disease, hypertension, valvular disease, and congenital heart disease). Overview of Cardiomyopathies, and respiratory failure Respiratory failure Respiratory failure is a syndrome that develops when the respiratory system is unable to maintain oxygenation and/or ventilation. Respiratory failure may be acute or chronic and is classified as hypoxemic, hypercapnic, or a combination of the two. Respiratory Failure. Unlike poliomyelitis, a marked elevation in CK may be observed. Genetic testing confirms the diagnosis. Management is supportive.   
• Multiple sclerosis Multiple Sclerosis Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease that leads to demyelination of the nerves in the CNS. Young women are more predominantly affected by this most common demyelinating condition. Multiple Sclerosis (MS): chronic inflammatory autoimmune disease leading to demyelination of the CNS. The clinical presentation of MS varies depending on the site of lesions, but it may include neurologic symptoms affecting vision, motor functions, sensation, and autonomic function. Diagnosis is made with MRI of the brain and spine, as well as CSF examination. Management involves corticosteroids for acute exacerbations and disease-modifying agents to slow progression of the disease.