Poliomyelitis

Essentials of Diagnosis

• Incubation period 7–14 days after exposure

• Headache, stiff neck, fever, vomiting, sore throat

• Lower motor neuron lesion (flaccid paralysis) with decreased deep tendon reflexes and muscle wasting; sensation intact

General Considerations

• Poliomyelitis virus, an enterovirus, is highly contagious through fecal-oral route, especially during the first week of infection

• There are three wild poliovirus serotypes, however, only wild poliovirus type 1 has remained endemic since 2012

• Pakistan, Afghanistan, and Nigeria remain the only countries with endemic poliovirus transmission since 2014

• In 2019, there were 29 cases of wild type polio in Afghanistan and 146 in Pakistan

• In 2020, there have been 2 cases of wild type polio in Afghanistan and 21 cases in Pakistan

• In 2019, there were 354 vaccine-derived polio cases, derived mostly from type 2 attenuated live oral poliovirus vaccine (OPV), reported in 17 countries

• In 2020, there have been 18 cases of vaccine-derived polio reported in 7 countries

• Cases of acute flaccid myelitis (formerly acute flaccid paralysis) resembling polio but not due to poliomyelitis virus are being reported

Symptoms and Signs

• At least 95% of infections are asymptomatic

• Patients who become symptomatic can present with abortive poliomyelitis, nonparalytic poliomyelitis, or paralytic poliomyelitis

  • Abortive poliomyelitis: minor illness with nonspecific symptoms, fever, headache, vomiting, diarrhea, constipation, and sore throat lasting 2–3 days

  • Nonparalytic poliomyelitis: In addition to the above symptoms, signs of meningeal irritation and muscle spasm occur in the absence of frank paralysis

  • Paralytic poliomyelitis: present during the febrile period over 2–3 days, is a flaccid asymmetric paralysis affecting mostly the proximal muscles of the lower extremities

    • Sensory loss is very rare

    • Can be divided into two forms that may coexist: (1) spinal poliomyelitis, involving the muscles innervated by the spinal nerves; and (2) bulbar poliomyelitis, involving the muscles supplied by the cranial nerves (especially nerves IX and X) and of the respiratory and vasomotor centers

• Post-polio syndrome

  • Constellation of symptoms that affect polio survivors and is not infectious

  • The syndrome presents with signs of chronic and new denervation

  • The most frequent symptoms are progressive muscle limbs paresis with muscle atrophy, with fasciculations and fibrillation during rest activity

• Acute flaccid myelitis

  • There is no evidence of poliomyelitis infection

  • Enteroviruses are isolated in some of these cases

Differential Diagnosis

• Acute inflammatory polyneuritis (Guillain-Barré syndrome)

• Japanese encephalitis virus infection

• West Nile virus infection

• Tick paralysis

• Acute flaccid myelitis

• The virus may be recovered from throat washings (early) and stools (early and late)

• PCR of washings, stool, or cerebrospinal fluid can also facilitate diagnosis

• Cerebrospinal findings

  • Normal or slightly increased pressure and protein

  • Glucose is not decreased

  • White blood cells usually < 500/mcL and are principally lymphocytes after the first 24 hours

  • Normal in 5% of patients

• Characteristic clinical symptoms and viral recovery from stools or neutralizing antibodies clinch the diagnosis

• In the acute phase of paralytic poliomyelitis, patients should be hospitalized

• In cases of respiratory weakness or paralysis, intensive care is needed

• Intensive physiotherapy may help recover some motor function with paralysis

• Attention to psychological disorders in long-standing disease is also important

• Immunodeficient individuals have prolonged excretion of poliovirus leading to virus circulation and threatening the polio eradication efforts

• Pocapavir, a capsid inhibitor antiviral agent

  • Was tested in healthy adults given monovalent OPV type 1

  • Was shown to be safe and effective in reducing the duration of viral excretion in stool

  • Resistance emerged in 44% of treated participants in this study

Prognosis

• The death-to-case ratio for paralytic polio ranges between 2% and 30%, depending on age

• Bulbar poliomyelitis carries a mortality rate of up to 75%

Prevention

• The inactive (Salk) parenteral vaccine is used in the United States for all four recommended doses (at ages 2 months, 4 months, 6–18 months, and at 4–6 years)

• Inactivated vaccine is also routinely used elsewhere in the developed world where one dose is often administered, although immunogenicity is improved with additional doses

• Routine immunization of adults in the United States is no longer recommended because of the low incidence of the disease

• Monovalent OPV type 2 (mOPV2) as well as the trivalent OPV are used for control in countries with vaccine-derived type 2 outbreaks

• Vaccination should be considered for

  • Adults not vaccinated within the prior decade who are exposed to poliomyelitis or who plan to travel to endemic areas

  • Adults engaged in high-risk activities (eg, laboratory workers handling stools)

When to Refer

• Any suspicious cases should be referred to public health authorities