Poliovirus

After an incubation period of 3-6 days, ∼5% of pts present with a minor illness (abortive poliomyelitis) that is characterized by fever, malaise, sore throat, myalgias, and headache and that usually resolves within 3 days.

• Asymptomatic infection: >90% of all infections
• Aseptic meningitis (nonparalytic poliomyelitis): occurs in ∼1% of pts. Examination of CSF reveals normal glucose and protein concentrations and lymphocytic pleocytosis (with PMNs sometimes predominating early).
• Paralytic disease: the least common form, presenting ≥1 day after aseptic meningitis as severe back, neck, and muscle pain as well as gradually developing motor weakness
  • The weakness is usually asymmetric and proximal and is most common in the legs. The arms and the abdominal, thoracic, and bulbar muscles are also frequently involved.
  • Paralysis generally occurs only during the febrile phase.
  • Physical examination reveals weakness, fasciculations, decreased muscle tone, and reduced or absent reflexes in affected areas; hyperreflexia may precede the loss of reflexes. Bulbar paralysis is associated with dysphagia, difficulty handling secretions, or dysphonia.
  • Respiratory insufficiency due to aspiration or neurologic involvement may develop. Severe medullary infection may lead to circulatory collapse.
  • Most pts recover some function, but around two-thirds have residual neurologic sequelae.
• Vaccine-associated poliomyelitis: The risk of acquiring poliomyelitis after vaccination with the live oral vaccine is estimated to be 1 case per 2.5 million doses and is ∼2000 times higher among immunodeficient persons, especially pts with hypo- or agammaglobulinemia.
• Postpolio syndrome: new weakness 20-40 years after poliomyelitis. Onset is insidious, progression is slow, and plateau periods can last 1-10 years.

Other Enteroviruses

In the United States, 5-10 million cases of symptomatic enteroviral disease other than poliomyelitis occur each year. More than 50% of nonpoliovirus enterovirus infections are subclinical.

• Nonspecific febrile illness (summer grippe): Pts present with acute-onset fever, malaise, and headache, with occasional upper respiratory symptoms.
  • Disease resolves within a week.
  • Disease frequently occurs during the summer and early fall.
• Generalized disease of the newborn: Neonates, typically within the first week of life, present with an illness resembling bacterial sepsis, with fever, irritability, and lethargy.
  • Myocarditis, hypotension, hepatitis, DIC, meningitis, and pneumonia are complications.
  • A history of a recent flu-like illness in the mother should prompt consideration of this disease.
• Aseptic meningitis and encephalitis: Enteroviruses cause 90% of cases of aseptic meningitis among children and young adults in which an etiologic agent can be identified; 10-35% of viral encephalitis cases are due to enteroviruses.
  • Pts have an acute onset of fever, chills, headache, photophobia, nausea, and vomiting, with meningismus on examination. Diarrhea, rashes, myalgias, pleurodynia, myocarditis, and herpangina may occur. Encephalitis is much less common and is usually mild, with an excellent prognosis in healthy hosts.
  • CSF examination reveals pleocytosis, with PMNs sometimes predominating early but a shift to lymphocyte predominance within 24 h. Total cell counts usually do not exceed 1000/µL. CSF glucose and protein levels are typically normal.
  • Symptoms resolve within 1 week, but CSF abnormalities persist longer.
• Pleurodynia (Bornholm disease): Pts have an acute onset of fever associated with spasms of pleuritic chest pain (more common among adults) or upper abdominal pain (more common among children) that typically last 15-30 min. Fever subsides when pain resolves.
  • Coxsackievirus B is the most common cause.
  • Disease lasts for a few days and can be treated with NSAIDs and heat application to the affected muscles.
• Myocarditis and pericarditis: Enteroviruses (e.g., coxsackievirus B) cause up to one-third of cases of acute myocarditis. Pts have upper respiratory symptoms followed by fever, chest pain, dyspnea, arrhythmias, and occasionally heart failure.
  • Disease occurs most often in newborns (who are most severely ill), adolescents, and young adults.
  • A pericardial friction rub, ST-segment and T-wave abnormalities on electrocardiography, and elevated serum levels of myocardial enzymes can be present.
  • Up to 10% of pts develop chronic dilated cardiomyopathy.
• Exanthems: Enterovirus infection is the leading cause of exanthems among children in the summer and fall. Echoviruses 9 and 16 are common causes.
• Hand-foot-and-mouth disease: generally due to coxsackievirus A16 and enterovirus 71. Pts present with fever, anorexia, and malaise, which are followed by sore throat and vesicles on the buccal mucosa, tongue, and dorsum or palms of the hands and occasionally on the palate, uvula, tonsillar pillars, or feet.
  • The disease is highly infectious, with attack rates of almost 100% among young children. Symptoms resolve within a week.
  • Epidemics of enterovirus 71 infection occurred in Taiwan in 1998 and have occurred annually in China since 2008, with hundreds of thousands of cases and hundreds of deaths each year. These epidemics were associated with CNS disease (e.g., brain-stem encephalitis, seizures), myocarditis, and pulmonary hemorrhage. Deaths occurred primarily among children ≤5 years old.
• Herpangina: usually caused by coxsackievirus A infection. Pts develop fever, sore throat, odynophagia, and grayish-white papulovesicular lesions on an erythematous base that ulcerate and are concentrated in the posterior portion of the mouth.
  • Lesions can persist for weeks.
  • In contrast to herpes simplex stomatitis, enteroviral herpangina is not associated with gingivitis.
• Acute hemorrhagic conjunctivitis: associated with enterovirus 70 and coxsackievirus A24. Pts experience an acute onset of severe eye pain, blurred vision, photophobia, and watery eye discharge; edema, chemosis, and subconjunctival hemorrhage are evident. Symptoms resolve within 10 days.