Enteroviruses 

Nonpolio enteroviruses are responsible for significant and frequent illnesses in infants and children and result in protean clinical manifestations. 

Etiology:

• The nonpolio Enteroviruses are positive strand RNA viruses. 

Life cycle of the virus

Clinical Manifestations:

• Common presentation

  • Incubation period is one week

  • After initial replication in gut the virus is spread to the target organ by viremia.

  • The most common presentation is nonspecific febrile illness

  • Most patients present with papulovescicular lesions and mild fever

    • The maculopapular eruptions may also be evident on the buttocks, extremities, and face, more often in young children.

    • The lesion may last three to four days.

• Who is at risk

  • Infants and children

  • Neonates who acquire infection without maternal antibody are at risk of severe disease with a high mortality rate. 

  • Immunocompromised patients with humoral deficiencies can have persistent central nervous system infections lasting for several months or more.

  • Adults can get the infection if they do not have pre-existing immunity.

    • Disease is no more severe in adults than in children.

• Clinical  Manifestations can include the following:

  • respiratory-- common cold, pharyngitis, herpangina, stomatitis, pneumonia, and pleurodynia

  • skin--exanthem

  • neurologic--aseptic meningitis, encephalitis, and paralysis

  • gastrointestinal--vomiting, diarrhea, abdominal pain, and hepatitis

  • eye--acute hemorrhagic conjunctivitis

  • heart--myopericarditis

• Viral Associations

  • coxsackievirus 

    • A16 and enterovirus 71:  hand, foot, and mouth syndrome

    • A24 variant and enterovirus 70: acute hemorrhagic conjunctivitis

    • B1 to B5:  pleurodynia and myopericarditis

  • enterovirus 71: encephalitis and polio-like paralysis

  • echovirus 9: petechial exanthem and meningitis

• Recurrence

  • Type specific immunity is generated, providing protection from re-infection with that specific serotype of enterovirus.

  • However there are 64 serotypes of enterovirus and little if any cross-protection.

Epidemiology:

• Transmission

  • Enterovirus infections are common and are spread by fecaloral and respiratory routes and from mother to infant in the peripartum period. Fecal viral shedding can continue for several weeks (upto 3 months) after onset of infection, while respiratory tract shedding usually is limited to a week or less. Viral shedding can occur without signs of clinical illness.

  • Enteroviruses may survive on environmental surfaces for periods long enough to allow transmission from fomites.

• Prevalence

  • Infections and clinical attack rates typically are highest in young children, and infections occur more frequently in lower socioeconomic groups, in tropical areas, and when hygiene is poor. 

  • In temperate climates, enteroviral infections are most common in the summer and early fall, but seasonal patterns are less evident in the tropics. 

• The usual incubation period is 3 to 6 days

Diagnostic Tests:

Specimens providing the highest rate of viral isolation are those obtained from the 

• throat, stool, and rectal swabs.

• from any sites of clinical involvement, such as cerebrospinal fluid (CSF). 

• may be recovered from blood during the acute febrile phase 

• rarely from biopsy material. 

• Viral isolation from any specimen except feces usually can be considered causally related to the patient's illness. 

  • The virus can be cultured from the cutaneous vesicles or oral lesions and causes lytic cytopathologic effect (CPE) in cultured cells. Immunofluorescence can then be used to type the virus (research and epidemiological purposes).

  • Some asymptomatic infected persons may shed virus in feces for as long as 6 to 12 weeks. 

•  Polymerase chain reaction testing for the presence of enterovirus RNA in CSF, which is available in a few research laboratories, is more sensitive than viral isolation.

•  Serum samples for antibody testing can be collected at the onset of illness and 4 weeks later and stored frozen. 

  • The demonstration of a rise in titer of virus specific neutralizing antibody can be used to confirm infection, particularly when the specific virus has been identified previously during a community outbreak. 

Treatment:

• No specific therapy is available, although an antiviral agent, pleconaril, is undergoing clinical evaluation in immunocompetent infants with aseptic meningitis and in immunodeficient children. 

• Immune Globulin Intravenous containing high antibody titer to the infecting virus 

  • For chronic enteroviral meningoencephalitis in an immunodeficient patient, may be beneficial for treatment of persistent enterovirus infection. 

  • Immune Globulin Intravenous also has been used in life-threatening neonatal infections

• Isolation of the Hospitalized Patient:

  • In addition to standard precautions, contact precautions are indicated for infants and young children for the duration of hospitalization.

  • Particular attention should be given to hand washing and personal hygiene, especially after diaper changing.