Infectious Disease and Microbiology – Enterovirus Group

Overview

Enteroviruses are a major group of small, single-stranded RNA viruses within the family Picornaviridae. They have a worldwide distribution and commonly infect humans.

The enterovirus group includes polioviruses, coxsackieviruses, echoviruses, and several numbered enteroviruses. Different members can cause illnesses ranging from mild febrile disease to conjunctivitis, meningitis, encephalitis, myocarditis, hand-foot-and-mouth disease, and poliomyelitis-like neurologic syndromes.

Picornaviridae

Two major groups of Picornaviridae commonly associated with human disease are:

• Enteroviruses

• Rhinoviruses

Both are small RNA viruses, but their tissue tropism and clinical manifestations differ considerably.

Enterovirus Subgroups

Traditionally, the enterovirus group includes:

• Polioviruses – serotypes 1–3

• Coxsackievirus A – multiple serotypes

• Coxsackievirus B – multiple serotypes

• Echoviruses

• Numbered enteroviruses, including EV-A71 and EV-D68

Older classifications sometimes referred to hepatitis A virus as enterovirus 72, but hepatitis A virus is now classified in the genus Hepatovirus within Picornaviridae rather than as an enterovirus.

Microbiologic Characteristics

Enteroviruses are:

• Single-stranded RNA viruses

• Positive-sense RNA viruses

• Nonenveloped (naked)

• Icosahedral

Their lack of an envelope contributes to their ability to remain relatively stable in the environment.

Epidemiology

Enterovirus infections are common worldwide.

Transmission frequently occurs through the fecal–oral route, although some enteroviruses can also spread through respiratory secretions or direct contact with contaminated material.

Incubation Period

The incubation period varies considerably depending on the specific enterovirus and clinical syndrome.

For acute hemorrhagic conjunctivitis, the source describes a particularly short incubation period of:

12–72 hours

This short incubation can contribute to rapid spread during outbreaks.

Clinical Spectrum

Enteroviruses can cause a remarkably broad range of diseases, including:

• Febrile illness

• Skin and mucosal eruptions

• Hand-foot-and-mouth disease

• Herpangina

• Acute hemorrhagic conjunctivitis

• Aseptic meningitis

• Encephalitis

• Myocarditis and pericarditis

• Pleurodynia

• Poliomyelitis and poliomyelitis-like syndromes

• Severe neonatal infection

The clinical syndrome varies according to the specific virus and host.

Acute Hemorrhagic Conjunctivitis

Enterovirus 70 (EV-70) is classically associated with acute hemorrhagic conjunctivitis.

The illness has a rapid onset and can spread efficiently between individuals.

Clinical Features of Acute Hemorrhagic Conjunctivitis

Typical manifestations include:

• Acute eye pain or irritation

• Conjunctival redness

• Eyelid swelling

• Excessive tearing

• Foreign-body sensation

• Subconjunctival hemorrhage

The hemorrhagic appearance is a characteristic feature.

Enterovirus A71

Enterovirus A71 (EV-A71) is an important neurotropic enterovirus.

It can cause:

• Hand-foot-and-mouth disease

• Skin rash

• Meningitis

• Encephalitis

• Brainstem encephalitis

• Acute flaccid paralysis or a poliomyelitis-like syndrome

Young children can develop particularly severe neurologic disease.

Poliomyelitis-Like Syndrome

Some non-polio enteroviruses can affect motor neurons and produce acute flaccid weakness or paralysis resembling poliomyelitis.

Thus:

Acute flaccid paralysis does not automatically mean poliovirus infection.

Other enteroviruses should also be considered.

Meningitis and Encephalitis

Enteroviruses are important causes of aseptic meningitis.

Neurologic manifestations may include:

• Fever

• Headache

• Neck stiffness

• Photophobia

• Vomiting

When brain tissue is involved, patients may develop encephalitis, characterized by altered mental status, seizures, or other neurologic abnormalities.

Diagnosis

Traditional diagnostic methods include:

• Cell culture

• Serologic testing

Serology may provide supportive evidence in selected clinical situations.

Molecular Diagnosis

In modern clinical practice, RT-PCR and other nucleic-acid amplification tests are important methods for detecting enterovirus RNA.

Depending on the syndrome, testing may be performed on:

• Cerebrospinal fluid

• Respiratory specimens

• Stool

• Blood

• Vesicular or other lesion specimens

For suspected enteroviral meningitis, molecular detection from CSF can be particularly useful.

Treatment

Treatment is primarily:

Symptomatic and supportive

Management depends on the clinical syndrome and severity of infection.

Antiviral Therapy

The source states:

There is no effective specific antiviral treatment routinely available.

Supportive management may include hydration, analgesia, fever control, neurologic monitoring, and intensive care when severe CNS or cardiopulmonary complications occur.

Prevention

Good hygiene is important because enteroviruses can spread through contaminated hands, surfaces, respiratory secretions, and fecal material.

Preventive measures include:

• Frequent handwashing

• Appropriate sanitation

• Cleaning contaminated surfaces

• Avoiding close contact during contagious illness

• Avoiding sharing personal items

Conjunctivitis Prevention

During outbreaks of acute hemorrhagic conjunctivitis:

Do not share towels or other personal items that contact the eyes or face.

This helps prevent indirect transmission of the virus between individuals.

High-Yield Clinical Pattern – Enterovirus 70

Very short incubation of 12–72 hours

• ●

Rapid-onset conjunctivitis

• ●

Subconjunctival hemorrhage

→ Think Enterovirus 70

High-Yield Clinical Pattern – Enterovirus A71

Young child

• ●

Hand-foot-and-mouth disease or rash

• ●

Encephalitis or acute flaccid paralysis

→ Think Enterovirus A71

Exam Essentials

Group: Enterovirus

Family: Picornaviridae

Genome: Positive-sense single-stranded RNA

Envelope: Absent (naked)

Capsid: Icosahedral

Distribution: Worldwide

Frequency: Common

Major transmission: Fecal–oral; some also spread through respiratory/contact routes

EV-70: Acute hemorrhagic conjunctivitis

EV-70 incubation: 12–72 hours

EV-A71: Hand-foot-and-mouth disease + neurologic disease

Neurologic manifestations: Meningitis, encephalitis, acute flaccid paralysis

Diagnosis: Molecular testing, with culture and serology in selected settings

Treatment: Supportive

Specific routine antiviral treatment: None

Conjunctivitis prevention: Avoid sharing towels and other potentially contaminated personal items

Historical terminology: Hepatitis A was formerly called enterovirus 72 but is now classified as a Hepatovirus

Key clinical pearl: Remember EV-70 → acute hemorrhagic conjunctivitis, while EV-A71 → hand-foot-and-mouth disease with potential severe neurologic complications such as encephalitis and poliomyelitis-like acute flaccid paralysis.