General Characteristics and Epidemiology
General features of Echovirus
- Echoviruses (enteric cytopathic human orphan viruses) represent strains of various species within:
- Family: Picornaviridae
- Genus: Enterovirus
- RNA virus:
- Single stranded
- Positive sense
- Functions as mRNA
- Diameter: 20–30 nm
- Icosahedral symmetry
- Lacks a lipid envelope
- Acid resistant
Clinically relevant species
There are approximately 29 recognized Echovirus serotypes:
- Worldwide distribution
- Peak incidence: summer and early fall
- Affects more children than adults
- Children: boys > girls
- Adolescents and adults: women > men
Humans are the only reservoir.
- Fecal-oral route (most common)
- Respiratory aerosols
Outbreaks are common in:
- Daycare centers
- Oral entry of the virus → replication in the pharyngeal and GI mucosal and lymphatic tissues
- Asymptomatic viremia → reticuloendothelial system, including:
- Distant lymph nodes
- Bone marrow
- Replication occurs → secondary spread to:
Most infections are subclinical (50%‒80% are asymptomatic), and the clinical presentation can vary from mild to lethal.
Patients may have symptoms of an upper respiratory tract infection:
Cutaneous and mucosal disease
- Vesicular lesions of the tonsillar fossa and soft palate
Exanthems may be:
- Nuchal rigidity
- Personality changes
Other rare, neurologic manifestations:
- Muscle weakness or paralysis
- Guillain-Barré syndrome
- Transverse myelitis
Myopericarditis may occur in a minority of patients.
- Chest pain
Neonates can present with a wide range of presentations, from mild to life-threatening.
- Respiratory distress
- Multi-organ failure
Diagnosis and Management
Most infections are diagnosed based on clinical presentation. A laboratory diagnosis may be needed in severe infections.
- Viral culture
- Serology has limited value.
Most echovirus infections are self-limiting and the management is largely supportive. Unproven therapeutic options that can be considered for severe disease or immunocompromised patients may include:
- IV immunoglobulin (IVIG)
- Rarely used
- Not FDA approved
- Handwashing (alcohol-based hand sanitizers may not be effective)
- Maintaining clean living conditions
- Minimizing contact with infected individuals
Comparison of Enteroviruses
URTI: upper respiratory tract infection
- Respiratory syncytial virus infection: an infection of the lower respiratory tract caused by an enveloped ssRNA virus. Respiratory syncytial virus infection presents with fever, cough, wheezing, tachypnea, and crackles. The diagnosis is made clinically. Management is supportive.
- Rhinovirus infection: an infection caused by an acid-labile, positive-sense RNA virus of the Picornaviridae family. As rhinoviruses are inactivated by gastric acid, they can only affect the nasal mucosa and conjunctiva, causing edema of the subepithelial tissues. A rhinovirus infection presents as a “common cold” with mild upper respiratory symptoms. Diagnosis is clinical, and the disease is typically minor and self-limiting. Management is supportive.
- Infectious mononucleosis: a disease caused by the EBV that is characterized by fever, fatigue, lymphadenopathy, and pharyngitis. Complications can include peripheral neuropathy, viral meningitis, Guillain-Barré syndrome, and myocarditis. The diagnosis is based on clinical features and testing, such as a positive heterophile antibody test or serology. Management is supportive.
- Bacterial meningitis: an acute infection of the meninges. Patients present with headache, fever, nuchal rigidity, and rapid clinical deterioration. A lumbar puncture is performed to make the diagnosis. Unlike the findings in aseptic meningitis, CSF studies show turbid fluid, low glucose levels, and high WBC count with neutrophil predominance. Gram stain and culture are used to determine the causative bacteria. Treatment includes antibiotics and corticosteroids.
- Adenovirus infection: a non-enveloped double-stranded DNA virus that typically causes mild respiratory infections; conjunctivitis, atypical pneumonia, gastroenteritis, meningoencephalitis, and myocarditis can also occur. The diagnosis is typically clinical, but a PCR test may be performed to confirm the diagnosis of severe disease. Management is supportive.
- West Nile virus infection: an infection by a flavivirus. The majority of patients will be asymptomatic or have a headache, myalgias and arthralgias, vomiting, diarrhea, or a rash. A small proportion of patients develop encephalitis, meningitis, or flaccid paralysis. The diagnosis can be made using serology, PCR, and viral cultures, which can differentiate a West Nile virus infection from an echovirus infection. Management is supportive.
- Lyme disease: a tick-borne infection caused by the gram-negative spirochete, Borrelia burgdorferi. The presentation of Lyme disease can vary depending on the stage of the disease and may include the characteristic erythema migrans rash (not present in an echovirus infection). Neurological, cardiac, ocular, and joint manifestations are also common in later stages. Diagnosis of Lyme disease relies on clinical findings and tick exposure, and is supported by serological testing. Antibiotics are used for treatment.
- Ehrlichiosis and anaplasmosis: tick-borne infections caused by Ehrlichia chaffeensis and Anaplasmosis phagocytophilum, respectively. Symptoms of ehrlichiosis and anaplasmosis include fever, headache, and malaise. Disseminated intravascular coagulation, multiorgan failure, and coma can also occur with severe disease. The diagnosis is made using PCR. Treatment of both diseases is with doxycycline.
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