Updated: Jul 29, 2008
Echoviruses (EVs) are RNA viruses of the genus Enterovirus and the family Picornaviridae. EVs were first isolated from the feces of asymptomatic children early in the 1950s, soon after the development of cell culture techniques. EVs cause cytopathic effects in primate cell cultures, although not initially associated with any disease condition. These orphan viruses were initially termed ECHO, an acronym for enteric cytopathic human orphan virus, which was later simplified to echovirus.
A committee sponsored by the National Foundation for Infantile Paralysis categorized EVs and other enteroviruses (ie, coxsackievirus group A and group B, polioviruses) together in 1957. They are grouped together and distinguished from other viruses on the basis of physicochemical characteristics and because they share common epidemiology, clinical manifestations, and pathogenesis. Enterovirus groups are differentiated based on host specificity. To date, 67 serotypes of enterovirus have been identified, 32 of which belong to the echovirus group.
EVs cause a wide range of common and uncommon clinical presentations. These agents and other members of the Enterovirus group are among the leading causes of acute febrile illness in infants and young children; they are the most common cause of aseptic meningitis. Infection in the first 2 weeks of life is particularly troublesome because it can cause severe systemic disease and is associated with high fatality rates. Another significant concern with enteroviral infections is that they can mimic symptoms caused by other common bacteria and viral infections; thus, enteroviral infections are often treated with therapies aimed for other infections.
EVs are small, measuring 24-30 nanometers (nm) under electron microscopy. They are composed of a naked protein capsid, constituting about 75% of the particle and enclosing a dense central core of single-stranded RNA. This RNA is approximately 7.5 kilobase (kb) long and contains an RNA replicase, viral-coded proteases, a single polyprotein that is responsible for forming structural polypeptides, and other proteins necessary for cellular replication. All EVs contain polypeptide chains (eg, virus protein 1 [VP1], virus protein 4 [VP4]). These structural proteins are important to determine host range and tropism, and they play a crucial role in delivering the RNA genome into the cytoplasm of new host cells.
Although EVs originally were classified into 34 serotypes, EV-10 later was reclassified as a reovirus and EV-28 as rhinovirus type 1; EV-9 now is considered the same as coxsackievirus A23.
At least 2 cellular receptors for EV have been identified: a subunit of the integrin molecule VLA-2 that binds types 1 and 8, and a complement regulatory protein (ie, a decay accelerating factor) that binds types 6, 7, 12, and 21.
Some viral replication occurs in the nasopharynx after exposure, with spread to regional lymph nodes. However, most inoculum is swallowed and reaches the lower GI tract, where the virus presumably binds to specific receptors on enterocytes. The virus traverses the intestinal epithelium, probably undergoing replication in the process but without causing any cellular effects, and reaches the Peyer patches in the lamina propria mucosae. Here, the virus undergoes substantial multiplication. A minor viremia develops on about the third day, seeding many secondary infection sites, including the CNS, liver, spleen, bone marrow, heart, and lungs. Additional replication at these sites causes a major viremia that coincides with onset of clinical disease, usually 4-6 days after exposure. The delayed appearance of CNS disease symptoms suggests viral spread can develop during both the minor and the major viremia.
Enteroviruses can infect all tissues of the human body. The tropism of each virus for certain tissues is not well understood and is neither unique nor specific. Infections involving a single serotype may vary widely in their presentation; multiple serotypes can produce the same clinical syndrome.
The incubation period for EV is difficult to establish because both symptomatic and healthy individuals spread the virus. Incubation is believed to range between 2 days and 2 weeks. EV is communicable over a long period of time. The virus can be shed from the upper respiratory tract for 1-3 weeks and in stools for more than 8 weeks after primary infection.
Several studies confirm enteroviruses account for more than 50% of spring and fall emergency department visits by infants and young children for fever without a source. EV infections only sporadically develop in other seasons. In addition to this seasonality, EV types vary strikingly in their contribution to human disease. Some EVs remain endemic in patterns that vary from area to area each year in the United States. Other serotypes (eg, EV-9, EV-11, EV-30) can cause widespread outbreaks in which the responsible strain can account for more than 90% of all isolated strains of enterovirus.
Infections by this group of viruses are most prevalent among lower socioeconomic groups, a fact easily explained by overcrowded living conditions and poor hygiene.
EV infections occur in all human populations. Transmission and infection occur throughout the year in the tropics and predominantly during summer and fall in temperate regions, with sporadic cases in other seasons. A few epidemics have been nearly global, such as one caused by EV-9 at the end of the 1950s and another by EV-11 in 1979 and 1980. More recently, an outbreak of EV-13 and EV-30 was reported in Germany,1 and outbreaks of EV-13 were reported in Lithuania and Israel.2,3 An outbreak of EV-11 has also been reported in neonates in Taiwan.4 Particular serotypes are endemic or epidemic for unknown reasons. One hypothesis is that some epidemic strains such as EV-9 may spread rapidly in a "critical mass" of susceptible patients necessary for continuous transmission, whereas endemic strains may not be as contagious.
EV infections during the first 2 weeks of life can cause severe systemic disease associated with high fatality rates. EV and other enteroviruses account for 10-20% of documented viral causes of encephalitis. Neonates with disseminated encephalitis have a poor prognosis and many die. Infant death rates from perinatal EV infection are unknown, although some studies report high numbers. Neonatal mortality is usually caused by either overwhelming liver failure or myocarditis, rather than CNS involvement.
Children and older patients with disseminated encephalitis have a better prognosis, but fatalities occasionally occur. Acute myopericarditis, resulting from the well-established tropism of enterovirus for the heart, can be fatal in approximately 5% of cases, although most patients recover without major sequelae.
For unknown reasons, forms of EV disease such as meningitis and neonatal sepsis are far more common among male patients.
Although EV infections can occur in all age groups, incidence inversely relates to age; specific antibodies directly increase with time. Several studies performed during epidemics and for surveillance show that infants become infected at significantly higher rates than older children and adults.
Because echovirus (EV) has been found in the stools of healthy individuals, most children with EV and other enteroviral infections are assumed to be asymptomatic. Finding the virus in the stools of healthy individuals, however, may be misleading because enterovirus can be excreted in feces for a long time, and no clear indication exists of what happened during the initial infection. Patients may have symptoms with infection, but the symptoms may be trivial and not recognized.
EV causes a remarkable range of diseases. Benign forms of disease are well recognized by clinicians (eg, nonspecific exanthems, herpangina) and do not warrant major diagnostic or therapeutic actions. Severe forms of disease, such as meningitis, encephalitis, neonatal sepsis, myocarditis, and chronic infection with meningoencephalitis in patients with altered immunity, are strong reasons for concern.
Overcrowded conditions and poor hygiene easily explain the high prevalence of EV infections among lower socioeconomic groups.
Neonatal Sepsis
Bacterial sepsis
Bacterial meningitis
Neonatal herpes simplex infection
Herpes simplex virus encephalitis
Arbovirus encephalitis
Fever without localizing signs
Viral exanthems
Pharyngoconjunctival fever
Until recently, the criterion standard laboratory procedure to diagnose echovirus (EV) and other enterovirus infections was to isolate the virus in cell culture. An etiologic diagnosis is confirmed when virus is isolated from blood, CSF, tissue, or pericardial fluid. EV can also be isolated from stool or oropharynx, although these findings are less indicative of disease because asymptomatic shedding from these sites can occur for several weeks after acute infection.
No antiviral therapy has been available except IVIG therapy, which reportedly has some success in patients who are immunocompromised and have persistent enterovirus infections. The role of IVIG therapy for acute infections is unproven. A study evaluating its use in enteroviral infection in neonates failed to demonstrate a clear benefit. Another study evaluating the use of IVIG in 21 patients with myocarditis showed improved left ventricular function and survival when compared with 25 control patients. However, additional studies are needed.
Corticosteroid use to treat viral myopericarditis remains controversial at best. Several antiviral agents have in vitro activity against a broad range of enterovirus types, and several clinical trials have been conducted on their use.
Hauri AM, Schimmelpfennig M, Walter-Domes M, et al. An outbreak of viral meningitis associated with a public swimming pond. Epidemiol Infect. 2005;133:291-8. [Medline].
Narkeviciute I, Vaiciuniene D. Outbreak of echovirus 13 infection among Lithuanian children. Clin Microbiol Infect. 2004;10:1023-5. [Medline].
Somekh E, Cesar K, Handsher R, et al. An outbreak of echovirus 13 meningitis in Central Israel. Epidemiol Infect. 2003;130:257-62. [Medline].
Chen JH, Chiu NC, Chang JC, et al. A neonatal echovirus 11 outbreak in an obstetric clinic. J Microbiol Immunol Infect. 2005;38:332-7. [Medline].
Hamilton MS, Jackson MA, Abel D. Clinical utility of polymerase chain reaction testing for enteroviral meningitis. Pediatr Infect Dis J. Jun 1999;18(6):533-7. [Medline].
Sawyer MH, Holland D, Aintablian N, et al. Diagnosis of enteroviral central nervous system infection by polymerase chain reaction during a large community outbreak. Pediatr Infect Dis J. Mar 1994;13(3):177-82. [Medline].
Schlesinger Y, Sawyer MH, Storch GA. Enteroviral meningitis in infancy: potential role for polymerase chain reaction in patient management. Pediatrics. Aug 1994;94(2 Pt 1):157-62. [Medline].
Pevear DC, Tull TM, Seipel ME, Groarke JM. Activity of pleconaril against enteroviruses. Antimicrob Agents Chemother. Sep 1999;43(9):2109-15. [Medline].
National Institutes of Health. Effects of Pleconaril Nasal Spray on Common Cold Symptoms and Asthma Exacerbations Following Rhinovirus Exposure (Study P04295AM2). Clinical Trials.gov. Available at http://www.clinicaltrials.gov/ct/gui/show/NCT00394914. Accessed May 9, 2008.
Abzug MJ, Cloud G, Bradley J, et al. Double blind placebo-controlled trial of pleconaril in infants with enterovirus meningitis. Pediatr Infect Dis J. 2003;22:335-41. [Medline].
Abzug MJ. Presentation, diagnosis, and management of enterovirus infections in neonates. Paediatr Drugs. 2004;6:1-10. [Medline].
Abzug MJ, Levin MJ, Rotbart HA. Profile of enterovirus disease in the first two weeks of life. Pediatr Infect Dis J. Oct 1993;12(10):820-4. [Medline].
Cherry J. Enteroviruses. In: Remington J, Klein J, eds. Infectious Diseases of the Fetus and Newborn Infant. 1995. 4th ed. Philadelphia, Pa: WB Saunders Co; 404-46.
Cherry J. Enteroviruses: Coxsackieviruses, Echoviruses and Polioviruses. In: Feigin R, Cherry J, eds. Textbook of Pediatric Infectious Diseases. 4th ed. Philadelphia, PA: WB Saunders Co; 1998:1787-839.
Dagan R. Nonpolio enteroviruses and the febrile young infant: epidemiologic, clinical and diagnostic aspects. Pediatr Infect Dis J. Jan 1996;15(1):67-71. [Medline].
Estrada B. Enteroviral Meningitis: Time for PCR?. Infect Med. 1999;16:493.
Frisk G, Tuvemo T. Enterovirus infection with beta-cell tropic strains are frequent in siblings of children diagnosed with type 1 diabetes children and in association with elevated levels of GAD65 antibodies. J Med Virol. 2004;73:450-9. [Medline].
Joki-Korpela P, Hyypia T. Diagnosis and epidemiology of echovirus 22 infections. Clin Infect Dis. Jul 1998;27(1):129-36. [Medline].
Krajden S, Middleton P. Enterovirus Infections in the Neonate. Clin Pediatr. 1982;22:87-92.
Modlin J. Coxsackieviruses, echoviruses and newer enteroviruses. In: Mandell G, Bennett J, Dolin R. Douglas and Bennett's Principles and Practice of Infectious Diseases. 4th ed. New York, NY: Churchill Livingstone; 1995:1620-36.
Modlin J. Enteroviruses: Coxsackieviruses, echoviruses, and newer enterovirus. In: Long S, Pickering L, Prober C, eds. Principles and Practice of Pediatric. ed. 1997.
Modlin JF. Perinatal echovirus infection: insights from a literature review of 61 cases of serious infection and 16 outbreaks in nurseries. Rev Infect Dis. Nov-Dec 1986;8(6):918-26. [Medline].
Modlin JF. Update on enterovirus infections in infants and children. Adv Pediatr Infect Dis. 1996;12:155-80. [Medline].
Onishi N, Hosoya M, Sato K, et al. First report of an outbreak of aseptic meningitis caused by echovirus type 13 in Japan. Pediatr Int. Aug 2003;45(4):494-6. [Medline].
Paananen A, Ylipaasto P, Rieder E, et al. Molecular and biological analysis of echovirus 9 strain isolated from a diabetic child. J Med Virol. 2003;69:529-37. [Medline].
Pichichero ME, McLinn S, Rotbart HA, et al. Clinical and economic impact of enterovirus illness in private pediatric practice. Pediatrics. Nov 1998;102(5):1126-34. [Medline].
Rabkin CS, Telzak EE, Ho MS, et al. Outbreak of echovirus 11 infection in hospitalized neonates. Pediatr Infect Dis J. Mar 1988;7(3):186-90. [Medline].
Rotbart HA. Enteroviral infections of the central nervous system. Clin Infect Dis. Apr 1995;20(4):971-81. [Medline].
Sawyer MH. Enterovirus infections: diagnosis and treatment. Pediatr Infect Dis J. Dec 1999;18(12):1033-9; quiz 1040. [Medline].
Shah SS, Gallagher PG. Neonatal sepsis due to echovirus 18 infection. J Perinat Med. 1997;25(4):381-4. [Medline].
Verboon-Maciolek MA, Swanink CM, Krediet TG, et al. Severe neonatal echovirus 20 infection characterized by hepatic failure. Pediatr Infect Dis J. May 1997;16(5):524-7. [Medline].
echovirus, ECHO virus, ECHOvirus, EV, enteric cytopathic human orphan virus, aseptic meningitis, coxsackievirus, rhinovirus, viremia, disseminated encephalitis, liver failure, myocarditis, neonatal sepsis, bacterial sepsis, echoviral meningitis, herpes simplex encephalitis, poliomyelitis, pleurodynia, pleural inflammation, pneumonia, pleural effusion, appendicitis, peritonitis, upper respiratory infection, pericardial friction rub, congestive heart failure, CHF, respiratory distress, hepatic necrosis, disseminated intravascular coagulation, bronchitis, bronchiolitis
Jorge M Quinonez, MD, Medical Director of Pediatrics, Chief Medical Officer, Family Health Centers of South West Florida, Inc
Jorge M Quinonez, MD is a member of the following medical societies: American Academy of Pediatrics and Infectious Diseases Society of America
Disclosure: Nothing to disclose.
Leonard R Krilov, MD, Chief of Pediatric Infectious Diseases, Vice Chair, Department of Pediatrics, Professor of Pediatrics, Winthrop University Hospital
Leonard R Krilov, MD is a member of the following medical societies: American Academy of Pediatrics, American Pediatric Society, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, and Society for Pediatric Research
Disclosure: Medimmune Grant/research funds Cliinical trials; Medimmune Honoraria Speaking and teaching; Medimmune Consulting fee Consulting
Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine.com, Inc
Disclosure: Pfizer Inc Stock Investment from broker recommendation; Avanir Pharma Stock Investment from broker recommendation
Joseph Domachowske, MD, Professor of Pediatrics, Microbiology and Immunology, Department of Pediatrics, Division of Infectious Diseases, State University of New York-Upstate Medical University
Joseph Domachowske, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American Society for Microbiology, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, and Phi Beta Kappa
Disclosure: Nothing to disclose.
Robert W Tolan Jr, MD, Chief, Division of Allergy, Immunology and Infectious Diseases, The Children's Hospital at Saint Peter's University Hospital; Clinical Associate Professor of Pediatrics, Drexel University College of Medicine
Robert W Tolan Jr, MD is a member of the following medical societies: American Academy of Pediatrics, American Medical Association, American Society for Microbiology, American Society of Tropical Medicine and Hygiene, Infectious Diseases Society of America, Pediatric Infectious Diseases Society, Phi Beta Kappa, and Physicians for Social Responsibility
Disclosure: GlaxoSmithKline Honoraria Speaking and teaching; MedImmune Honoraria Consulting; MedImmune Honoraria Speaking and teaching; Merck Honoraria Speaking and teaching; Novartis Honoraria Speaking and teaching; sanofi pasteur Grant/research funds Unrestricted research grant; sanofi pasteur Consulting; sanofi pasteur Honoraria Speaking and teaching; Tap Honoraria Speaking and teaching
Russell W Steele, MD, Head, Division of Pediatric Infectious Diseases, Ochsner Children's Health Center; Clinical Professor, Department of Pediatrics, Tulane University School of Medicine
Russell W Steele, MD is a member of the following medical societies: American Academy of Pediatrics, American Association of Immunologists, American Pediatric Society, American Society for Microbiology, Infectious Diseases Society of America, Louisiana State Medical Society, Pediatric Infectious Diseases Society, Society for Pediatric Research, and Southern Medical Association
Disclosure: None None None
© 1994-
by Medscape.
All Rights Reserved
(http://www.medscape.com/public/copyright)