Description, Causes and Risk Factors:
A large and diverse group of viruses (family Picornaviridae) that includes poliovirus types 1 to 3, Coxsackievirus A and B, echoviruses, and the enteroviruses identified since 1969 and assigned type numbers. They are transient inhabitants of the alimentary canal and are stable at low pH. Enteroviruses are so named because they reproduce initially in the gastrointestinal tract after infection occurs. Despite this, they usually do not lead to intestinal symptoms; rather it is their spread to organs, such as the nervous system, heart, skin, and others that causes disease.
Enterovirus infections are second only to the “common cold.” It has been estimated that at least 10 million to 15 million persons in the US develop some sort of enteroviral illness each year.
Anyone can become infected and ill with these viruses. Infants, children and adolescents are more likely to become ill than are adults. Adults are more likely to be immune to specific enteroviruses than are younger persons.
The incubation period for most enteroviral infections ranges from 3 to 10 days. The virus enters the host via the oral cavity and/or respiratory tract, then invades and replicates in the upper respiratory tract and small intestine, with a predilection for lymphoid tissues in these regions (Peyer patches, mesenteric nodes, tonsils, and cervical nodes). Virus then enters the bloodstream, resulting in a minor viremia and dissemination to a variety of target organs, including the central nervous system (CNS), heart, liver, pancreas, adrenal glands, skin, and mucous membranes. A major viremia results from viral replication at and dissemination from these secondary sites, which provide additional opportunities for seeding the CNS. The minor and major viremia may correlate with the biphasic appearance of fever and symptoms commonly described in enteroviral infection.
Transmission may occur if an infected person coughs or sneezes directly in the face of another person. These viruses can be transmitted by contact with feces, such as when persons changing diapers of infants and toddlers do not wash their hands thoroughly. Persons with no symptoms of illness who are infected with an enterovirus can infect other persons who may or may not become ill after they become infected. Enteroviral infections occur primarily during the summer and fall months.
The immune response in enteroviral infections involves an early immunoglobulin M (IgM) antibody response at 7 to 10 days, followed by a rise in immunoglobulin G (IgG) and intestinal IgA neutralizing antibodies. There is relative immunity to reinfection with the same serotype, but if reinfection does occur, the symptoms are ameliorated and the illness may be subclinical.
Symptoms of nonpolio enteroviral syndromes are usually nonspecific. Rarely the heart and brain are affected, as in myocarditis, pericarditis, and encephalitis.
The other symptoms of the enteroviral may include:
Nausea and vomiting.
Fever and chills.
Enteroviral infection usually is diagnosed clinically without isolationand identification of the specificvirus. Factors that aid in diagnosisinclude seasonality, knowledge ofexposure, and characteristic constellation of physical findings andsymptoms. In certain clinical situations, such as meningitis or neonataldisease, isolation and/or identification of the virus may be indicated.Laboratory methods for diagnosing enterovirus infections includecell culture, serology, and newlydeveloped PCR techniques.
Isolation of enterovirus from specimens using appropriate cultured cell linesis often possible within 2 or 3 days and remains a very sensitivemethod for detecting these viruses.The best specimens for isolation of virus are, in order of preference,stool specimens or rectal swabs, throat swabs or washings, andcerebrospinal fluid.
Culture, or growing the organism outside of the body, is helpful only when obtained from areas that tend to indicate recent infection, such as from swollen joints, cerebrospinal fluid, or blood. Cultures from other areas, such as the throat, can be misleading. This is because the virus may remain for long periods of time in places with a large amount of lymphatic tissue. As a rule, cultures done early in the illness are more likely to identify the virus.
New techniques that involve identification of viral genetic material (PCR) are useful in certain cases, but are not indicated for routine testing.
Enterovirus is capable of attacking many different organs and producing a variety of symptoms. Most infections are mild and improve without complications, requiring no specific therapy. When the virus attacks critical organs however, such as the heart, respiratory muscles, nervous system, etc., specialized care is often needed.
No effective antiviral therapy currently is available for enteroviral infections; treatment is symptomatic and supportive. Corticosteroids have been of some benefit in the treatment of myocarditis, but their use is generally not recommended because administration in experimental animal models has had deleterious effects.
Intravenous administration of immune globulin may have a use in preventing severe disease in immunocompromised individuals or those with life-threatening disease.
NOTE: The above information is educational purpose. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition.
DISCLAIMER: This information should not substitute for seeking responsible, professional medical care.
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