Enteroviruses
Enteroviruses are a group of viruses that can infect multiple organ systems, including the central nervous system, skin, eyes, and heart. This class includes well-known viruses such as poliovirus, coxsackieviruses, and echoviruses. Transmission typically occurs through direct contact with fecal matter or contaminated food and water. Symptoms of enterovirus infections can vary widely and may include fever, muscle weakness, rash, headache, neck stiffness, confusion, and lethargy. While many infections are self-limiting and resolve on their own, severe cases may require supportive care, such as hydration and antipyretics, and in critical situations, life support measures may be necessary. Common clinical manifestations include viral meningitis, encephalitis, and conditions like hand-foot-mouth disease, particularly in children. Preventative measures, such as good hygiene practices, are crucial to reduce the spread of enteroviruses. Vaccination efforts, especially against poliovirus, have significantly reduced the incidence of polio in many parts of the world, contributing to public health initiatives aimed at global eradication.
Enteroviruses
ANATOMY OR SYSTEM AFFECTED: Brain, eyes, heart, nervous system, skin
DEFINITION: A class of viruses capable of infecting multiple organ systems, such as the central nervous system, the skin, the eyes, and the heart.
CAUSES: Virus
SYMPTOMS: Fever, muscle weakness, rash, headache, neck stiffness, confusion, lethargy
DURATION: Acute or chronic
TREATMENTS: Supportive care, hydration, antipyretics; critical life support measures in severe cases; intravenous immunoglobulins
Causes and Symptoms
Enteroviruses are a class of viruses that include the well-known poliovirus and also coxsackieviruses, echoviruses, and other enteroviruses. Genetically, they are small, nonenveloped, single-stranded viruses that belong to the family Picornaviridae. These viruses are ubiquitous and infections occur year-round.
Enteroviruses cause a variety of clinical syndromes with different clinical manifestations depending on the specific viruses involved. Typically, is through direct contact with fecal matter and contaminated food or water. The virus usually replicates initially in the throat and the small intestine, from where it then spreads to other organs.
Rash is a symptom common in all enterovirus infections. A maculopapular rash (mixture of flat and raised spots) can be seen in echovirus and poliovirus infections. Coxsackieviruses can cause the hand-foot-mouth syndrome in children, which presents as fever and vesicles in the oral cavity, hands, feet, buttocks, and sometimes genitalia. Transmission is through direct contact, and the illness usually resolves in two to three days. Herpangina is another syndrome caused by coxsackieviruses; it presents with painful vesicular lesions on the and soft palates in children. Echovirus and coxsackievirus can both cause a petechial (small, red or purple spots), which sometimes may be confused with a meningococcal infection.
The (CNS) is a well-known site of enteroviral infections. Enteroviruses as a group is the most common cause of viral meningitis in adults, which is usually due to echoviruses and coxsackieviruses. Because infants are not able to verbalize, they usually exhibit signs of irritability and fever, whereas in adults the common complaints are fever, headache, stiff neck, nausea, and vomiting. Encephalitis, the swelling and of the brain, is usually also the result of coxsackieviruses and echoviruses. It can develop either as a of or as an isolated event. Encephalitis typically presents as fever, lethargy, headache, seizures, or confusion. Paralytic is the well-known syndrome due to polioviruses, but this presentation is the least common, since most people who have been infected with poliovirus do not have symptoms and only a minority of patients develop meningitis. Those who do develop usually present with a progressive, asymmetric weakness. The legs are commonly involved, followed by the arms and abdominal, chest, or throat muscles. It is the involvement of respiratory and throat muscles that may be life threatening since these patients are prone to respiratory failure. While muscle paralysis is the hallmark of poliovirus infection, a similar picture may also be seen with echovirus infections, although the symptoms are not as severe or persistent.
Enterovirus and coxsackievirus are also capable of causing eye infections, commonly known as acute hemorrhagic conjunctivitis (AHC), with red eyes, pain, and swelling of the eyelids.
Coxsackieviruses can affect the chest and abdominal muscles, causing what is known as pleurodynia, which presents as fever and spasms of the chest and abdominal muscles. Coxsackievirus infection of the heart muscles and its surrounding tissues, known as myopericarditis, can present with mild symptoms such as chest pain or severe and rapid progression to and death.
Treatment and Therapy
Because most enteroviral infections are self-limited and resolve spontaneously, specific treatments are not warranted. In cases of severe infections—such as paralytic disease, meningitis, or myocarditis—supportive therapies are needed as life preservation measures. Even in such severe cases, no specific antiviral agents are available. Serum intravenous has been tested in patients with certain immunodeficiencies and in neonates, although results have been mixed.
As in most infections, prevention is just as important as treatment. Because enteroviral infections are transmitted through contaminated sources, it is imperative to exercise good judgment regarding handwashing and hygienic practices.
Perspective and Prospects
As one of the most recognized members of the enteroviral class, poliovirus has come a long way since its isolation in 1909 by Karl Landsteiner and Erwin Popper. The development of polio vaccines along with implementation of polio eradication programs have largely eliminated the disease due to wild-type poliovirus. The virus has been largely eradicated in the United States and other developed countries, and it is targeted for imminent global eradication.
The first polio was developed in 1952 by Jonas Salk. It was developed as an injectable vaccine using dead virus and is known as the inactivated polio vaccine (IPV). Doses are given at two, four, and six to eighteen months and at four to six years of age. Albert Sabin subsequently developed an oral polio vaccine (OPV) in 1962 that utilizes an attenuated but live poliovirus. Dosing is the same as that for the inactivated polio vaccine. A major concern of the oral polio vaccine is its ability to cause vaccine-induced polio, although the likelihood is very low, with rates of approximately 1 in 2.5 million vaccine recipients. Since most wild-type poliovirus have been eradicated, most cases of poliomyelitis in the twenty-first century are attributed to vaccine-induced poliomyelitis.
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