Also called: Non Polio Enterovirus Infection, Enterovirus
Timothy Yarboro, M.D.
Enteroviruses are viruses that cause some of the most common viral infections. They enter the body through the respiratory or gastrointestinal tract and can easily multiply.
In most cases, people who become infected with an enterovirus do not become ill. Those who do become sick often have relatively mild symptoms similar to those associated with a common cold or the flu. However, some patients, especially infants, may experience more severe illnesses. Between 10 million and 15 million cases of symptomatic enterovirus infections are reported in the United States each year, according to the U.S. Centers for Disease Control and Prevention.
There are two major types of enteroviruses:
- Polioviruses. These viruses can cause poliomyelitis, a condition in which infected nerves cause temporary or permanent paralysis and even death. Polioviruses have been eliminated from the Western Hemisphere.
- Nonpolio enteroviruses. There are more than 60 nonpolio enteroviruses. They include coxsackie viruses and echoviruses.
People usually become infected with enteroviruses by coming into contact with the respiratory secretions of someone who is infected. Such secretions include saliva, sputum or nasal mucus. The stool of an infected person also can transmit the virus.
In the United States, enterovirus infections are most likely to occur in the summer and autumn. Enteroviruses affect people across all age groups and populations. However, children from infancy to adolescence are at higher risk of infection because they are less likely to have built up antibodies to these viruses.
The nature of the virus itself can be determined through various types of tests, including throat, stool or rectal cultures or from spinal fluid. In most cases, there is no standard treatment for an enterovirus infection. Instead, patients are urged to get plenty of rest and to drink fluids regularly while waiting for the virus to pass from the body. While vaccines have been effective in largely eliminating poliovirus infections, there is no vaccine available to treat nonpolio enteroviruses. The best method of preventing these infections is to follow the steps associated with reducing the risk of most viral infections.
About enterovirus infection
Enteroviruses cause some of the most common viral infections. Only common cold viruses cause more viral infections than enteroviruses. Each year, between 10 million and 15 million cases of symptomatic enterovirus infections are reported in the United States, according to the U.S. Centers for Disease Control and Prevention (CDC). Enteroviruses are highly contagious.
These viruses derive their name from the fact that they usually begin their infection in the gastrointestinal tract, although they may not cause specific disease there. They are more likely to affect the central nervous system or upper respiratory tract.
Enteroviruses are made up of ribonucleic acid (RNA) and protein. Viruses are classified as either RNA viruses or deoxyribonucleic acid (DNA) viruses. An RNA virus must first turn its RNA into DNA and then insert itself into the host’s DNA. The viral genes are then copied many times, using the process the host cell would normally use to reproduce its own DNA.
In most cases, people who become infected with an enterovirus do not become ill. Those who do become sick often have relatively mild symptoms similar to those associated with a common cold or the flu. However, some patients may experience more severe illnesses. Some people infected with an enterovirus may go on to develop viral meningitis. In rare cases, an enterovirus infection can lead to illnesses that affect the heart (myocarditis) or brain (encephalitis). Other enterovirus infections may lead to paralysis. In newborns, enterovirus infections can replicate rapidly in certain organs and quickly become fatal.
However, in most cases, patients who become ill after an enterovirus infection do not experience long-term complications, especially if the illness is mild or if it involves viral meningitis. However, some patients who experience polio virus-related paralysis or encephalitis may have permanent health problems. Patients with myocarditis also may develop heart failure that requires long-term care. Scientists also believe that enterovirus infections may play a role in the development of juvenile-onset diabetes mellitus. Enterovirus infections do not appear to follow any discernible patterns. Outbreaks are sometimes national or regional and tend to vary from year to year. No long-term trends have been discovered, according to the CDC.
Types and differences of enterovirus infection
There are two major types of enteroviruses: polioviruses and nonpolio enteroviruses.
There are three polioviruses that each cause poliomyelitis, a condition in which infected nerves cause temporary or permanent paralysis and even death. These viruses have been eliminated from the Western Hemisphere, the Western Pacific and European regions as a result of widespread use of polio vaccines. However, polioviruses remain problematic in certain other areas of the word (e.g., India).
On the other hand, there are more than 60 nonpolio enteroviruses. They can cause fever and other illnesses. Nonpolio enteroviruses include:
- Coxsackie viruses. Named after Coxsackie, New York, where these viruses were first discovered. These nonpolio enteroviruses include 23 coxsackie A viruses and 6 coxsackie B viruses.
- Echoviruses. There are 28 of these enteric cytopathic human orphan (echo) viruses.
- Several other nonpolio enteroviruses remain unclassified.
Risk factors and causes of enterovirus infection
People usually become infected with enteroviruses by coming into contact with the respiratory secretions of someone who is infected. Such secretions include saliva, sputum or nasal mucus. The stool of an infected person also can transmit the virus and can be transmitted to others through poor hygiene.
Germs associated with enteroviruses are often transferred to surfaces or objects, such as door handles or telephones. People become contaminated by touching these objects, and then infect themselves by touching their eyes, mouth or nose with contaminated fingers. Parents and other caregivers who change an infected infant’s diaper may also become contaminated through contact with the infant’s stool.
Consuming contaminated foods or liquids can also result in enterovirus infection. Sewage contamination of water supplies can cause enterovirus epidemics. It does not appear that enteroviruses can be spread through blood transfusions or insect bites.
In the United States, enteroviruses are most likely to occur in the summer and autumn. Enteroviruses affect people across all age groups and populations. However, children from infancy to adolescence are at higher risk of infection because they are less likely to have built up antibodies to these viruses. They are also less likely to practice good hygiene, such as hand washing. People who live in high-density populations and are not able to practice good hygiene are also at an increased risk of infection. Enterovirus infections during pregnancy do not appear to cause significant harm to the fetus, although data on this subject remains limited. Mothers who are infected shortly before delivery sometimes pass an enterovirus infection onto their child. In such situations, illness typically is mild. However, some newborns develop infections that can harm many organs, including the liver and heart. This can be fatal and is most likely to occur during the first two weeks of life.
Signs and symptoms of enterovirus infection
Enterovirus infections are very common. Most people do not experience illness after becoming infected. However, those who do become ill typically develop symptoms between three and six days after infection. In many cases, these symptoms resemble those of a mild cold or a stronger flu-like illness.
Fever is the most common symptom of infection with nonpolio enteroviruses. Other symptoms may include:
- Achy muscles
- Loss of appetite
- Nausea and vomiting
- Sore throat
Symptoms typically last for three or four days, with most cases resolving within one week.
Several illnesses are associated with nonpolio enterovirus infections. They include:
- Herpangina. Infection of the throat that causes red-ringed blisters and ulcers of the tonsils and soft palate. It is typically associated with coxsackie A enteroviruses.
- Hand, foot and mouth disease. Common viral illness of children that causes painful red blisters on the throat or tongue, gums, the inside cheeks, palms of the hand and soles of the feet. It is typically associated with coxsackie A enteroviruses.
- Pleurodynia. Infection that causes painful spasms of the muscles in the chest and upper abdomen. It is typically associated with coxsackie B enteroviruses.
- Heart inflammation. Inflammation of the heart muscle (myocarditis) and the fluid-filled sac surrounding the heart (pericarditis). These conditions can cause fever, chest pain, shortness of breath and fatigue. It is estimated that enteroviruses cause up to one-third of all cases of myocarditis. It is typically associated with coxsackie B enteroviruses.
- Viral meningitis. Inflammation of the meninges, the membranes covering the brain and spinal cord, which may cause fever and chills, severe headache, changed mental status and other symptoms. The vast majority of cases of viral meningitis in children and young adults in which a cause can be identified are attributed to enteroviruses.
- Acute gastroenteritis. Inflammation of the stomach and intestines that cause diarrhea and vomiting. Often called the “stomach flu.”
- Viral pharyngitis. Inflammation of the pharynx, the part of the throat between the tonsils and the larynx (voice box). It causes a sore throat.
- Pneumonia. Inflammation of the lungs that causes fever, sharp or stabbing chest pains, cough, green or yellow mucus and other symptoms.
- Hemorrhagic conjunctivitis. Infection of the whites of the eyes.
- Encephalitis. Inflammation of the brain that cause many symptoms, including fever, vomiting, confusion and unsteady gait.
Diagnosis and treatment of enterovirus
In diagnosing an enterovirus infection, a physician performs a complete physical examination and compiles a thorough medical history. Seasonal outbreaks of infections may also provide the physician with the likely diagnosis. The nature of the virus itself can be determined through various types of tests, including cultures from the throat, stool or rectum or from spinal fluid. More involved diagnostic procedures may be used, including imaging tests such as echocardiograms of the heart, electrocardiograms (EKG) to diagnos pericarditis and myocarditis, and chest x-rays to diagnose pneumonia.
In most cases, there is no standard treatment for an enterovirus infection. Patients are urged to get plenty of rest and to drink fluids regularly while waiting for the virus to pass from the body. Fever reducer and pain reliever medications also may help relieve symptoms. However, patients should not take any medications, including over-the-counter varieties, without first consulting a physician. Children and teens should not take medications that contain aspirin for symptoms related to a viral illness. Aspirin used after a viral infection can cause Reye syndrome, a rare but sometimes fatal condition.
Patients with less severe illnesses usually recover completely. However, infections of organs such as the liver or the heart may be fatal.
Prevention methods for enterovirus infection
While vaccines have been effective in largely eliminating poliovirus enterovirus infections, there is no vaccine available to treat nonpolio enteroviruses. The best method of preventing these infections is to follow the steps associated with reducing the risk of most viral infections.
People are urged to regularly wash their hands to help prevent the spread of germs. Patients should cough or sneeze into tissues rather than into their hands or over surfaces. Contaminated surfaces should be cleaned with soap and water and a disinfectant.
Questions for your doctor about enterovirus
Preparing questions in advance can help patients have more meaningful discussions with healthcare professionals regarding their conditions. Patients may wish to ask their doctor the following questions related to enterovirus infection:
- How will I know if I have an enterovirus infection, particularly if I have no symptoms?
- How will you diagnose my enterovirus infection?
- Does my infection pose any serious health risks?
- What are my treatment options?
- Can I take fever reducers and pain relievers to help reduce symptoms?
- What are some tips for reducing my risk of enterovirus infection?
- How can I keep my family from contracting my infection?
- How can I reduce the risk of consuming food or water contaminated with an enterovirus?
- How can I find out if I received my polio vaccination as a child?
- How can I reduce my child’s risk of an enterovirus infection?