Enteroviruses are small, icosahedral, single-stranded, positive-sense RNA viruses. Numbered enteroviruses cause a range of illnesses from mild (‘hand, foot and mouth disease’) to severe neurological and respiratory problems in immunosuppressed people.
They are usually transmitted by the fecal-oral route. There are no vaccines against non-polio enteroviruses. They usually come into widespread circulation in late summer and autumn (in temperate climates). They are grouped alphabetically by their genome and serotyped according to neutralization assays.
Symptoms
The symptoms of enteroviruses depend on the virus and which part of the body is affected. In most cases, the illness is mild and similar to a cold or flu. However, some types of enteroviruses can cause serious problems.
The Coxsackie A virus causes herpangina, which most often affects infants and children. The disease is characterized by the sudden appearance of fever, a sore throat, loss of appetite, and mouth or throat ulcers that appear as grayish bumps. The condition usually lasts 4 to 6 days. Infection with herpangina does not usually lead to complications, but in a small number of patients it can cause aseptic meningitis, encephalitis, myocarditis, pericarditis, and pneumonia.
Echoviruses 13 and 18 can cause viral meningitis, which is inflammation of the membranes that surround the brain and spinal cord. It most commonly affects young children and people with weakened immune systems. This type of enterovirus is also known to cause acute flaccid myelitis, a severe weakness of the arms and legs, in people with weakened immune systems.
Some enteroviruses can cause rashes. The rash associated with herpangina, coxsackie A virus, and human parechovirus is nonpruritic and does not desquamate; it occurs on the hands, face, neck, and chest and may be maculopapular, petechial or vesicular. A rash may also be present in herpangina, aseptic meningitis, and some other infections.
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Most of the other enteroviruses do not cause a rash. However, some can cause a rash, especially during epidemics, including Coxsackie A virus and human parechovirus. Infection with herpangina, coxsackie virus A4, and human parechovirus can lead to a neurological disorder called limb weakness and stiffness syndrome (LSS). In LSS, the muscles of the legs and arms become weak or stiff. The symptoms usually occur in a few weeks after infection and go away in a few months.
Many enteroviruses spread easily from person to person. The viruses can be spread on unwashed hands, contaminated surfaces, and through droplets when someone coughs or sneezes. They can also be spread through fluid in skin blisters. Until the infection goes away, the virus can live for several days on contaminated surfaces and in the stool of an infected person.
Prevention
There are more than 100 different enteroviruses, and most cause cold-like symptoms such as a sore throat and fever. Some types, such as the one causing this outbreak, also have a rash and are called hand, foot and mouth disease (also known as coxsackievirus). A few enteroviruses, such as EV-D68, can lead to severe respiratory symptoms that can make people with asthma feel worse.
Symptoms of an enterovirus infection usually clear up within a week. Over-the-counter medicines can help relieve them. There is no vaccine to prevent non-polio enteroviruses, but good hygiene can limit their spread. Wash hands often, especially after using the toilet and changing diapers, before eating, and after touching commonly touched surfaces in public places. Cover coughs and sneezes with a tissue or your upper sleeve, and avoid close contact with sick people. Clean and disinfect frequently-touched objects in your home, such as toys, and wash clothing and towels that come into contact with an infected person.
Children are most likely to develop serious illness from enterovirus infections, but they can affect adults as well. Infants are particularly susceptible to complications from enteroviruses because their immune systems are not fully developed. Young children may get a rash with blisters or sores inside their mouth and throat, but more rarely, an enterovirus can infect the central nervous system and cause paralytic poliomyelitis or aseptic viral meningitis.
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Non-polio enteroviruses cause 10 to 15 million infections and tens of thousands of hospitalizations in the United States each year. They include the viruses that cause poliomyelitis, hand, foot and mouth disease, aseptic viral meningitis and acute flaccid myelitis causing weakness and paralysis in children. A mix of enteroviruses circulate each year, and the type that is common in a given year varies.
There are no medications that can kill enteroviruses, so antibiotics do not treat the infections they cause. Instead, treatment focuses on helping patients to feel comfortable with pain relievers and by drinking plenty of fluids. The CDC has more information on the current outbreak of enteroviruses, including detailed information about the virus, its symptoms and how it is spreading.
Outbreaks
Infection with enteroviruses often causes symptoms such as fever, sore throat and headache, which resemble those of the common cold. In some cases, they may also cause vomiting and diarrhea. Some strains of the virus can also lead to a generalized, nonitchy rash and sores inside the mouth. Rarely, the virus can progress to attack and infect a particular organ such as the heart, brain, nervous system, intestines or lungs resulting in more serious illness.
The most common way for people to get enterovirus infections is through direct contact with the respiratory secretions and fecal material from an infected person. Infection can also happen if a person eats or drinks something that has been contaminated by these materials. Infected people are most contagious during the first week of being sick.
Enteroviruses are very common. In the United States, these viruses impact 30-50 million people each year – many of whom will be hospitalized and/or permanently injured or even killed as a result of these illnesses.
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These viruses are very easily passed from person to person by direct contact in crowded environments such as school classrooms, day care centers and shopping malls. They can also spread if an infected person has faecal material on their hands and then touches objects that other people may touch. Infants, children and adults with immature immune systems are at the highest risk of enterovirus infection.
People with certain types of weakened immune systems or chronic conditions like type 1 diabetes are also at increased risk for contracting enteroviruses. For example, infants who are born with CMV encephalitis (an immune-mediated brain disease) have been known to develop severe enteroviruses infections.
Outbreaks of enteroviruses occur periodically around the world. They usually affect children under 5 years of age and may coincide with hand, foot and mouth disease outbreaks. In 2014, a strain of enterovirus called EV-D68 became a widespread concern in the U.S. The virus was found in both children and adults with a range of symptoms – some mild and some severe. This was the first time that EV-D68 had been reported in the United States and it is not clear what caused this outbreak.
Diagnosis
Acute enterovirus infections can be difficult to distinguish from other illnesses that children may have. Children might have a fever, cough or stomach pain. They might also have rashes or spots in their mouths, hands or feet. Some of these viruses can cause serious illness in infants and young children. These include polio, aseptic meningitis, central nervous system infection and heart failure.
Most enteroviruses are spread through direct contact with an infected person’s saliva, mucus or faeces (poo). Some types of enteroviruses also can be transferred from person to person when they touch food or fluids contaminated by the virus. Children often catch these viruses from other children in the same age group or class.
There are over 100 different human enteroviruses. Most of these are not dangerous and most people who get infected do not develop any symptoms at all. In some cases, such as in the case of hand, foot and mouth disease, the illness only lasts a week or so before it clears up with no lasting problems. There are a small number of enteroviruses, however, that can cause more severe illness in those with weakened immune systems. These can include the polioviruses, which cause poliomyelitis, or the EV-D68 and EV-A71 viruses, which are associated with a number of clinical syndromes including encephalitis, aseptic meningitis and acute flaccid paralysis.
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Diagnosing an enterovirus infection requires a physical examination and sometimes blood tests or samples of material from the throat, stool or cerebrospinal fluid. These are sent to a laboratory for analysis. There is no treatment to cure the infection but medical care can help relieve symptoms such as fever and pain. Rarely, the enteroviruses can cause heart and central nervous system diseases that can be fatal.
Recent advances in the understanding of these viruses have resulted in a revision of species nomenclature, genus reorganization and expansion of serotypes from 64 to over 200. A new classification system based on the RNA coding region and serotype numbers has been developed to replace the old host names and disease designations. This has resulted in some confusion and overlap for many of the older and newer enteroviruses.
