An Overview of Enterovirus and Its Different Strains

Enteroviruses are common viruses. There are many different enterovirus strains that can cause a variety of conditions, from very common infections—like hand, foot, and mouth disease and common colds—to deadly and rare viruses such as polio and encephalitis. Each strain can also cause a spectrum of symptoms ranging from the mild to severe.

One enterovirus strain, enterovirus-D68, or EV-D68, received a lot of attention as it spread respiratory disease in the fall of 2014. Another strain, EV-71, which can cause neurologic complications like encephalitis, has been seen in outbreaks in China. Fortunately, vaccines for EV-71 have been (and are being) developed, though they are not available in the U.S.

mother and daughter washing hands

Ariel Skelley / undefined

Key Facts about Enterovirus D-68

In 2014, as kids went back to school, EV-D68 spread rapidly in the U.S. It was first noted in Missouri and then spread throughout the Midwest, into the South and Northeast, and to the rest of the country. It particularly affected those with asthma.

  • Most affected are children
  • Children with asthma at most risk
  • Wash hands with soap and water (hand sanitizers are OK if soap is not available)
  • The virus can linger on countertops, doorknobs, and toys
  • Most children who are sick do not have a fever
  • Some children have difficulty breathing and need to go to the hospital
  • There is no vaccine or specific treatment. Most get better quickly
  • Enteroviruses are common illnesses. D-68 is just a rare strain.
  • Some cases are associated with muscle weakness or paralysis
  • Some cases are serious, but rates of death are not higher than with many other respiratory illnesses.


Enteroviruses are common viruses. They are common even when we don't hear about outbreaks. They, however, can cause sudden outbreaks of disease. In the U.S, 10-15 million people are infected by different strains annually. There is no specific treatment. There is no vaccine in the U.S. for enteroviruses, aside from the polio vaccine, which is not effective for preventing illness from EV-D68.

Most enterovirus infections cause no symptoms—or at most only a fever or a cold—and are never identified.

There are severe syndromes associated with particular subtypes, like EV-D68.

Respiratory: Enterovirus D68

Symptoms can be like a common cold. EV-D68 may, however, develop into a severe infection requiring hospitalization. Symptoms usually include difficulty breathing and wheezing. Most do not have a fever. Fewer than 1 in 4 people develop a fever.

Asthmatic children are at higher risk. Those initially hospitalized have been young (6 weeks to 16 years) and asthmatic (68%).

Anyone with difficulty breathing should immediately seek medical attention. There is no specific treatment. Oxygen and hospital care may be needed.

In August 2014, enterovirus-D68 was identified in children in Kansas City, Missouri. By October, it had reached 45 states. Well over 1,000 children were reported ill; 15% of those hospitalized needed intensive care. Sometimes kids' arms and legs can become weak, even paralyzed, like in polio. This "acute flaccid paralysis" has been tentatively associated with enterovirus D-68.

The disease has been rare around the world, though severe disease has been noted. Despite the severity of the disease, few deaths have been conclusively linked to the virus. In fact, EV-D68 was found to cause more severe disease, but not more deaths than other respiratory viruses, such as rhinoviruses (also an enterovirus).

Other Strains

There are different enterovirus types, with different strains varying around the world. Polioviruses are enteroviruses. The remaining non-polio enteroviruses are divided into four categories: Coxsackievirus A, Coxsackievirus B, Echovirus, and numbered Enteroviruses. There are 62 non-polio enteroviruses known to cause disease.


Rhinoviruses cause the common cold. Many cases are mild or not even noticed. Some cases can be serious and cause severe respiratory illness. There is no specific treatment or vaccine. It is spread by droplets—such as breathing in these droplets or by touching things with hands contaminated by these droplets.


Encephalitis is inflammation of the brain that causes tiredness, comas, seizures, and loss of movement or coordination.

EV71 is a serious infection in Asia, causing large outbreaks there, but not in the U.S. In can rarely cause neurologic effects, such as brain-stem encephalitis that delay neurodevelopment. A particular genotype C4 especially is associated with these outbreaks.

Two vaccines have been developed for this strain and appear promising - but only for EV71.

Hand Foot and Mouth Disease (HFMD)

Blisters develop on the hands, sometimes feet, and mouth that are clear or gray and surrounded by red rings. These hurt and last about 1 week.

Coxsackievirus A16 is the most common HFMD strain in the U.S, except Coxsackievirus A6 predominated in 2011-12. Coxsackievirus A6 causes more severe illnesses, sometimes needing hospitalization.


A few small "Mouth blisters" develop in the back of the mouth, near the tonsils, with a sore throat and fever. They may ulcerate. Blisters heal in 7-10 days.

Coxsackie A4, 10, 5, 6, 2 and 3 are associated.


Myopericarditis is the inflammation of the pericardium (sac surrounding the heart) and heart muscle. This can cause shortness of breath, fatigue, chest pain - often worse lying down. Patients can develop heart failure. This means they may have excess fluid in feet and lungs. In rare cases, heart damage may be life-threatening.

It can be caused by coxsackieviruses A4, B3, B2.

Acute Hemorrhagic Conjunctivitis (AHC)

Eyes appear bloodshot for 5-7-days, before resolving, usually without eye problems.

Coxsackievirus A24 and enterovirus 70 are associated with conjunctivitis and AHC.

Viral (Aseptic) Meningitis

Meningitis is the inflammation of the meninges (membrane surrounding the brain and spinal cord). Patients have fever, headache, and sometimes confusion. They may lose consciousness and have impaired function. 

Echoviruses 13, 18, and 30 are associated.


Enterovirus 70 rarely causes a polio-like paralysis.

Neonatal Sepsis

Severe neonatal sepsis occurs with coxsackievirus B1.


Fever with sudden chest pain in lower ribs from muscle damage.

It is rare and associated with Echovirus 1.

Long-Term Consequences

Enteroviruses are associated with autoimmune disorders. Some hypothesize type 1 diabetes and other disorders may develop after enterovirus infections.


Non-polio enteroviruses can be found in stool, eye, nose, or mouth secretions. The disease can spread by contact (handshakes), touching objects touched by others ("fomites"), changing diapers, drinking contaminated water. Patients can spread some strains through stool or respiratory secretions weeks after symptoms pass. Labor or breastfeeding can transmit infection. Symptoms usually develop 3-6 days after exposure.

Children's lack of prior exposure and immunity. There is only some cross-immunity between different enteroviruses; adults usually have had multiple strains.


Infections may cause no symptoms. To help prevent infection and transmission, wash your hands—especially before eating, when using a bathroom, changing diapers, or visiting anyone who is ill.

Wash your hands with soap and water, if available. If not, use an alcohol-based hand sanitizer and wash your hands as soon as possible. Avoid shaking hands. Cover sneezes with a tissue or upper sleeve. Clean surfaces. Avoid touching your face.

There is no vaccine in the U.S. Diagnosis is made by PCR or blood testing. There is no specific treatment.

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