Enteroviruses: Polio and Non-Polio Types, Symptoms, Risks

Author: Ian C. Langtree - View Credentials
Published: 26 Feb 2014 - Updated: 12 Nov 2026
Publication Type: Informative

Table of Contents:
Synopsis - Definition - Overview - FAQs - Insights, Updates - Related Content

Synopsis

This information gives a plain-language overview of the enterovirus family, from the coxsackieviruses and echoviruses to EV-A71, EV-D68 and the three polioviruses, and is drawn from surveillance data and guidance published by the Centers for Disease Control and Prevention, the World Health Organization, the Global Polio Eradication Initiative and reports in MMWR Morbidity and Mortality Weekly Report and PLoS ONE. Non-polio enteroviruses cause an estimated 10 to 15 million infections in the United States every year, mostly mild and mostly in infants, children and teenagers, yet a small share lead to meningitis, heart inflammation or paralysis. It also sets out where polio stands today: wild poliovirus cases are down by more than 99 percent since 1988 and the virus remains endemic only in Afghanistan and Pakistan. The material is useful for parents, caregivers, people with weakened immune systems, and seniors and people with disabilities who are living with the long-term effects of polio or caring for someone who is.

At a Glance

• 1 - The CDC has confirmed 801 cases of acute flaccid myelitis in the United States since August 2014, with peaks in 2014, 2016 and 2018.
• 2 - Post-polio syndrome affects between 25 and 40 of every 100 polio survivors. It begins about 15 to 40 years after the original infection.
• 3 - China recorded 488,955 cases of hand, foot, and mouth disease and 126 deaths in 2008. Enterovirus A71 accounted for 95.3 percent of the fatal cases.
• 4 - There is no vaccine and no specific antiviral treatment for non-polio enteroviruses, so care is supportive and most people recover completely.

Topic Definition

Enteroviruses

Enteroviruses are a genus of small, non-enveloped, single-stranded RNA viruses in the family Picornaviridae that spread from person to person, mainly through contact with respiratory secretions or stool from an infected person. The genus includes the three polioviruses, which cause poliomyelitis, and the non-polio enteroviruses - the coxsackieviruses, echoviruses and numbered types such as EV-A71 and EV-D68. Most infections cause no symptoms or a mild illness with fever, cold-like symptoms or a rash, but some lead to hand, foot, and mouth disease, viral meningitis, myocarditis, encephalitis or paralysis. Polio can be prevented by vaccination, while there is no vaccine and no specific antiviral treatment for the non-polio enteroviruses, so care is supportive.

Overview

Enteroviruses are a large genus of small RNA viruses in the family Picornaviridae. They are among the most common viruses that infect people, they spread easily, and they are usually talked about in two groups: the three polioviruses, and the non-polio enteroviruses, which take in the coxsackieviruses, the echoviruses and the newer numbered types such as EV-A71 and EV-D68. Virologists now sort the genus by genetics rather than by the illness each virus causes. It is divided into species Enterovirus A through L plus three rhinovirus species, and more than 300 virus types have been characterized genetically across the genus [International Committee on Taxonomy of Viruses, n.d.].

Most enterovirus infections pass with no symptoms or with a mild, cold-like illness. A small share lead to serious disease, including meningitis, inflammation of the heart and paralysis. Wild poliovirus has been eliminated in the United States, but polio has not been eradicated worldwide, and the symptoms of any enterovirus infection can differ a great deal from one person to the next.

Non-Polio Enteroviruses

Non-polio enteroviruses cause about 10 to 15 million infections and tens of thousands of hospitalizations in the United States each year [Centers for Disease Control and Prevention, 2024a]. Infants, children and teenagers are the most likely to become ill because they have not yet built up immunity, which makes these viruses a regular part of pediatric health care. Infants and people with weakened immune systems have a greater chance of complications. The viruses pass from person to person through close contact, through contaminated objects and surfaces, and during diaper changes.

The traditional groups of non-polio enteroviruses are:

• Coxsackie A viruses
• Coxsackie B viruses
• Echoviruses
• Numbered enteroviruses

Mild illness usually means fever, a runny nose, sneezing, cough, a skin rash, mouth blisters, and body and muscle aches. Recognized complications include viral conjunctivitis, hand, foot, and mouth disease, viral meningitis, viral encephalitis, myocarditis, pericarditis, acute flaccid paralysis and inflammatory muscle disease. Newborns can, very rarely, develop sepsis, and non-polio enteroviruses may play a role in the development of type 1 diabetes in children [Centers for Disease Control and Prevention, 2024e].

There is no vaccine against non-polio enterovirus infection and no specific antiviral treatment. Care is supportive - rest, fluids and relief of pain and fever - and most people recover completely [Centers for Disease Control and Prevention, 2024a]. Prevention rests on handwashing, cleaning and disinfecting surfaces, and avoiding close contact with people who are sick.

The Coxsackieviruses

As with other enteroviruses, the most common result of a coxsackievirus infection is a mild feverish illness, even during an outbreak. The coxsackieviruses were originally classified into two groups, A and B, based on the disease they produced in newborn mice. Under the current genetic system the old groups are spread across several species: coxsackie A types are found in Enterovirus A, B and C, while the coxsackie B viruses belong to Enterovirus B [International Committee on Taxonomy of Viruses, n.d.].

Coxsackie A Viruses

Group A coxsackieviruses are best known for hand, foot, and mouth disease (HFMD), herpangina (painful blisters at the back of the throat) and acute hemorrhagic conjunctivitis. Coxsackievirus A16 is typically the most common cause of HFMD in the United States, and coxsackievirus A6 can also cause it, sometimes with more severe symptoms [Centers for Disease Control and Prevention, 2024d].

Coxsackie B Viruses

Group B coxsackieviruses are associated with pleurodynia (sudden, severe chest and upper abdominal muscle pain), aseptic meningitis, meningoencephalitis, pericarditis and myocarditis. Treatment of pleurodynia consists mainly of pain relief. Myocarditis is the complication of most concern, because some people go on to have heart failure and need long-term care [Centers for Disease Control and Prevention, 2024e].

The Echoviruses

"Echo" began as an acronym for "enteric cytopathic human orphan" virus. An orphan virus is one that is not associated with any known disease, which is how these viruses looked when they were first isolated. Echoviruses have since been linked to a range of illnesses, most often fever with a rash and aseptic (viral) meningitis, but the original name is still in use. Genetically, echoviruses such as types 7 and 11 sit within the species Enterovirus B [International Committee on Taxonomy of Viruses, n.d.].

Enteroviruses identified more recently are not placed in the coxsackie or echo groups at all. They are simply numbered, with a letter showing the species, as in EV-A71 and EV-D68. There are far more of these than the handful known a few decades ago: Enterovirus A currently holds 25 types, Enterovirus B 63, Enterovirus C 23 and Enterovirus D 5 [International Committee on Taxonomy of Viruses, n.d.].

Enterovirus 71 Infections

Enterovirus A71 (EV-A71, formerly enterovirus 71) may cause no symptoms, or it may cause rash, fever and hand, foot, and mouth disease. It is notable for its role in epidemics of severe neurological disease in young children. It has been associated with cases and outbreaks in East and Southeast Asia and, although this is rare, with more severe disease such as encephalitis [Centers for Disease Control and Prevention, 2024d].

During an outbreak in Taiwan from April to July 1998 there were approximately 90,000 reports of HFMD among young children. About 320 children were hospitalized and at least 55 died [Centers for Disease Control and Prevention, 1998]. In mainland China, the World Health Organization reported 1,884 cases and 20 deaths in Fuyang city, Anhui Province, by April 29, 2008 [World Health Organization, 2008]. By the end of that year the national surveillance system had recorded 488,955 HFMD cases, of which 1,165 were severe and 126 were fatal, and EV-A71 accounted for 95.3 percent of the fatal cases. In 2009 the totals rose to 1,166,131 cases and 353 deaths [Tan et al., 2011].

Enterovirus D68 and Acute Flaccid Myelitis

Enterovirus D68 (EV-D68) behaves more like a cold virus than a gut virus. It typically causes respiratory illness that can be mild or can progress to wheezing, difficulty breathing or pneumonia. EV-D68 can also cause acute flaccid myelitis (AFM), an uncommon but dangerous neurological condition that mostly affects children, with weakness that can start several weeks after the infection [Centers for Disease Control and Prevention, 2025].

AFM looks very much like polio: a sudden onset of weakness in one or more arms or legs. The CDC has confirmed 801 cases since it began tracking AFM in August 2014, in 49 states and the District of Columbia. Cases rose sharply in 2014 (120 cases from August to December), 2016 (153) and 2018 (238), most patients became ill between August and November, and enteroviruses are considered the likely cause of the peak years. Numbers have been much lower since then, with 17 confirmed cases in 2025 [Centers for Disease Control and Prevention, 2026]. Some people with AFM are left with lasting weakness, which places it among the neurological disorders that can lead to long-term disability.

The Polioviruses

The polioviruses are the three enterovirus serotypes (types 1, 2 and 3) that cause poliomyelitis, also called polio or, in older writing, infantile paralysis. Poliovirus spreads from person to person by the fecal-oral or oral-oral routes. The disease it causes ranges from an infection that is never noticed to paralysis, and most infections fall at the mild end of that range [Centers for Disease Control and Prevention, 2024c]:

• Asymptomatic infection: about 70 percent of infections in children cause no symptoms at all.
• Abortive polio: about 24 percent cause a minor illness with fever, sore throat, headache, loss of appetite, abdominal pain or vomiting, and no neurological symptoms.
• Non-paralytic polio: 1 to 5 percent cause aseptic meningitis, with stiffness of the neck, back or legs, usually after a few days of minor illness.
• Paralytic polio: fewer than 1 percent of infections cause flaccid paralysis.

Paralytic polio is classified by the part of the nervous system involved. Among U.S. cases from 1969 to 1979, 79 percent were spinal polio, with weakness of the limbs that is often uneven from one side to the other; 2 percent were bulbar polio, which affects the cranial nerves that control swallowing, speech and breathing; and 19 percent were bulbospinal, a combination of the two. Death occurs in 2 to 5 percent of paralytic cases in children, 15 to 30 percent in adolescents and adults, and 25 to 75 percent when there is bulbar involvement [Centers for Disease Control and Prevention, 2024c].

The United States recorded more than 21,000 paralytic cases in 1952. The last case caused by wild poliovirus acquired in the country was in 1979, but the risk has not gone entirely. In June 2022 an unvaccinated young adult in Rockland County, New York, was paralyzed by a vaccine-derived poliovirus type 2, and related virus was found in local wastewater [Link-Gelles et al., 2022].

There is no cure for polio, but it can be prevented. The United States has used only inactivated polio vaccine (IPV) since 2000, and children receive four doses: at 2 months, 4 months, 6 through 18 months, and 4 through 6 years of age [Centers for Disease Control and Prevention, 2024f].

Post-Polio Syndrome

For many survivors polio did not end with recovery. Post-polio syndrome begins about 15 to 40 years after the original infection and affects between 25 and 40 of every 100 polio survivors. It is rarely life-threatening [Centers for Disease Control and Prevention, 2024b]. The usual features are new muscle weakness, fatigue and muscle atrophy [National Institute of Neurological Disorders and Stroke, 2026]. Older adults who had polio as children, and their caregivers, should raise any new weakness or loss of stamina with a physician, since mobility aids, bracing and energy management can often be adjusted to match.

The Global Polio Eradication Initiative

Since the Global Polio Eradication Initiative began in 1988, cases caused by wild poliovirus have fallen by more than 99 percent, from an estimated 350,000 cases in more than 125 endemic countries to endemic transmission in just two, Afghanistan and Pakistan. The WHO Region of the Americas was certified polio-free in 1994, followed by the Western Pacific Region in 2000, the European Region in June 2002, the South-East Asia Region, including India, on March 27, 2014, and the African Region in 2020. One in 200 infections leads to irreversible paralysis, which is why even small numbers of cases matter [World Health Organization, 2025].

Two of the three wild strains are gone. Eradication of wild poliovirus type 2 was certified in 2015, and type 3, last detected in northern Nigeria in 2012, was declared eradicated on October 24, 2019 [World Health Organization, 2019]. Only wild type 1 remains. For 2025 the initiative lists 31 wild type 1 cases in Pakistan and 21 in Afghanistan, and for 2026 it lists 50 in Afghanistan and 8 in Pakistan as of early October [Global Polio Eradication Initiative, 2026].

The other challenge is circulating vaccine-derived poliovirus. In communities where too few children are immunized, the weakened virus in oral polio vaccine can keep spreading and, over time, regain the ability to paralyze. The Democratic Republic of the Congo alone has reported 93 cases of circulating vaccine-derived poliovirus type 2 so far in 2026 [Global Polio Eradication Initiative, 2026]. Until every form of poliovirus stops circulating, high vaccination coverage remains the only reliable protection in every country.

More on this topic: Pediatric Health publications.

Frequently Asked Questions

How long is a person with an enterovirus contagious?

A person can spread a non-polio enterovirus for weeks, according to the CDC, including after they feel better. Careful handwashing, especially after using the toilet or changing diapers, remains important throughout that time.

What time of year are enterovirus infections most common?

In the United States, non-polio enterovirus infections are most common during summer and fall, although a mix of enteroviruses circulates every year.

Can adults get enterovirus infections?

Yes. Anyone can be infected, but infants, children and teenagers are more likely to become ill because they do not yet have immunity from earlier exposure. Adults with weakened immune systems have a greater chance of complications.

How long after infection does polio paralysis appear?

When paralysis occurs, it usually begins 7 to 21 days after infection with poliovirus. Nonparalytic illness has a shorter incubation period of about 3 to 6 days.

Do adults in the United States need a polio vaccine?

Since 2023 the Advisory Committee on Immunization Practices has recommended that adults who are known or suspected to be unvaccinated or incompletely vaccinated complete a primary series with inactivated polio vaccine. Fully vaccinated adults at increased risk of exposure may receive a single lifetime booster dose, and a health care provider can advise on individual circumstances.

How effective is the inactivated polio vaccine?

According to the CDC, two doses of inactivated polio vaccine provide at least 90 percent protection against paralytic polio and three doses provide at least 99 percent protection.

Is post-polio syndrome contagious?

No. Post-polio syndrome is not contagious, and only someone who has previously had polio can develop it. Not everyone who has had polio will go on to develop the syndrome.

Are children with asthma at higher risk from enterovirus D68?

Children with asthma may be at higher risk for severe symptoms from EV-D68, such as wheezing and difficulty breathing. Families can ask their health care provider about keeping an up to date asthma action plan.

References

• Centers for Disease Control and Prevention. (1998). Deaths among children during an outbreak of hand, foot, and mouth disease - Taiwan, Republic of China, April - July 1998. MMWR Morbidity and Mortality Weekly Report, 47(30), 629 - 632.
• Centers for Disease Control and Prevention. (2024a). About non-polio enteroviruses.
• Centers for Disease Control and Prevention. (2024b). About polio in the United States.
• Centers for Disease Control and Prevention. (2024c). Chapter 18: Poliomyelitis. In Epidemiology and prevention of vaccine-preventable diseases.
• Centers for Disease Control and Prevention. (2024d). Hand, foot, and mouth disease: Causes and how it spreads.
• Centers for Disease Control and Prevention. (2024e). Non-polio enteroviruses symptoms and complications.
• Centers for Disease Control and Prevention. (2024f). Polio vaccination.
• Centers for Disease Control and Prevention. (2025). About enterovirus D68.
• Centers for Disease Control and Prevention. (2026). AFM cases and outbreaks.
• Global Polio Eradication Initiative. (2026). Polio this week. Country updates as of October 4, 2026.
• International Committee on Taxonomy of Viruses. (n.d.). Genus: Enterovirus. In ICTV report: Picornaviridae.
• Link-Gelles, R., Lutterloh, E., Schnabel Ruppert, P., et al. (2022). Public health response to a case of paralytic poliomyelitis in an unvaccinated person and detection of poliovirus in wastewater - New York, June - August 2022. MMWR Morbidity and Mortality Weekly Report, 71(33), 1065 - 1068.
• National Institute of Neurological Disorders and Stroke. (2026). Motor neuron diseases.
• Tan, X., Huang, X., et al. (2011). The persistent circulation of enterovirus 71 in People's Republic of China: Causing emerging nationwide epidemics since 2008. PLoS ONE, 6(9), e25662.
• World Health Organization. (2008). Enterovirus in China. Disease Outbreak News, May 1, 2008.
• World Health Organization. (2019). Two out of three wild poliovirus strains eradicated.
• World Health Organization. (2025). Poliomyelitis.

Insights, Analysis, and Developments

Editorial Note: Enteroviruses rarely make headlines the way they did when polio wards were full, and that quiet is itself the result of decades of vaccination. Two of the three wild poliovirus strains have been wiped out, type 2 in 2015 and type 3 in 2019, but the last one is proving stubborn, with Afghanistan reporting 50 wild type 1 cases by early October 2026. The paralysis of an unvaccinated young adult in Rockland County, New York, in 2022 showed how quickly poliovirus can find a gap in coverage, even in a country that saw its last home-grown wild case in 1979. Meanwhile the non-polio viruses keep circulating with no vaccine to stop them, and for most families the practical defenses are still the plain ones: clean hands, clean surfaces and keeping childhood immunizations up to date.

Author Credentials: Ian C. Langtree is a writer, editor, and the founder and Editor-in-Chief of Disabled World, which he established in 2004 as one of the longest-running independent resources for disability news and information. Over more than two decades, he has written and edited thousands of articles on disability rights, health, accessibility, and assistive technology. Drawing on a global perspective shaped by extensive travel and lived experience, Ian is a committed advocate of the Social Model of Disability, the framework developed by disabled activists in the 1970s that focuses on removing societal barriers rather than on individual impairments. His writing is grounded in that framework and in a lasting commitment to disability rights, accessibility, and social inclusion. To learn more about Ian's background, expertise, and accomplishments, visit his full biography.