An enterovirus is a small, common virus that spreads mainly through contact with infected stool or respiratory droplets. Most enterovirus infections cause mild illness or no symptoms at all, but in some cases, particularly in infants and young children, these viruses can lead to serious complications affecting the heart, brain, and spinal cord. The enterovirus genus includes well over 100 types that infect humans, making it one of the most widespread groups of viruses in the world.
How Enteroviruses Are Classified
Enteroviruses belong to a large family of viruses called Picornaviridae, a name that literally means “small RNA viruses.” Each virus particle is tiny, just 30 to 32 nanometers across, and lacks an outer envelope. That missing envelope is important: it makes enteroviruses hardy. They can survive on indoor surfaces for days at room temperature and resist the stomach acid that would destroy many other viruses, which is how they successfully pass through the digestive tract.
Their genetic material is a single strand of RNA, roughly 7,000 to 10,000 nucleotides long. Human enteroviruses are divided into four species, labeled A through D. Each species contains distinct virus types that tend to cause different patterns of illness:
- Enterovirus A includes the viruses behind hand, foot, and mouth disease, such as Coxsackievirus A6, Coxsackievirus A16, and Enterovirus A71.
- Enterovirus B is the largest group. It contains the echoviruses and Coxsackievirus B types most often linked to meningitis and heart inflammation.
- Enterovirus C includes poliovirus, the most historically significant member of the entire genus.
- Enterovirus D contains Enterovirus D68, which has been tied to severe respiratory illness and a paralysis-like condition in children.
Rhinoviruses, the main cause of the common cold, are also technically enteroviruses by classification, though they behave quite differently and are usually discussed separately.
How They Spread
Enteroviruses pass from person to person, primarily through the fecal-oral route. In practical terms, this means picking up the virus from contaminated hands, surfaces, or water and then touching your mouth or face. Changing a diaper, sharing utensils, or touching a contaminated doorknob are all common opportunities for the virus to travel. Some enteroviruses also spread through respiratory droplets when an infected person coughs or sneezes, and the virus can live for hours on undisturbed skin.
Once you’re exposed, symptoms typically appear within 12 hours to 5 days. Infected people can shed the virus in their stool for weeks after symptoms resolve, which is one reason outbreaks spread easily through daycare centers and households with young children.
Symptoms: From Mild to Severe
The vast majority of enterovirus infections either cause no symptoms or produce a brief, unremarkable illness: a few days of fever, runny nose, sore throat, or a mild rash. Many adults have been infected multiple times without ever realizing it.
When enteroviruses do cause recognizable illness, the symptoms vary depending on the virus type and the age of the person infected. Hand, foot, and mouth disease is one of the most familiar presentations, producing painful blisters on the palms, soles, and inside the mouth. Other common patterns include summer colds, muscle aches (sometimes called pleurodynia when it affects the chest), and brief episodes of vomiting or diarrhea.
Serious complications are uncommon but real, and they disproportionately affect infants, young children, and people with weakened immune systems. Aseptic meningitis, an inflammation of the membranes surrounding the brain and spinal cord, is the most common severe complication. It typically causes intense headache, neck stiffness, and sensitivity to light. Most people recover fully, though it can take weeks.
Myocarditis, or inflammation of the heart muscle, is particularly associated with Coxsackievirus B types. In newborns, this can be devastating, sometimes progressing to multi-organ failure. Infants with enterovirus-related heart inflammation may also develop pneumonia, liver inflammation, and brain swelling simultaneously. Meningoencephalitis, a more serious brain infection, can cause seizures, altered consciousness, and in rare cases, lasting neurological damage.
Enterovirus D68 and Paralysis
One type deserves special attention. Enterovirus D68 primarily causes respiratory illness, often resembling a bad cold or asthma flare-up. But it has also been linked to acute flaccid myelitis (AFM), a condition in which the spinal cord becomes inflamed and causes sudden weakness or paralysis in one or more limbs. The CDC documented spikes in AFM cases in 2014, 2016, and 2018, each associated with surges of EV-D68 circulation.
AFM is rare but serious, most often affecting children. It typically begins with a respiratory illness, followed days later by sudden arm or leg weakness. In 2024 surveillance data, EV-D68 was the most frequently reported enterovirus type in the United States, accounting for 61.6% of all typed detections. Echovirus 9 was a distant second at 11.5%.
When Enteroviruses Circulate
In temperate climates like the United States, enteroviruses follow a reliable seasonal pattern. Infections are detected year-round but peak between July and September. The timing shifts by geography: southern states like Texas see their peak as early as July, while northern states like Colorado may not peak until September. Southern states also tend to have cases distributed more evenly across the year, while northern states experience a sharper summer surge.
This summer-to-early-fall seasonality is one reason enteroviruses are sometimes called “summer flu,” though they are not influenza viruses at all.
How Enterovirus Infections Are Diagnosed
Most mild enterovirus infections are never formally diagnosed. When testing is needed, typically for severe or unusual illness, the standard method is a molecular test called RT-PCR that detects the virus’s genetic material. This test can identify whether an enterovirus is present and, with additional sequencing, pinpoint the exact type.
The specimen used depends on symptoms. Stool or rectal swabs and throat swabs are the most common samples. For suspected meningitis, cerebrospinal fluid is tested. For respiratory illness linked to EV-D68, nasopharyngeal swabs are preferred. Blister fluid and blood can also be tested when the clinical picture warrants it.
Treatment Options
There are currently no approved antiviral drugs for treating enterovirus infections. Treatment is supportive, meaning it focuses on managing symptoms: fluids for dehydration, fever reducers for discomfort, and in severe cases, hospital-based care for complications like heart or brain inflammation.
Several antiviral compounds have been tested in clinical trials over the years, including drugs that block the virus from entering cells and others that interfere with viral replication. None has succeeded well enough to earn approval, typically failing due to limited effectiveness in real-world infections or unacceptable side effects. A small number of existing medications originally developed for other conditions have shown activity against certain enteroviruses in laboratory settings, but their use remains experimental.
Vaccines exist only for poliovirus and Enterovirus A71, the latter available in some Asian countries. No vaccines are available for the dozens of other enterovirus types that commonly circulate.
Prevention
Because enteroviruses lack an outer envelope, they resist many common disinfectants, including alcohol-based hand sanitizers. Soap and water is the more effective choice for hand hygiene. Regular handwashing, especially after using the bathroom, changing diapers, and before eating, is the single most effective way to reduce transmission. Cleaning and disinfecting frequently touched surfaces helps as well, though the specific products effective against non-enveloped viruses matter. Avoiding close contact with people who are visibly ill and not sharing cups or utensils during peak season further lowers your risk.