HFMD symptoms typically begin to show up 3-6 days after exposure

There are more than 200,000 cases of HFMD annually, and there's no cure

The highly contagious disease is caused by several viruses and it primarily affects little kids. It causes red spots in and around the mouth, hands, feet, and even the buttocks. They often become painful water-filled blisters that can burst and cause small ulcers. Eating and drinking is uncomfortable for about a week so patients need to be careful not to become dehydrated.

Hand, Foot, and Mouth Disease is part of the same virus family as polio

These viral infections are both caused by enteroviruses, which are a group of single-stranded, non-enveloped RNA viruses. Several different enteroviruses are known to cause this condition, including Coxsackie virus A16, Enterovirus 71, and Coxsackie virus A6.

HFMD was first reported in 1957 in New Zealand

The first clinical report involved eight kids with the characteristic sores in New Zealand, and then in the years that followed there were dozens more cases there and also reports of outbreaks in England and Scotland, among other settings, including the US.

In 2012, a virus that causes HFMD may have killed dozens of kids in Asia

More than 50 young children in Cambodia died in spring 2012 for unknown reasons, but laboratory testing of samples available from a limited number of those children came back positive for Enterovirus 71. That virus, which can cause HFMD, is known to cause severe complications among some people who contract the disease. But health officials concluded that poor baseline health and then incorrect treatment using steroids helped exacerbate their condition, helping lead to the deaths.

Hand, foot, and mouth is usually seasonal—peaking in summer—but not always

This painful, contagious disease most commonly has outbreaks in summer and early fall in the US because the enteroviruses that cause disease can most readily survive and be transmitted in warmer, humid conditions. It can still show up throughout the year, however.

Adults usually have some immunity to HFM Disease—but can still spread it

In 2025, certain eastern states including Virginia and West Virginia reported a sizable uptick in their HFMD cases, particularly in their schools and daycare centers, though the reason for the larger outbreaks remains unknown. When adults or teens get the disease, their symptoms are usually mild or even asymptomatic. Still, they may pass the disease between people, too. (Some users may encounter a paywall.)

HFMD can survive on surfaces for days at a time

That's why the virus can be transmitted via fomites—surfaces that have virus on them like doorknobs, kids toys, etc. These viruses are resilient—they are often even resistant to freezing (and are frequently stored at freezing temperatures in lab settings).

Herpangina is a related disease that also has characteristic sores in the mouth and throat

This painful condition is also caused by several viruses in the enterovirus family. The condition typically has early symptoms including a fever and sore throat, in addition to the sores. Herpangina is often mistaken for strep throat, but there's no cure for herpangina and patients typically have symptoms for about a week.

See the differences between chickenpox and hand, foot, and mouth

This helpful explainer breaks down the differences between these two contagious, viral diseases, which both present with fevers and sores. It includes photos of the sores that are characteristic of both diseases, showing how they have appeared across different skin tones to better inform people looking for information about their own loved one's symptoms.

Measles attacks the body’s immune system, leaving it vulnerable to secondary complications

A measles infection begins in the lungs, where it hijacks cells known as macrophages and begins to replicate itself. It then uses a Trojan horse method to enter the lymph nodes, where it attacks vulnerable T and B cells. Symptoms include fever and rashes.

Approximately 70% of all polio infections in children are asymptomatic

Most polio infections are asymptomatic or appear with only flu-like symptoms. Infected individuals can still shed the virus in their stool and mucus for days or weeks

About 20% of people infected with cholera have severe symptoms

That's according to studies from outbreaks in Bangladesh. Most people who contract the disease have mild or moderate symptoms, or none at all. Yet anyone infected with the disease-causing bacteria can shed the pathogens in their feces for a few days, or even up to around 10, seeding the environment with bacteria.

Every virus is classified into 7 groups based on genetic differences

Viruses infecting humans have been named based on symptoms ("chickenpox") or the location or animal in which they were first discovered ("Bolivian Haemorrhagic Fever" and "Monkeypox"). For clarity among scientists and to reduce stigma, virologists classify the 15,000 known viruses (270 of which infect humans) by their basic genetic material.

The virus was officially described for the first time in 1789

Michael Underwood, an English physician and surgeon, was the first to describe the disorder, noting it caused disability in the lower extremities in children. Large-scale outbreaks of the disease were not observed until the late 19th century.

Ebola has an average fatality rate above 50%

The Ebola virus is one of the planet’s most feared bugs. Symptoms begin with fever and fatigue but quickly develop into severe vomiting, diarrhea, and internal and external bleeding. But why is it so deadly? In short, Ebola hijacks the immune system to rapidly make replicas of itself.

Norovirus is the leading cause of food poisoning in the US

The illness is typically transmitted when virus-laden feces gets into another person’s mouth. That occurs when people do not properly wash their hands, contaminating food or surfaces.

Dengue is sometimes called 'breakbone fever' because it's so painful

Though this mosquito-transmitted disease can be asymptomatic, in more severe cases patients experience high fever, muscle spasms, and joint pain. The experience can be so excruciating that it feels like the patient's bones are broken, thus the nickname of breakbone fever. It's the world's fastest spreading tropical disease.

See the incubation periods for certain food poisoning-causing organisms

Read this chart that lists common food sources of different foodborne illness-causing pathogens and typical times between exposure and symptom onset.

Most flu cases are treated at home, but antivirals help high-risk patients

Rest, fluids and common medicines usually ease influenza symptoms. For people at higher risk of complications, doctors may prescribe antiviral drugs, which work best when started soon after symptoms begin.

Erythema migrans rash is common in Lyme—but it often doesn't look like a bull's-eye

The US Centers for Disease Control and Prevention states that this rash occurs in roughly 70% or more of Lyme disease patients, and typically occurs at the site of a tick bite. The rash may expand slowly over several days and feel warm to the touch, but it's rarely itchy or painful. As it grows, areas of it may clear—creating a target or "bull's-eye" appearance.

This real-time tracking of the hantavirus cruise ship outbreak in May 2026 offers a unique glimpse into the global reach of the outbreak and whether the virus sickened passengers and their communities around the world.

Epstein-Barr virus—the cause of 'kissing disease' mononucleosis—may be the leading cause of MS

A Harvard study with data from more than 10 million US military personnel found that people that contracted Epstein-Barr virus had a roughly 32-fold increased risk of developing multiple sclerosis. The work, published in 2022, found that Infection of the virus preceded MS onset by a median of five years, raising questions about better Epstein-Barr virus management and potential disease prevention.

Leprosy symptoms may appear 20 years after infection, so contact tracing isn't possible

The standard approach for tracking disease transmission isn't realistic for this disease because symptoms may take decades to manifest. As a result, disease transmission is still not fully understood.

Before vaccines, there was 'variolation': what was it?

Before the technology behind vaccinations was discovered, some keen observers of medicine around the globe noticed how previous infections could impact future ones. Learn about the techniques early physicians used before they had vaccines.

Between 10 million and 50 million people in the US develop rashes from poison ivy, poison sumac, and poison oak annually

If someone is exposed to one of these plants for the first time, it can take several weeks to develop a rash.

Chagas disease can be transmitted to a fetus during pregnancy

Researchers estimate that 63 to 315 cases of congenital Chagas disease occur annually in the US. Roughly 20 to 30 percent of all Chagas disease cases will progress to cardiac or gastrointestinal disease.

The 2026 Ebola outbreak is hampered by a lack of vaccine against the species of the virus, heightening the need for rapid tests to aid in disease control.

Ebola is a filovirus, meaning it resembles a thread under a microscope, though it sometimes twists and can resemble a bowl of spaghetti.

Poison ivy's characteristic rash is caused by an allergic response to an oily compound in the plant called urushiol.

Experimental hantavirus vaccines and therapies, still under development, have long been funded by the US military.

Elk Cloner, the first computer virus to spread in public, was written as a practical joke by Richard Skrenta, a Pittsburgh high school student.

Hookworm infection, though risky, may help fight certain autoimmune conditions by tamping down the immune system's inflammatory response.

See images of medical cases of firework injuries shared on this 'Instagram for doctors.' (Warning: Graphic content)

Doctors differentiate between a phobia and fear by asking patients whether their fear interferes with their day-to-day activities.

The deadliest aspect of volcanic eruptions is often not lava, but pyroclastic flows—avalanches of ash, gas, and rock that can move more than half the speed of sound.

At the beginning of the 20th century, a group of young men ate standard American food—replete with food additives like borax and formaldehyde—as part of government research to better understand food safety.

The US first hosted the World Cup in 1994, a tournament that lives in soccer infamy for its poor planning and the murder of Colombian player Andres Escobar, who'd accidentally scored on his own net.

Memecoins are a type of cryptocurrency—a form of digital currency with a wide variety of uses—created around popular 'memes,' or viral internet jokes.

When caught in the mouths of cardinal fish, seed shrimp release glowing, bioluminescent chemicals, which alert predators of the cardinal fish, prompting the shrimp's ejection.

In 1939, baseball star Lou Gehrig delivered his inspirational 'Luckiest Man' speech after retiring due to the health condition that now bears his name.

The 1987 Nintendo video game 'Stadium Events' isn't known for being particularly fun, but its scarcity has made it a highly sought-after item that has sold for up to $35K at auction.

El Niño, Spanish for 'the boy,' was named after Jesus Christ because the phenomenon resembled the weather changes observed around Christmastime.

Venture capital is a form of funding provided to early-stage companies with high growth potential, typically in exchange for an equity (or ownership) stake

Meet the 56 signers of the Declaration of Independence—most of whom didn't put pen to paper until August 2, 1776—and see their original signatures.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

The first horror movie is believed to be George Méliès' 1986 short 'The Haunted Castle,' which pioneered the use of special effects

The United States is one of only around two dozen countries with a fully federal system of government, in which power is divided between national and state governments.

The boiling temperature of water decreases with increasing elevation because the molecules need less energy to overcome the lower atmospheric pressure associated with thinner air.

The Russia-Ukraine conflict is the largest ground war in Europe since World War II in casualties, forces mobilized, and displacement of civilians.

Fast-casual restaurant Chili's is experiencing a resurgence, with its parent company recently reporting a nearly 32% increase in sales, thanks to passionate Gen Z fans on TikTok.