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

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.

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.

Hand, foot, and mouth disease spreads easily—including via fomites

The common ailment spreads through respiratory droplets, touching infected secretions like poop, but also by touching virus-laden fomites, which are contaminated objects such as doorknobs or toys.

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.

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

Fever is often the first symptom and then painful sores may develop a day or two later. Coxsackie A16 is currently the most common enterovirus that leads to the disease, though there are several other enteroviruses that can cause it as well.

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 colorized mpox virus particles grown in culture at Fort Detrick, Maryland, where high-biosecurity pathogens are studied.

The similarly named foot-and-mouth disease doesn't affect humans, unlike HFMD

Though the names are similar, foot-and-mouth disease—also known as hoof-and-mouth disease—exclusively affects animals, primarily those with hooves, such as cattle, sheep, pigs, goats, and even giraffes. It doesn't sicken humans, though both this disease and hand, foot, and mouth disease do come from the same family of viruses—Picornaviridae.

Foot-and-mouth disease, which affects animals, has been eradicated in many locations

The disease, which causes fevers and painful blistering in the mouth, muzzle, snout, teats, and feet—somewhat similar to hand, foot, and mouth disease in people—is transmitted via contact with infected animals or their fluids or eating infected foods or meat. Though it primarily affects cloven-hoofed animals, it's also been known to sicken camels and even elephants.

CDC does not require docs to report hand, foot, and mouth cases which makes tracking difficult

Mid-Atlantic states saw a surge of hand, foot, and mouth disease in 2025 for as-yet unknown reasons. Virginia, Maryland, and New Jersey, reported elevated outbreak numbers in 2025 as compared to other recent years, but since the US Centers for Disease Control and Prevention does not require mandatory reporting of positive HFMD cases—unlike strictly notifiable diseases like measles—it's hard to truly know the extent of the outbreaks and how significant the caseload is as compared to prior years across the region or country.

Mpox, formerly known as monkeypox, does not come from monkeys but it was first identified in laboratory monkeys in 1958.

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.

Polio commonly spreads when virus-laden feces gets into our mouths

This highly infectious disease is transmitted from one person to another, mainly when we eat virus-laden poop particles. Less frequently, contaminated food or water can transmit the virus, or people can be infected via respiratory droplets (from coughing or sneezing).

Breaking down the different types of vaccine technologies

There are several different types of vaccines. Each type is designed to teach your immune system how to fight off germs—and the serious diseases they cause. This short overview breaks down the differences between the types.

Eczema appears to heighten the risk of developing shingles.

Variola: the second-deadliest virus on Earth

Because it was declared eradicated in 1980, many forget smallpox is one of history's deadliest diseases—in its final century, it's estimated to have claimed 500 million lives. This 11-minute video from production studio Kurzgesagt takes a look at...

'Tomato flu' outbreak in India turned out to be HFMD

An illness initially dubbed "tomato flu" in 2022 that sickened children in Kerala, India, with symptoms typical of hand, foot, and mouth disease turned out to be that—not a new ailment. A letter published in the prestigious journal The Lancet had initially described the illness as "a new virus" but at least some of the children ultimately tested positive for one of the viruses that causes HFMD, so it wasn't a new condition after all. (Some users may encounter a paywall.)

Measles symptoms range from fever to pneumonia and encephalitis

While less common, most measles-related deaths come from secondary conditions such as pneumonia (one to six cases per 100 patients) and encephalitis (one case per 1,000 patients). Blindness, which is rare, may arise from corneal ulceration.

Secondary complications from measles in children range across the whole body.

Although rare, HFMD can spreads in pools due to poor bathroom hygiene

In pools with inadequate levels of chlorine, this disease can spread via the poop-to-mouth route, though this isn't one of the most common ways the disease is transmitted. People can become infected by swallowing contaminated pool water after little kids (or their parents) don't do an adequate job removing virus-laden feces from the child before the child enters the water.

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.

Measles infection, which was nearly universal during childhood in prevaccine era, was described by the Persian physician Rhazes in the 10th century as "more to be dreaded than smallpox."

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

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.

At least 7 eastern college campuses experienced surprisingly large HFMD outbreaks in 2018

The outbreaks at the college level caused a particularly nasty set of symptoms, including the usual blisters in the mouth and on the hands and feet—but also affected the genitals. They surprised health officials who weren't sure why so many young adults were being sickened, including more than 120 kids at Johns Hopkins University. The disease also caused outbreaks at campuses including Princeton, Dartmouth, West Virginia University, Lehigh University, Wesleyan University in Connecticut, and Mars Hill University in North Carolina.

There have been close to 40 Ebola outbreaks since 1976

Ebola is a rare but deadly virus that causes severe illness, organ damage, and sometimes internal bleeding. It spreads through contact with infected bodily fluids and is most common in parts of sub-Saharan Africa. This explainer covers its symptoms, transmission, and treatment options.

Leprosy affects the skin, eyes, and upper respiratory tract

Untreated, the disease can lead to permanent nerve damage and the loss of sensation in arms, legs, and other extremities. The exact form of transmission remains unclear, but scientists suspect it is spread via respiratory droplets over a prolonged period. (Warning: Graphic content, including photos of deformities.)

Live virus vaccines predated polio—that's how we vaccinate against smallpox

Since 1796, smallpox vaccines have used a live poxvirus related to smallpox. Yellow fever vaccines have used a live weakened form of the virus responsible for yellow fever since 1937.

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

See if you know how to recognize poison ivy with this quiz.

Improved 19th-century sanitation meant kids encountered polio later, with worse results

Almost all children likely used to contract poliovirus, but scientists suggest that when infants encountered it very early in life—due to poorer conditions and hygiene—they still had some maternal protection from pregnancy or through breastmilk, so the symptoms were more flu-like.

There’s a lot we still don’t know about goose bumps in humans

Though goose bumps can be associated with changes in skin temperature, the biggest gaps in our understanding are around measuring goose bumps from nonthreatening exposures. These bumps can often occur without our detection, and we have trouble correctly identifying them. The relationship between emotionally induced chills and goose bumps can also be tenuous.

Explore these images to better understand why food poisoning makes you feel nauseous.

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.

Goose bumps require a surprisingly complex series of steps

Watch an anatomical breakdown of how goose bumps work—featuring real skin from a human cadaver, a segmented brain, and a detailed anatomical model of the skin—to learn about all the jargon behind goose bump science. (Warning: Includes graphic footage of cadaver skin.)

See how cholera spreads in a community

This animated video offers a comprehensive look at how cholera spreads. It makes clear why it's so difficult to stamp out this disease in communities around the world. It also details what steps can help control cholera.

What are zoonotic diseases?

Interspecies interactions are a breeding ground for disease transmission. This basic background information on zoonotic disease from the Centers for Disease Control and Prevention (CDC) chronicles the different ways humans can get sick, identifies what groups are particularly vulnerable, and offers links to other resources.

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.)

Explore a technical look at the measles virus and its toll on humanity through the ages.

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

A rare measles complication is that the virus can linger in the body for years after apparent recovery and continue to replicate—leading to a progressive and fatal breakdown of the central nervous system that can occur decades after the initial infection.

Learn about the basic anatomy of mosquitoes

This short explainer video breaks down the mosquito's general body components, highlighting how mosquitoes breathe, fly, and more. It also touches on how experts can tell different mosquito species apart.

Leprosy doesn't cause fingers or toes to fall off

The nerve damage that results from infection sometimes causes loss of feeling in extremities so injuries like cuts or burns may be missed. In such cases, resulting infections can lead to digit loss. Fingers or toes can also appear to shorten with this disease because nerve damage can sometimes make muscles in fingers and toes so weak that they're reabsorbed by the body.

Explore a 3D model of the influenza virus

This interactive 3D model reveals the influenza virus’s structure—its outer coat and spike proteins—and compares it with other well-known viruses, offering a clear view of how flu differs from pathogens like HIV or coronaviruses.

Poison ivy's rash-causing compound is found in the plant's roots, stem, and leaves—so coming into contact with any part of the plant can lead to rashes for the 85% of people who are allergic to it.

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.

The oral, live virus vaccine is the most robust but carries more risks

The live virus vaccine, delivered via oral drops, induces the best protection in the body. Because it includes a live, weakened form of the virus there's an extremely small risk it can sicken recipients and potentially cause paralysis. Recipients also shed the virus in their stool, which can rarely lead to vaccine-derived cases of the virus if the virus mutates. (Some users may experience a paywall.)

Ebola is a filovirus, meaning it resembles a thread under a microscope.

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

This is what happens inside your body when you're sick

This video details the biology of what happens inside the human body during illness.