Post-polio syndrome occurs decades after infection but isn't contagious

Paralysis from polio occurs in under 1% of infections

About 1 in 200 cases of infection causes paralysis. For paralysis to occur, the virus travels from the throat, intestines, and gut to infect specific cells within the spinal cord and brain stem that control movements. Within hours of invading the nervous system, paralysis can occur. The virus can be present in bodily secretions and stool for multiple weeks post-infection.

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

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.

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).

View this timeline of polio milestones and vaccine development

Polio has a long history in art and medicine, dating back centuries. It includes a representation of an apparent polio survivor with a shriveled leg in ancient Egyptian art. See milestones in the history of polio in this timeline.

Most polio cases today are vaccine-derived rather than naturally occuring

Weakened, live virus vaccines—which aren't offered in the US—carry a risk of virus being shed in the stool. Rarely, the shed virus mutates and leads to vaccine-derived polio infections. Most recent polio cases are genetically linked to those vaccines. As shown in this graphic, there are typically hundreds of vaccine-derived polio cases annually.

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.

After FDR was paralyzed by polio in 1921, Eleanor Roosevelt became active in politics and supported his political ambitions

FDR contracted polio at age 39 and permanently lost the use of his legs. Eleanor Roosevelt persuaded him to stay in politics, then took on the task of maintaining his public profile—attending events, building relationships, and serving as his "eyes, ears, and legs" across the country.

Chronic lyme isn't a medically recognized diagnosis in conventional medicine

It describes a constellation of symptoms attributed to a persistent Lyme infection—meaning the bacteria have remained present even after antibiotics. It often occurs among people who have never received a positive test for Lyme. Doctors do recognize "post-treatment Lyme disease syndrome," however, which can include muscle and joint pain, fatigue, and cognitive difficulties after treatment for confirmed Lyme.

The rare but deadly time bomb lurking after a measles infection

Subacute sclerosing panencephalitis, also known as Dawson disease, is a progressive and fatal neurodegenerative condition caused by a dormant measles infection. Typically, patients recover from measles normally, with the symptoms of SSPE only appearing years or even decades later. The incidence rate in unvaccinated pediatric patients is estimated to be around one in 1,300.

Long-term memory issues among West Nile survivors may be from immune response, not virus

Rodent research suggests that long-term neurological complications such as fatigue, weakness, difficulty walking, and memory loss, may be due to the immune system systematically destroying parts of neurons in the brain in response to the infection, rather than due to viral infection itself.

PTSD is a long-lasting mental disorder linked to past traumatic events

Posttraumatic stress disorder is a mental health condition arising from traumatic events with four key symptoms: intrusive memories, avoidance behavior, negative moods and thoughts, and changes in emotional and physical reactions.

Many patients with psoriasis develop other autoimmune diseases, too

A small study published in 2024 found that nearly three-quarters of patients with psoriasis—a condition in which the body attacks healthy skin cells—also developed autoimmune disorders including thyroid diseases, connective tissue diseases, and more, suggesting such connections between these autoimmune disorders warrant further exploration.

MS disproportionately sickens women, but men tend to have worse outcomes

Though the disease is more common in women, men's symptoms progress more quickly, with men more often diagnosed with progressive MS and men's cases typically resulting in more severe symptoms—perhaps due at least partly to more delayed diagnosis—and more severe disability over time.

Five to ten percent of Alzheimer's cases are early-onset

Early-onset Alzheimer’s typically emerges around 40 to 50 years of age, with devastating effects. This video follows Brian, diagnosed with the disease at age 54, as he travels the country as an advocate for research and discusses the progressive mental fog of Alzheimer’s.

Food poisoning can sometimes cause serious long-term health issues

Although foodborne illness can be relatively mild and cause short-term discomfort, more rarely it can also cause long-term severe health consequences, depending on your individual risk factors, the severity of your sickness, and the care you receive. Kidney failure is one serious complication associated with certain types of food poisoning. Meningitis, hepatitis, arthritis, and pancreatitis are also rare and serious foodborne illness complications. If a pregnant person gets food poisoning, it can cause health issues for the fetus.

Perceived isolation ages you

Mounting evidence suggests that socialization is a vital component of maintaining good health. Research published in 2024 from Mayo Clinic researchers analyzed the social lives of more than 280,000 adults and concluded that individuals that weren't likely to participate in extracurricular social activities and get-togethers were more likely to have a biological age older than their actual age—meaning that you may be 60 but health indicators would suggest you're older.

The hormonal disorder PCOS was renamed PMOS in 2026, a move designed to improve care and research by shifting the focus to the hormonal causes of this condition that affects 1 in 8 women.

In 2011, a mysterious illness spread around LeRoy, New York

A handful of girls were stricken with bizarre twitches, tics, and spasms — all apparently involuntary. Some believed the incident to be conversion disorder, an illness where emotional troubles have physical symptoms.

Bill Nye did not have children for fear of passing on ataxia

In his 2017 documentary, Nye revealed the congenital, neurological condition on his father's side of the family, which is characterized by a lack of balance and problems with fine motor movement. He has since learned he likely does not have the disease, though both his siblings have shown symptoms.

Postmenopause is a stage lasting roughly a third of a woman's life

Postmenopause is the final stage of menopause, occurring once a woman hasn't had any bleeding for a full year. She is then considered postmenopausal for the rest of her life. While some of the intense symptoms she might experience during perimenopausal will decline, her risk for certain conditions and diseases will increase.

Research suggests the brain maintains connections to lost limbs

Decades-old research suggested brain reorganization after amputations, but brain scans show unchanged limb representations. Phantom limb pain may result from such unchanged brain maps, which may enhance prosthetic limb control in brain-computer interface technology.

Healthy adults should perform 'progressive resistance training'

That's the recommendation in March 2026 from the American College of Sports Medicine. They reviewed existing studies on the topic and concluded that resistance training with progressively more weight and repetitions improves muscle strength, size, power, endurance, gait speed, balance, and more.

PIckleball's popularity with seniors is partially due to its health benefits

Pickleball has always been a game for all ages, but it has been particularly popular among seniors, in part because of its many health benefits, including enhancing hand-eye coordination and burning more calories than walking.

Type 1.5 diabetes is typically found in adulthood

Clinically referred to as latent autoimmune diabetes in adults, or LADA, this condition is often diagnosed as Type 2 diabetes. However, it’s an autoimmune disease that eventually requires insulin, just like Type 1 diabetes. Misdiagnosis can result in uncontrolled high blood sugar and a slew of other serious health issues.

Recent research found that the brain doesn't seem to massively rewire following amputation—upending earlier beliefs about the cause of phantom limb pain.

There is no cure for the general condition of arthritis

While there are innumerable conditions ultimately leading to the joint pain we collectively term "arthritis," one common pathway is progressive inflammation and joint damage many years after an injury.

Urushiol, the oily toxin in poison ivy, can remain allergenic on clothing for years.

About 12.5% of US adults experience a phobia in their lifetime, a diagnosis that hinges on the intense fear interfering with daily life and persisting for at least six months.

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

Listen to an in-depth conversation on the links between Parkinson's disease and herbicide exposure and the challenging pace of scientific investigation.

Coral polyps reproduce via broadcast spawning, where entire reefs simultaneously release reproductive cells for about one hour, once a year.

Indefinite cloning of some endangered species may not sustain their longevity because cloning success rates decrease as genetic mutations accumulate.

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

Firework or sparkler burns, even if they cover a relatively small area of skin, can significantly affect our range of motion.

An Ebola vaccine was developed during the 2018 west African Ebola outbreak, but the 2026 Ebola outbreak is with a different species of the virus, not the one that the vaccine is approved to treat.

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

The US Constitution is widely regarded as the longest-standing written national constitution still in force—see how it has influenced rights worldwide.

A pickleball's loud 'pop' sound can reach 120 decibels, which is equivalent to a hammer hitting a nail

Some renewable energy sources may weaken the resiliency of electric grids by removing outage buffers provided by coal- and natural gas-fired plants, which provide the system with more time to find a new power source if a plant goes down.

Domino's Pizza's 30-minute delivery guarantee was responsible for the chain's 1980s surge, but it was discontinued after the company was found liable for delivery driver accidents.

The USPS spent $3.97B in 2024, accounting for .058% of the federal budget.

The distributor behind 'Rocky Horror' pulled the film from its scheduled national release, believing it would be a failure, though it eventually amassed a dedicated fanbase through midnight showings, a trend that continues over 50 years later.

In 2026, Finland was named the world's happiest country for the ninth consecutive year based on its wealth, social safety network, and high life expectancy, among other factors.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

Frank Lloyd Wright's houses are historically hard to sell because they're old, subject to local landmark commissions, and often unfashionable

Dozens of S&P 500 stocks, including Coca-Cola and Walmart—known as the dividend aristocrats—have increased dividends every year for 25 years

In 2025, four executives from large tech companies were given positions in the US Army Reserves—including Palantir Chief Technology Officer Shyam Sankar, which reinforced Palantir's ties with the US military and its role as a leading defense partner.

View the ten deadliest tornadoes in US history.

In 2009, the nation was gripped by the story of a missing young boy who was believed to be floating over Colorado in a homemade balloon, until it was revealed that he was at home the whole time.