Wild chimpanzees have been spotted with leprosy lesions

HIV originated in Central and West Africa from a virus in chimpanzees

Researchers believe the virus crossed from chimpanzees to humans through bushmeat practices in the early 20th century, with genetic studies suggesting the most recent common ancestor of the HIV-1 M group, which is responsible for the global AIDS pandemic, emerged around 1910–1930 in Léopoldville (now Kinshasa) in the Belgian Congo.

Chimpanzees are dying from human colds

For some great apes, the threat of human-borne diseases outweighs poaching or habitat loss. This article details the danger of reverse zoonoses, which refers to diseases that spread from humans to animals.

Leprosy has been detected in British red squirrels

The animals have been infected with both strains of the bacterium that cause leprosy. Researchers have found that squirrels living in different parts of the UK were infected with different species of the disease-causing bacteria. (Some users may experience a paywall.)

People can—and have—contracted leprosy from armadillos

A 2011 study linked multiple human cases to the handling of armadillos or the consumption of their meat. The research couldn't document direct transmission, but did find that the animals and humans shared the same exact strain of the disease.

Recent research indicates leprosy was present in the Americas before European settlers

New research published in 2025 upended long-held notions that the disease was introduced to the Americas by European colonizers. Evidence of a lesser-known leprosy-causing bacterium was found in ancient human remains that date back 4,000 years.

See what regions report new leprosy cases

This graphic shows the burden of leprosy by region for 2023, based on data provided from the World Health Organization, which collates this information. Southeast Asia leads in the number of cases by region. (Some readers may experience a paywall.)

See examples of leprosy in the Bible—a broad term for skin ailments in ancient times

People afflicted with leprosy in the Bible may have had a range of different skin diseases, rather than what's clinically diagnosed as Hansen's disease (leprosy) today. In the Bible, as in many traditional societies, those with the disease were often considered unclean or sinful.

Scientists have struggled to pin down Ebola's natural reservoir species for decades, but the available evidence suggests that it's very likely fruit and insect-eating bats found in Africa.

Ebola's natural reservoir species are likely bats

But the virus doesn't seem to sicken the animals, so capturing an infected bat and performing necessary tests has remained challenging. Though many scientists believe fruit bats are the reservoir species for the virus, Ebola viral RNA fragments were detected in a greater long-fingered bat captured in 2016 in Liberia. The species isn't a fruit bat—it roosts in caves and feeds on insects. The scientist behind the discovery states that he believes the virus likely infects multiple host species and that the hosts may differ regionally. (Some users may encounter a paywall.)

Ebola species have historically been named after where they were discovered, stigmatizing residents who live there, including Bundibugyo, in Uganda.

'Sloth fever' is an emerging health threat, especially to pregnant women

This disease, caused by the Oropouche virus, is found in animals including sloths, primates, and birds. It primarily spreads through the bite of midges—insects commonly called "no-see-ums." It's endemic to the Amazon region, but US travelers are increasingly contracting it internationally.

See how Ebola tore through Guinea, Sierra Leone, and Liberia in 2014-2016.

The Chinese market for donkey hides has created a new source of diseases

Since 1992, China’s donkey population has dropped more than 80 percent. This report examines how China’s booming demand for a traditional medicine known as e-jiao, made from collagen from donkey hides, is leading to the slaughter of 6 million African donkeys annually, and providing a new source for zoonotic diseases.

Watch David Attenborough's unexpected interaction with a family of gorillas on 'Life on Earth'

On the border between Rwanda and the modern-day Democratic Republic of the Congo, Attenborough used specific vocalizations and behaviors to approach a female gorilla peacefully, only to have two of her children lie down on him. Through a comical exchange, the incident helps show the creatures to be the opposite of the aggressive, violent stereotypes about them.

In 1865, Hawaii's king authorized forcible removal, quarantining of those with leprosy

King Kamehameha V authorized the removal of anyone with leprosy symptoms and for them to be placed in a medical facility later maintained by the Catholic Church on Moloka'i, Hawaii's fifth largest island. Patients weren't allowed to transfer to other medical facilities until 1969.

Zoo animals have developed allergies, too

Although scientists do not know if allergies manifest among wild animals—and if animals can survive with them—in a zoo setting, veterinarians have observed zoo animals with common allergy symptoms, including itchiness, crusty skin, and runny eyes. Veterinarians have identified Asian elephants with pollen allergies and at least one jaguar with an allergy to fleas.

Where are humans on the evolutionary tree?

This interactive tree-shaped map explores the evolutionary connections between more than two million species. According to this map, humans are on the same branch as great apes, tarsiers, and treeshrews. That branch then splits into even smaller branches, with humans appearing on the same twig-like branch as chimpanzees and bonobos.

In 1892, two scientists purposefully infected themselves with cholera bacteria

When they became ill—one with mild diarrhea and the other with severe cholera—researchers pointed to that as proof that the pathogen caused the disease.

Lewis and Clark identified 122 animal species new to science

The Corps of Discovery recorded wildlife unknown to Americans, including grizzly bears, pronghorn antelope, and prairie dogs—offering the first detailed descriptions of the West’s diverse and often dangerous fauna.

See when the last case of wild poliovirus was found in each country

This chart shows when wild polio cases were last reported in each country worldwide. Beyond wild poliovirus, rare outbreaks can occur related to mutated strains of oral polio vaccine.

See photos of rare spotless giraffe born at zoo

A spotless giraffe was born at a zoo in Tennessee in the summer of 2023, with experts claiming the specimen is the only solid-colored animal of the species with genes for "reticulation," or the normal patchwork look. The phenomenon is so rare many...

Humanity's reduced body hair slows down wound healing

Cuts to human skin take twice as long to heal compared to chimps and other mammals. Scientists argue this is due to the reduced number of hair follicles on human bodies. Hair follicles contain stem cells which help repair skin cells faster, so as humanity shed its hair over time, so to speak, it also slowed its wound healing.

Dinosaurs suffered from cancer, arthritis, and infections seen in modern animals

Using CT scans and advanced pathology techniques, paleopathologists have identified respiratory illnesses, malignant osteosarcoma, and other diseases in dinosaurs. The research has helped show how many of these ailments are not exclusively modern phenomena.

Larger animals like giraffes, elephants, and blue whales have developed a unique defense against cancer, a phenomenon known as Peto's Paradox

Zika virus shocked scientists because the mosquito-borne disease causes birth defects

This revelation, confirmed in 2016, marked the first time that a mosquito-borne disease was known to cause birth defects. Fetuses exposed to the Zika virus during pregnancy sometimes suffer from neurological complications and microcephaly, a small-headed condition associated with neurological development issues and impairment.

The Leopold Report was an early blueprint for ecosystem management

The 1963 report, officially known as Wildlife Management in the National Parks, recommended wildlife management and ecological preservation. In 2012, a follow-up report built upon the original paper to guide future park service policies based on scientific findings.

In 1984, a dying infant lived for three weeks with a baboon heart

Pediatric-sized hearts are very hard to find. They're about the size of a walnut. When a premature baby girl was born with a fatal heart defect in 1984 her care team transplanted a 7-month-old baboon's heart into the patient. The organ was not genetically modified but still the infant lived for several weeks. This roughly hour-long documentary from the medical institution, features the patient's mother, clinician, and more discussing the controversial procedure and aftermath.

Learn how monoclonal antibodies, which mimic the body's antibodies, can fight diseases like Ebola.

Two marsupials thought to be extinct discovered in New Guinea

The pygmy long-fingered possum and the newly described ring-tailed glider were discovered in 2026 after scientists believed the species had been extinct for 6,000 years. The pygmy long-fingered possum is partially defined by its unusual trait of one finger on each hand that is twice as long as the others.

Western babies often are missing a key gut microbe common elsewhere

Studies show infants in Europe and North America often lack Bifidobacterium infantis, a microbe widespread in babies in Africa and South Asia that helps digest breast milk and train the immune system. Researchers link the gap to antibiotics, formula use, and sanitized spaces.

The American cockroach is actually from Africa, an apparent hitchhiker aboard ships carrying enslaved people, with evidence suggesting the bug may have arrived in the New World as early as the 1600s.

Poison ivy is in the same family as mangoes, cashews, and pistachios—and they all produce oily urushiol in their raw, unprocessed state—but they are typically prepared in ways to avoid causing human discomfort.

Before humans, the Soviet Union and the United States sent animals—including apes, dogs, and cats—to space during the Space Race.

The first line of 'immortal' human cells, which can divide indefinitely and are used in scientific research, was nonconsensually taken from a Black woman.

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

In 2018, 26-year-old missionary John Allen Chau was killed by tribesmen after attempting to reach and evangelize on India's isolated North Sentinel Island

The concept of phantom limbs, the perception that amputated limbs are still present, dates back to a French military surgeon in the 16th century.

See how each of the more than two million known species relates to each other—and to common ancestors—in this zoomable tree of life.

Fear or disgust related to clusters of holes and cracks, called trypophobia, may stem from evolutionary processes to help us avoid pathogens.

Many legends about George Washington, including his supposed wooden teeth and the story of cutting down the cherry tree, lack evidence.

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

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

Volcanic activity may have triggered the Black Death by spewing gases that led to crop failures in Europe, thus forcing the import of grain ships with plague-infested fleas.

An investigation suggests a Scottish island became awash in forever chemicals via seafoam and seaspray—raising questions about what that means for the safety of other coastal areas.

In 2019, a laptop loaded with six of the worst malware in history and described as 'an exhibit of historical weaponry' sold for $1.3M.

NBA superstar Victor Wembanyama spent the 2025 summer training with monks in central China to enhance his body and mind.

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

Graffiti dates back to at least ancient Pompeii, where citizens scrawled messages to one another on public walls

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.