Malaria case in Maryland stumped doctors in 2023—leading to the wrong treatment

10 locally acquired malaria cases were reported in the US in 2023—a surprise

The cases, reported in Florida, Texas, Maryland, and Arkansas, broke a 20-year streak since there had been no reported locally acquired mosquito-transmitted malaria in the country since 2003, when there was a case in Florida.

Untreated malaria can lead to blocked blood vessels in the brain, coma, and organ failure

Malaria is treatable with medications, but sometimes even after treatment, infection can come back because the disease-causing parasite wasn't completely eliminated. Patients may also have symptoms that emerge years after the initial infection and treatment.

Maryland required cholera researchers to fly a yellow warning flag—signifying quarantine dangers in the 1970s

University of Maryland Hospital researchers intentionally infected volunteers with the cholera bacterium in the late 1970s to further their understanding of the disease. They proceeded with this work following the recommendation of a US government panel. (Some users may encounter a paywall.)

Hear what it's like to have malaria

In Kenya, as one malaria-sufferer explains, the disease is common enough that anytime a child has a fever or any sort of sickness families and the community will wonder if it's malaria. Sleeping under a mosquito net is recommended. Unfortunately, a gin and tonic will not keep malaria at bay.

A French Army surgeon discovered that malaria is a parasitic disease in 1880—but scientists were initially skeptical

Charles Louis Alphonse Laveran won the Nobel Prize for his work "on the role played by protozoa" in causing diseases. His work included discovering and reporting the malaria-causing parasite in the blood of a patient suffering from malaria.

Anopheles mosquitoes are developing resistance to insecticides

The malaria-transmitting mosquito species is developing resistance to the insecticides used in insecticide-treated bed nets and in indoor spraying in people's homes and communities. Malaria parasites are also developing resistance to antimalarial drugs.

Nonwhite Lyme patients tend to be diagnosed later and have more severe disease

Peer-reviewed research published in 2025 from Pfizer—a pharmaceutical company working on a candidate vaccine for Lyme disease—examined Lyme data from more than 150,000 Medicare and Medicaid beneficiaries and found that Black patients, as compared to white beneficiaries, were more likely to have disease that had spread further throughout the body at the time of care. The difference, the scientists wrote, may be partly due to difficulties recognizing the characteristic rash on darker-colored skin.

Yes, many animals get malaria—not just humans

Birds, rodents, monkeys, lizards, bats, apes, and livestock are among the species that can become infected with malaria. Infected animals' symptoms often resemble those of humans, including fever, lethargy, loss of appetite and difficulty breathing. Birds will also have ruffled feathers and drooped heads.

See this diverse list of vector-borne diseases

Human illnesses caused by parasites, viruses, and bacteria, and transmitted by a living organism—often small, bloodsucking ones like mosquitoes, ticks, and sandflies—are known as vector-borne diseases. That carrier is called a vector. These diseases disproportionately affect the poorest populations in tropical and subtropical areas.

Search Lyme disease incidence in your county

The searchable database at the bottom of this webpage allows users to check the reported incidence of Lyme disease in US counties and Canadian health regions. In 2022, for example, Baltimore County in Maryland had a rate of about 34 probable and confirmed cases per 100,000 people. Arlington, County in Virginia was less than half of that for the same time period.

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.

Molecular evidence suggests the deadliest malaria parasite may be 100,000 years old

Plasmodium falciparum, the form of the parasite that kills the most humans, may date back 100,000 years, according to mitochondrial DNA analysis published in Science in 2003. It suggests that the parasite took off in humans about 10,000 years ago.

Most penicillin allergy diagnoses are wrong

A Freakonomics Radio episode investigates why so many people mistakenly believe they’re allergic to penicillin. This widespread misdiagnosis leads to costlier, less effective treatments and contributes to the growing problem of antibiotic resistance.

How a scientist discovered West Nile is spread by birds

Listen to Tracey McNamara, former chief pathologist at the Bronx Zoo, detailing her surprising late 1990s discovery that established West Nile virus is spread by birds. Financing animal disease surveillance studies, she says, saves human lives and surveillance gaps may fuel missed opportunities to identify dangerous diseases before they jump between species.

Health problems are being misdiagnosed as perimenopause symptoms

Symptoms of menopause and perimenopause (the premenopause period) can be varied enough that clinicians dismiss them in patients in their mid-30s and onward as just a symptom of hormone level change. In this story, a woman's itching was dismissed as a hormonal change, but after two years and 11 separate doctor consultations, was diagnosed as cancer. (Some users may experience a paywall.)

The history of germ theory, which explains that illnesses are caused by microorganisms

For centuries, the miasma theory, which held that illnesses were caused by clouds of "bad air" produced by decaying organic matter, was the accepted explanation for the spread of disease. The development of microscopes and the subsequent technology to isolate bacteria and test disease spread in mice greatly contributed to contagionists overturning miasmatists.

More than half of the 7,000 'kissing bugs' locals sent to Texas A&M University had parasites

Texas A&M University scientists began a community science program in 2012 asking people to send in kissing bugs (any of the 11 species of bugs potentially infected with Trypanosoma cruzi parasites). About 1,500 people sent in over 7,000 bugs for scientific research, and about 55% of the bugs were infected with the parasite that causes Chagas disease.

Watch the safe way to remove a tick from your body

Minimizing your risk of Lyme and other tickborne diseases hinges on quickly removing ticks. To do so, place tweezers on the animal as close to the skin as possible and then pull directly upwards to try to avoid leaving bits of the tick's body behind. If possible, try to take a photo of the tick to share with your doctor to better identify potential disease risks (since certain tick species can carry specific diseases). Next, dispose of the tick without crushing it in your fingers—flushing it down the toilet, or placing it in alcohol or a sealed bag—and then thoroughly wash the bite area and your hands.

Ticks survived 27 years in a lab, including eight without food

Research published in 2022 set a new record for tick longevity. A group of adult African ticks that are normally found in eastern and southern Africa lived in a laboratory for 27 years, including eight without food. What's more, one of the females laid eggs at least four years after the last male died. Most ticks, on average, reportedly live for six months to three years.

'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 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.

A moldy cantaloupe supercharged penicillin production

In 1943, a moldy cantaloupe found at a market in Peoria, Illinois, yielded a strain that produced six times more penicillin. Though often credited to lab worker “Moldy Mary” Hunt, accounts differ on who actually brought in the fruit.

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

Clinics in the Democratic Republic of Congo saw patients with Ebola symptoms months before the disease was identified. The identification lag was due to inadequate diagnostics that could not accurately or quickly identify the virus's myriad species. Contact tracing and better diagnostics will be required to tamp down the outbreak.

Ménière's disease was first identified in 1861

This condition is named after the French clinician Prosper Ménière, who first identified it as being linked to the inner ear, noting it was a disorder of the semicircular canals. It tends to occur in people who are 40 years old or older.

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.

How the most famous Ebola book, The Hot Zone, which sold 3.5 million copies and was translated into 30 languages, got aspects of the disease so wrong.

Marburg virus, related to Ebola, is also extremely deadly, and has no available vaccine.

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.

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

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.

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.

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

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

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

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

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.

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

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

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.

Abraham Lincoln was almost assassinated weeks before his inauguration as he traveled from Illinois to DC through Baltimore in 1861; it took two independent claims for Lincoln to be convinced the threat was real

View the ten deadliest tornadoes in US history.

The story of Dollree Mapp, whose legal challenge over her 1957 conviction for possessing "obscene material" led to a major strengthening of the Fourth Amendment

Some Pokémon have been named after real and fictional organisms, while some real-world species have been named after Pokémon, such as Chilicola charizard and Binburrum zapdos.

Budweiser stores yeast derived from the original 1800s strain in a secret bunker, which only the Head of Yeast Management can access—not even the CEO

The Dracula character, now seen as the vampire archetype, was inspired by a seafood-induced nightmare its creator experienced.

Radioactive elements can introduce software errors because the ionizing radiation they produce can detach electrons from atoms, and computer code relies on the distribution of electrons.

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

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

Clever Hans was a 1900s horse that was believed to be able to solve math equations, tell time, and read and comprehend German, until a psychology student discovered how he got his answers.

Despite being favored by 87% of Americans, Congress does not have term limits.