Yellow fever sidelined more US troops than enemy fire during the Spanish-American War

Dr. William Gorgas eradicated yellow fever in Panama, crucial to canal construction

The disease was one of the factors hampering the French effort to build the canal. Gorgas' experience elsewhere in the Caribbean had taught him that good drainage and quaranting patients were essential, and he would eventually apply mosquito prevention tactics on a mass scale.

Two-thirds of soldier deaths during the war were due to disease

Roughly two-thirds of all Civil War deaths resulted from disease rather than battle. Poor sanitation, contaminated water, and limited medical knowledge made camps breeding grounds for dysentery, typhoid, and other deadly infections.

Why the 1918 flu killed between 50 and 100 million people

The 1918–1920 flu pandemic (once called, incorrectly, the Spanish flu) killed quickly and in huge numbers, with estimates of the global death toll ranging from 50 to 100 million people. Several factors contributed to the high mortality rate: lack of antibiotics, the global disruption of World War I, and more.

Hughes reported on Black Americans volunteering in the Spanish Civil War

In 1937, the Baltimore Afro-American newspaper sent him to cover the Black soldiers who’d left the US to fight in the International Brigades cooperating with the Republicans in the Spanish Civil War. Hughes’ dispatches mainly focused on the racially integrated military companies, something that was prohibited in the US.

Florida reports 71 imported malaria cases annually—4% of all the US cases

The Sunshine State reports an average of 71 imported malaria cases annually. Malaria isn't endemic to Florida but mosquitoes in the state are biologically capable of transmitting the disease from one infected person to another noninfected person.

The Civil War was the deadliest conflict in American history

Between 1861 and 1865, an estimated 620,000 to 750,000 soldiers died from battle and disease—more than in all other US wars combined.

West Nile was reported in 47 states in 2025, with more than 1,400 people severely affected

Tracking numbers from the CDC indicate that the virus spread widely that year, with more than 2,000 reported human cases and many states seeing more than 25 sickened people. More than 1,400 people had neuroinvasive cases of the disease—meaning the virus had entered the nervous system, which can cause severe, potentially life-threatening illness.

From 1970 to 2017, invasive species have caused $1.28T in damage globally

The costliest species were the Asian tiger and yellow fever mosquitoes ($149B), which arrived in the US from Asia and sub-Saharan Africa, respectively. The bulk of their damage came from their transmission of diseases such as Zika, chikungunya, and dengue. (Some readers may experience a paywall.)

Europeans' arrival to America brought disease to Indigenous populations

Indigenous people lived in the Americas for centuries before the arrival of the first Europeans in the 15th century. Their arrival was disastrous for Native tribes; in addition to being enslaved and losing their land, they had no natural immunity to the diseases brought by colonists. Eventually, up to 95% of the Native American population was killed by illnesses including typhus, chickenpox, and cholera, an event now known as the Great Dying.

Approximately 180,000 African Americans served in Union forces

About 180,000 Black soldiers—roughly 10% of the Union army—served in the United States Colored Troops after 1863. Despite lower pay and discrimination, they were crucial to the Union victory.

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.

The mosquito's role in the transmission of malaria was confirmed in 1897

The British army doctor Ronald Ross, who later won the Nobel Prize for his work, was the first to describe the transmission of malarial parasites by mosquitoes. He had lab mosquitoes suck blood from malaria-infected people and separately found the malaria parasite inside a mosquito's gut, confirming the bug's role in malaria transmission.

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

Frontline traced how the outbreak started and spread across West Africa. documenting first-hand accounts and patient experiences. This Ebola outbreak was the deadliest to date, resulting in over 11,000 deaths.

The Flying Tigers: American fighter pilots who fought for China in WWII

Read the story of the Flying Tigers, a unit of American pilots, many Chinese-Americans, hired by the Chinese in 1941 to fight the Japanese in the skies. While the US wasn't officially at war with Japan until later on, some of the earliest American "victories" over the Japanese were won by the Flying Tigers. Read more of this amazing bit of aviation history here.

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

The US military, concerned about potential deployments worldwide, has long funded experimental hantavirus vaccines and therapies.

Collaborations between the military, biotech, and academic researchers led to an experimental antibody treatment for the Andes hantavirus strain—the one that more readily passes between humans. As of spring 2026, it had only been tested in animals. The US Army has also tested a potential hantavirus vaccine in people. It published early findings in 2023 that seemed promising, eliciting some immune system response. (Some users may encounter a paywall.)

Alexander the Great, Rudyard Kipling, and more may have died from food poisoning

Though it is hard to prove decades or centuries after their deaths, some researchers suspect that food poisoning killed a variety of historical figures, including US President Zachary Taylor in 1850: Some researchers believe he may have consumed food contaminated with *Salmonella*.

It took 14 years to deploy penicillin after its discovery

Despite its promise, US production of penicillin remained minimal in 1942—enough to treat fewer than 100 patients nationwide. Within two years, output expanded into millions of doses to supply troops for D-Day.

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

A wave of Latin American independence movements most likely prompted the Monroe Doctrine

Between 1810 and 1822, many Latin American colonies separated from Spanish rule, 10 in the last two years. Concerns that Spain and its European allies might try to regain these republics were a main reason behind Monroe's declaration.

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.

Explore an interactive map of battles from the American Revolution, along with detailed summaries of each engagement

Guerilla warfare was a significant part of the success of the Americans

Francis Marion, also known as the Swamp Fox, was a Patriot general who used guerrilla warfare tactics in the Carolinas during the Revolutionary War’s southern campaigns. Also called “maneuver warfare,” the approach focuses on disorienting the enemy and exploiting their weaknesses while avoiding their strengths.

Zachary Taylor became a national hero during the Mexican-American War

General Zachary Taylor led US forces to key victories in northern Mexico, earning widespread fame for his leadership. His popularity from the war propelled him to the presidency in 1848.

James Garfield's 79-day decline hooked America on news updates

After he was shot while departing Washington, DC, in 1881, the president was treated for his wounds and cared for at the White House. Since 1861, telegraphs had spanned the continent, and the Associated Press pooled sources to share telegraph news. The public, seeking updates on the president's condition, was able to receive them regularly for the first time due to this network, laying the foundation for the continuous news cycle.

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.

When German submarines lurked in US coastal waters

During World War II, German submarines (also known as U-boats) prowled the Southern coast of the US in 1942 and 1943, sinking more than 60 ships and killing 600 Allied soldiers. The campaign is less well-known, since the major battles in Stalingrad and Midway happened at the time. Several of these submarines and the ships they sank are now popular diving spots.

See a timeline of the tumultuous relationship between Cuba and the US since 1959

Only 90 miles separate Cuba from the US, yet Cold War hostility froze relations for decades. This timeline traces six decades of tension, from revolution and missile crisis to renewed hardline US policies reintroduced in 2025

The United States has had a tumultuous relationship with Cuba since its 1959 revolution, highlighted by a nuclear crisis and a decades-long trade embargo.

11 people died from firework injuries in the US in 2024.

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.

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.

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.

During the French Revolution, a botanist's letter asking about "dear Rhus" (poison ivy) was intercepted, leading authorities to suspect he was conspiring with the Russians.

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

Mark Twain spent decades feuding with the US Postal Service, convinced its costs and regulations were bureaucratic overreach.

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 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.

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

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

In 1945, Surrealist artist Salvador Dalí and legendary animator Walt Disney began collaborating on a short film that was not completed until 2003, years after both men had died.

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

Before the current East Wing ballroom project, only two White House renovations in the past 100 years cost more than $10M.

Quincy Jones' 'Big Band Bossa Nova' helped introduce bossa nova—a jazz-influenced Brazilian genre—to the US

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

Hurricanes, which rely on air consistently spinning in the same direction, cannot cross the equator because air curves in opposite directions north and south of it.

Georgia O'Keeffe's flower paintings are often assumed to be sexual, though the artist claimed she was simply interested in highlighting the beauty of flowers that most people neglect

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

Coral reefs get their colors from zooxanthellae—microorganisms that line corals' digestive tracts and provide them with sugars in exchange for a home within this protective tissue.