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.

The US won every major battle of the Mexican-American War

Despite being outnumbered in key engagements, US forces defeated Mexican armies across every major front. Superior training, leadership, and logistics allowed the US to win decisively—capturing Mexico City without losing a single major battle.

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

European diseases killed a massive share of the Native American population

After Western contact, epidemic diseases devastated Indigenous communities. By 1920, the Native American population of the US had fallen to roughly 270,000, compared with an estimated 1.2 to 18 million at the time of European arrival.

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.

Wolbachia: the bacteria that could eliminate dengue fever

Dengue fever, transmitted by mosquitoes, kills more people annually than all types of natural disasters combined. However, mosquitoes that host Wolbachia bacterium have their ability to transmit the virus naturally suppressed, offering a route to eliminating nearly 25,000 deaths annually.

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.)

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.

West Nile Virus has been detected in American alligators, and outbreaks have led to substantial economic losses on alligator farms.

A malaria case in Maryland stumped doctors in 2023—leading to the wrong treatment and underscoring the challenge of physicians being mindful of tropical diseases in our interconnected world.

US troops committed widespread atrocities during the Mexican-American War

American volunteer regiments frequently looted towns, raped civilians, and executed prisoners—especially in occupied northern Mexico. Historians have documented how racial hatred and impunity fueled war crimes that were rarely punished by military leadership.

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.

How the 1918 pandemic spurred developments in virology and vaccines

This article provides an in-depth historical account of the 1918 Spanish Flu pandemic, including its impact on the global population and how its occurrence spurred significant advancements in the study of viruses—laying the groundwork for the...

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.

US West Nile case numbers were up 40% in 2025 across the United States though theories vary to explain this surge.

More than 20 mosquito-borne and tick-borne diseases are found in the US

Children, older adults, and people with compromised immune systems are at particular risk of poorer health outcomes from these diseases. But dog owners and outdoor enthusiasts are among those at particular risk of contracting these illnesses, which include Lyme disease, Zika, and the condition Alpha-gal Syndrome.

Hollywood's efficient response to the Spanish flu made it a filmmaking destination

In 1918, the Great Influenza epidemic killed more than 675,000 Americans. Los Angeles was one of the first cities to shut down movie theaters, most of which were independently owned and couldn’t afford the revenue loss. The results were twofold: the quick response meant that Hollywood could bounce back faster than other film hubs, and it also contributed to the rise of vertical integration as studios stepped in to purchase the flailing theaters.

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.

More than 58,000 American soldiers died in the Vietnam War

Fought to contain communism in Southeast Asia, the Vietnam War became one of the most costly and controversial Cold War conflicts. The US ultimately withdrew in 1973, and South Vietnam fell to communist forces two years later.

The Spanish flu had a major impact on the 1919 NHL season

Just two years after the National Hockey League was officially formed, its champion was playing the PCHA champion for the Stanley Cup. The series was tied, going into the deciding Game 5, when all but three NHL players fell ill with the Spanish flu. No champion was crowned that year.

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

Ebola virus, with an average fatality rate of around 50%, has been responsible for more than 2,000 confirmed deaths during the 2026 outbreak in the Democratic Republic of the Congo and Uganda.

How we helped make Aedes aegypti mosquitoes such a problem

Mosquito genome sequencing data suggests that Aedes aegypti mosquitoes first started specializing on human blood around 5,000 years ago—when climates shifted and humans started domesticating plants in Africa and stored large amounts of water that may have attracted the bugs.

Penicillin ended scarlet fever’s deadly threat to children

Between 1840 and 1883, scarlet fever was among the leading causes of childhood death in the United States, with case fatality rates ranging from 15% to 30%. Today, thanks to antibiotics like penicillin, the mortality rate is below 1%.

Measles reached global transmission during the 15th- and 16th-century Columbian exchange

Devastating diseases like smallpox, influenza, measles, and other viruses were largely introduced into the Western Hemisphere beginning with the 1492 arrival of Christopher Columbus and the ensuing age of exploration.

West Nile Virus is maintained in nature, even without human infections

Mosquitoes pick up the virus when they feed on birds, and then pass it to other birds with their bite, delivering it via virus-laden saliva. Hundreds of different North American bird species can harbor the virus—even if they don't all get sick from it.

Human records of influenza stretch back more than two millennia

Accounts of flu-like illness appear as early as 412 BCE, when Hippocrates described a sudden wave of cough and fever. Centuries of recurring outbreaks culminated in the first clearly documented pandemic in 1580, spreading from Asia into Europe and Africa.

Human records of influenza stretch back more than two millennia

Accounts of flu-like illness appear as early as 412 BCE, when Hippocrates described a sudden wave of cough and fever. Centuries of recurring outbreaks culminated in the first clearly documented pandemic in 1580, spreading from Asia into Europe and Africa.

View animated battle maps from every major skirmish of the American Civil War.

Wolbachia is also being used to slash mosquito numbers

The naturally occurring bacterium does not naturally infect Aedes aegypti mosquitoes, but communities in locations including California and Texas have released male mosquitoes infected with Wolbachia and reported a significant drop in subsequent mosquitoes: When infected males mate with uninfected wild females, the eggs don't hatch.

Penicillin slashed battlefield pneumonia deaths during World War II

Before antibiotics, bacterial pneumonia killed about 18% of infected soldiers in World War I. By World War II, penicillin cut that death rate to less than 1%.

Wolbachia is a naturally occurring bacterium being employed to fight dengue

Scientists are fighting dengue spread in a roundabout way: injecting bacteria into Aedes aegypti mosquito eggs, which blocks the dengue virus from replicating in the tissue of mosquitoes. Researchers hope the bacterium will be passed to future generations, inoculating them against dengue. Wolbachia is also being investigated to combat other mosquito-borne diseases.

Nearly 5,500 crows died during four months in 1999 from West Nile in NYC.

Explore inside a mosquito factory where millions of mosquitoes are bred weekly

In Medellin, Colombia, scientists are infecting Aedes aegypti mosquitoes with Wolbachia, a bacterium that wouldn't otherwise infect the species, but does block its ability to transmit dengue, Zika, yellow fever, and chikungunya. In the wild, infected mosquitoes would breed with wild mosquitoes, pass down Wolbachia, and thus reduce disease transmission.

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

The Mexican-American War trained future Civil War generals

Many key military leaders of the Civil War—including Ulysses S. Grant, Robert E. Lee, and Thomas “Stonewall” Jackson—first saw combat in the Mexican-American War, gaining battlefield experience that shaped their later commands.

Irish immigrants deserted the US Army to fight for Mexico

During the Mexican-American War, hundreds of Irish Catholic immigrants—facing discrimination in the US Army—defected to Mexico and formed the Saint Patrick’s Battalion. Though many were captured and executed, they remain honored as heroes in Mexico.

Treating black fever can result in a complication that spreads the deadly disease

Black fever, a deadly parasitic disease second only to malaria, threatens more than 1 billion people across more than 83 countries. Also known as kala-azar or visceral leishmaniasis, the disease is caused by parasites that spread through sandfly...

Lyme disease is the most common vector-borne illness in the US

In the US, ticks account for 90% of all disease transmission from bites, including mosquitoes. And Lyme disease is the most common vector-borne disease in the US overall, with estimates suggesting there are about 475,000 Lyme cases annually across the nation.

'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.

Mosquitoes top the ranking of the world's deadliest animals.

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.

See how Ebola tore through Guinea, Sierra Leone, and Liberia in 2014-16.

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.

A novel H1N1 influenza strain sparked a 2009 global pandemic

First detected in Mexico, the 2009 “swine flu” pandemic infected up to 1.4B people worldwide. While mortality rates were lower than earlier pandemics, the outbreak still caused more than 150,000 deaths.

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.)