Explore this interactive visualization of illnesses known to jump from animals to people, and learn how these zoonotic diseases spread.

Zoonotic diseases: Pathogens that jump from animals to humans

Such diseases may be caused by a variety of pathogens—viruses, bacteria, fungi, or parasites—and can originate in creatures ranging from ticks and mosquitoes to pigs and bats. Because they develop in animals and are often new to human immune systems, zoonotic diseases have severe consequences for public health.

What are zoonotic diseases?

Interspecies interactions are a breeding ground for disease transmission. This basic background information on zoonotic disease from the Centers for Disease Control and Prevention (CDC) chronicles the different ways humans can get sick, identifies what groups are particularly vulnerable, and offers links to other resources.

Watch how viruses like Ebola can spill over from animals to humans—and vice-versa.

Animal-to-human pathogens constitute 75% of emerging infectious diseases

Zoonotic diseases encompass more than 200 diseases transmitted from animals to humans, wherein humans are usually accidental hosts. Ranging from rabies to HIV to monkeypox, this overview lists some of the most common viral threats.

Climate change is influencing the spread of disease

Rising temperatures and water levels are forcing animals and pathogens beyond their typical boundaries. This article and its data visualizations explore the proliferation of climate-driven diseases.

Increasing contact between humans and wild animals is driving zoonotic threats

Zoonotic diseases, which spread from animals to humans, present one of the most significant emerging threats worldwide. Scientists have identified around 200 viruses capable of infecting humans, and unfortunately, the number of such diseases are on the rise—at least 60% of all emerging infectious diseases are zoonotic in origin.

Vector-borne diseases kill more than 700,000 people globally each year—and are growing

The diseases with the greatest potential to spread widely aren't the ones that quickly kill human hosts. Instead, the best hosts or reservoirs for vector-borne diseases would be chronically ill over the long term, increasing the likelihood that the pathogen could be transmitted to others.

Bats are uniquely suited to act as reservoirs of viruses.

Some of the deadliest diseases to jump from animals to humans originate in bat species. This rich visualization explores the diversity of bats and the factors that make them efficient vectors for harboring and transmitting disease, from their long lifespans to their migration patterns.

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.

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.

A timeline of major pandemics from 1899–2025

Modern pandemics have been defined by the race between globalization (which increases risk) and the development of new medicines. The Great Influenza epidemic claimed some 50 million lives, and the COVID-19 pandemic killed more than 7 million. In between, diseases like Ebola, cholera, AIDS, and more have devastated communities.

A heatmap showing the drop in infectious diseases post-vaccine deployment

The number of infected people, measured over 70-some years and across all 50 states and the District of Columbia, declined significantly after vaccines were introduced.

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.

Rabies kills more than 50,000 worldwide each year

Rabies transmission to humans typically comes from an infected animal, and death was very common before recent protocols were developed (post-exposure prophylaxis). The virus is neurotropic, which means it has an affinity for nerve tissue, and moves quickly from broadly infecting the body to destroying the brain.

Every virus is classified into 7 groups based on genetic differences

Viruses infecting humans have been named based on symptoms ("chickenpox") or the location or animal in which they were first discovered ("Bolivian Haemorrhagic Fever" and "Monkeypox"). For clarity among scientists and to reduce stigma, virologists classify the 15,000 known viruses (270 of which infect humans) by their basic genetic material.

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.

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.

Scientists found that if cats ate infected rodents, they could get West Nile in lab experiments.

Visualizing the genetics of SARS-CoV-2

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, began with an outbreak in Wuhan, China in December 2019, and rapidly spread worldwide in early 2020. On March 11, 2020, the World Health Organization declared COVID-19 a global pandemic, leading to widespread lockdowns, travel restrictions, and economic disruptions.

See how cholera spreads in a community

This animated video offers a comprehensive look at how cholera spreads. It makes clear why it's so difficult to stamp out this disease in communities around the world. It also details what steps can help control cholera.

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

Explore 3D models of some of the most dangerous viruses, allowing us to understand these and other pathogens in new ways.

Interactive human migration map

Using archeological, genetic, and climate data, scientists have pieced together an outline of the human odyssey—the journey that took our species from Africa to all corners of the globe. Experience this 200,000-year migration using an interactive human migration map.

Measles evolved from an ancient cattle disease, branching off as recently as 3,000 years ago.

Seven known types of coronaviruses have jumped from animals to humans

Coronaviruses, including SARS-CoV-2, belong to a large family of viruses characterized by their crown-like appearance under a microscope, due to spike proteins on their surface. While thousands are believed to exist in animals, only seven are known to have made the jump to humans.

Watch an expert's take on the rare disease hantavirus—and why it's not of great concern to the general population

This rare zoonotic disease, transmitted to humans primarily through infected rodent droppings, urine, or saliva, is rarely spread between people. The disease was of particular concern in spring 2026, when an outbreak occurred on a 150-person cruise ship, prompting a flurry of action, including contact tracing for passengers in their home countries. The disease can be fatal. But early care—primarily oxygen support—can help patients survive.

Using mosquitoes to vaccinate bats could curb the spread of deadly diseases.

More than 1 in 7 people worldwide have had Lyme disease

Research published in 2022 suggests that 14.5% of the world's population has contracted Lyme disease. Researchers arrived at that estimate by analyzing the presence of Lyme disease antibodies (indicating prior infection) across 89 studies conducted between January 1984 and December 2021. The works collectively included blood samples from more than 150,000 people. (Some user may encounter a paywall.)

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.)

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...

Mapping the spread of a dangerous fungus growing in US healthcare facilities

Explore the data showing how the fungus C. auris has spread in the US, with more than 10,000 reported cases since 2016. Recommended steps to prevent infections and limit their spread have been successful in some areas, but infection control remains complicated because the fungus is often now multidrug-resistant.

See the polio cases that occur worldwide each year by region

Worldwide, the number of cases of polio reported each year from 1980 to 2024 has declined. This graphic depicts regional trends and declines by year.

See how each of the more than 2 million known species relates to each other—and to common ancestors—in this zoomable tree of life.

Powassan virus, a rare tick-borne disease named after the Canadian town where it was discovered in 1958, is on the rise in the northeastern United States, and it kills roughly 10% to 15% of patients with symptomatic disease.

Neglected tropical diseases affect more people than the population of Europe

This group of conditions, which includes hookworm, sickens roughly one in seven people on the planet—a tally which dwarfs Europe's population of roughly 450 million. International cooperation and donations are helping to control some of these illnesses, which can be caused by parasites, viruses, and bacteria. They're all treatable or preventable, but primarily occur among poor, isolated communities that may not receive adequate care.

Horses account for about 96% of known mammalian cases of West Nile virus infection beyond humans.

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.

Explore this hantavirus cruise ship outbreak case map from May 2026

Assembled from case information from state and health agencies, this detailed mapping includes the last known locations of each confirmed, deceased, and suspected case and their status.

Bird Flu is spreading—what does that mean for us and other species?

The rapid global spread of H5N1 bird flu—from remote Antarctic islands to US farms—shows how animal spillover, driven by human activity and ecological disruption, is accelerating pandemic risk across species long before sustained human transmission begins.

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.)

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.

Before vaccines, there was 'variolation': what was it?

Before the technology behind vaccinations was discovered, some keen observers of medicine around the globe noticed how previous infections could impact future ones. Learn about the techniques early physicians used before they had vaccines.

Our World in Data's COVID-19 tracker, with global case, death, and vaccination data for every country, though updates to the dataset ended in 2024.

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.

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.

Visualizing the world's food supply chains

The world's food supply chain is complex and lopsided, with much of the world's nutrient-rich food ending up in Europe and North America. This visualization illustrates the paths our food takes around the world, from starchy vegetables in...

Invasive species can harm infrastructure and threaten human health

The wildfires in Hawaii in 2022 were made worse by flammable invasive grasses introduced from Africa as livestock pasture, and Zebra mussels native to the Caspian and Black Seas have spread across Europe and the US, where they can clog power plant pipes. Invasive mosquitoes can carry diseases, such as dengue and malaria.

'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.

Hear from a NYC public health official who led the first US investigation into West Nile about the challenges investigators faced and their working theories about that outbreak.