Which animal kills the most people every year?

The animal kingdom is full of deadly weapons. A lion's teeth can rip apart flesh with ferocious intensity, rattlesnakes can inject toxins into the bloodstream and hippos can kill you with their powerful jaws.

These are just a few examples of deadly creatures. But which animal kills the most humans?

According to the Centers for Disease Control and Prevention (CDC), the "world's deadliest animal" is the mosquito, which by some estimates, kills 500,000 to more than a million people per year. 

The main reason mosquitoes are so deadly? They are a vector for disease, particularly malaria.

"Malaria has been so persistently devastating to human populations for a long time," Shannon LaDeau, a disease ecologist at the Cary Institute of Ecosystem Studies in Millbrook, New York, told Live Science.

Related: Why do mosquitoes buzz in our ears?

Malaria is caused by parasitic single-celled organisms in the Plasmodium genus, carried from person to person by Anopheles mosquitoes. While the disease is rare in North America and Europe, it's common in parts of Africa, southern Asia and South America, according to Our World in Data. Worldwide, malaria caused around 619,000 deaths in 2021, according to the World Health Organization (WHO).

The disease is often treatable with accessible health care. But for high-risk people — such as small children, pregnant people and people with immune deficiencies, like HIV/AIDS — malaria can be very serious. According to the WHO, about 80% of all malaria deaths in Africa were in children under age 5.

Mosquitoes also spread an array of other diseases, including dengue, chikungunya, West Nile virus, Zika virus and the parasitic infection lymphatic filariasis. 

So why are mosquitoes so effective at spreading disease? For one, female mosquitoes feed on blood, which means they very easily transfer pathogens from one person's bloodstream to another, LaDeau noted. They're also small and winged, which means they can spread easily and bite people without being noticed. 

Then, there's the fact that we share an ecosystem and resources. Mosquitoes rely on water to reproduce, just as humans rely on water to live, which means we tend to live in the same places.

"We can't fully separate ourselves from the habitat that they need," LaDeau said.

Still, there are ways to reduce the risk of mosquito-borne illnesses. Even small infrastructure updates can make a big difference, LaDeau noted. For example, window screens can help keep mosquitoes outside homes, and plumbing can keep water sealed away so it's not in open pools.

Those amenities are part of why malaria isn't widespread in many parts of the world with better infrastructure, she said. And in areas without these accommodations, mosquito nets can help to keep the insects away from people's beds.

These preventions can also protect against other mosquito-borne illnesses, like dengue, which kills tens of thousands of people each year. But public health efforts against mosquito-borne illnesses are facing an uphill battle under climate change. As the planet warms, these diseases could start to spread into new areas if local environments start to become more hospitable to these pathogens and the mosquitoes that carry them, Andy MacDonald, a disease ecologist at the University of California, Santa Barbara, told Live Science.

Mosquitos, however, aren’t the only supremely deadly animals on our planet. Snakes kill between 81,000 and 138,000 people every year, according to the WHO, making them one of the most deadly animals to humans. And rabies, a disease spread by a bite with an infected mammal (often a dog), kills about 59,000 people each year, the WHO reported.

Other animals, such as freshwater snails and assassin bugs, also spread potentially deadly diseases to humans like schistosomiasis and Chagas disease, which each kill thousands of people every year, according to the WHO.

But only one animal rivals the mosquito for the title of most deadly to humans. A report from the United Nations estimated that homicide and armed conflict killed about 553,000 people in 2017 — making humans one of the deadliest creatures on Earth.