The animal kingdom is full of deadly weapons. A lion’s teeth can pierce through flesh with frenzied force, rattlesnakes can inject toxins into the bloodstream, and hippos can kill you with their powerful jaws. These are just a few of the deadly creatures. But which animal kills the most people?

According to the Centers for Disease Control and Prevention, the “world’s deadliest animal” is the mosquito, which, by some estimates, kills between 500,000 and more than a million people a year. After all, mosquitoes are carriers of diseases, especially malaria.

“Malaria has been too persistent in destroying humanity for too long,” said Shannon Lado, a disease ecologist at the Carey Ecosystem Research Institute in Millbrook, New York.

Malaria is caused by parasitic single-celled organisms of the genus Plasmodium, which are transmitted from person to person by Anopheles mosquitoes. The disease is rare in North America and Europe, but is common in parts of Africa, Southern Asia and South America, according to Our World in Data. According to the World Health Organization, malaria caused about 619,000 deaths worldwide in 2021.

The disease is usually treatable with available medical care. But for people at high risk, such as young children, pregnant women, and people with immunodeficiency such as HIV/AIDS, malaria can be very serious. According to the World Health Organization, about 80% of all malaria deaths in Africa occur in children under the age of 5.

Mosquitoes also spread a number of other diseases such as dengue fever, chikungunya, West Nile virus, Zika virus, and the parasitic infection lymphatic filariasis.

So why are mosquitoes so effective at spreading disease? First, female mosquitoes feed on blood, which means they can very easily transfer pathogens from one person’s blood to another, Ladeo said. They are also small and winged, meaning they can spread easily and bite people unnoticed. There is also the fact that we share a common ecosystem and resources. Mosquitoes need water to reproduce, just as humans rely on water to live, which means we live in the same places.

“We can’t completely detach ourselves from the habitat they need,” Lado said.

However, there are ways to reduce the risk of mosquito-borne illness. Lado noted that even small infrastructure upgrades can make a big difference. For example, window screens can help keep mosquitoes out of your home, and plumbing fixtures can prevent water from entering outdoor pools.

These possibilities, he says, are part of why malaria is not prevalent in many parts of the world with better infrastructure. And where such facilities are not available, mosquito nets can help keep bugs out of people’s beds.

These preservatives may also protect against other mosquito-borne diseases, such as dengue, which kills tens of thousands of people each year. But public health efforts against mosquito-borne diseases are facing an uphill battle against climate change. As the planet warms, if local environments become more hospitable to these pathogens and the mosquitoes that carry them, these diseases could begin to spread to new areas. Andy Macdonald, an ecologist at the University of California at Santa Barbara, talked about this.

However, mosquitoes are not the only deadly animals on our planet. According to the World Health Organization, snakes kill between 81,000 and 138,000 people each year, making them one of the deadliest animals to humans. And according to the WHO, rabies, a disease transmitted by the bite of an infected mammal (usually a dog), kills about 59,000 people each year.

Other animals, such as freshwater snails and killer insects, also transmit potentially deadly diseases to humans, such as schistosomiasis and Chagas disease, which each kill thousands of people each year, according to the data. But only one animal competes with the mosquito for the title of deadliest for humans. Murder and gunfights killed about 553,000 people in 2017, making humans one of the deadliest creatures on earth, according to UN estimates.