It’s tiny, black with white spots, has a needle-like probe, and it’s now one of the most dangerous killers in the world.

While there are many species of mosquitoes around the world, aedes aegypti is special. It prefers the blood of humans almost exclusively, it lays eggs just about anywhere, and it can pass on some of the most vile diseases known to man — including the recent oubreak of the previously unknown to popular culture Zika virus, according to a Washington Post report.

Aedes aegypti can spread some pretty awful stuff, like dengue fever, yellow fever, zika, and chikungunya, to name a few.

Peter Hotez, who is the dean of the National School of Tropical Medicine at Baylor College of Medicine, said according to the report that aedes aegypt is “one of the most efficient killers in the world.”

The species has been wreaking havoc for quite a while. Aedes aegypti was behind the yellow fever outbreak of the 1890s, which got so bad that the French had to halt work on the Panama Canal, and also caused soldiers in the Spanish-American War to fall ill. Today, 20 million people get sick with dengue fever, all caused by aedes aegypti.

A number of factors converge to make aedes aegypti such an efficient killer. For one thing, it is found in regions of the world where more than half the human population of the Earth lives. It thrives in urban environments where trash abounds, and doesn’t even need water to survive. The eggs can survive for a year or more, waiting for the water to come to it before hatching. Females lay eggs after each feeding, leaving them everywhere, and they can often be found in artificial containers left lying around.

But it’s also the way the mosquito carries the diseases. In most, the disease simply sits inside the mosquito and doesn’t make its way out. But in aedes aegypti, the virus replicates and finds its way to the salivary glands, so when the mosquito bites a person, the virus makes its way into the human body.