When people think of dangerous animals in Alaska, bears usually come to mind. When a bear hurts somebody, it's big news, but it's actually pretty rare. The deadliest animal in the world is common in Alaska, but it's not deadly here in the north. It's the mosquito.
Alaska is famous for mosquitoes, and most Alaskans have experienced a relentless, maddening horde of mosquitoes on a summertime fishing or camping trip. But in tropical countries where mosquitoes carry diseases like malaria, dengue fever, and yellow fever, mosquitoes are deadly. There were almost 200 million cases of malaria in 2013, and between a half-million and a million deaths. In one sense, it's not the mosquito that kills, but a protozoan parasite the mosquitoes carry that causes malaria. But mosquitoes' role in delivering the disease-causing protozoan to people makes it a killer.
Why don't Alaska mosquitoes carry malaria? The main limiting factor for the transmission of malaria is temperature. It has to be warm enough for that protozoan parasite to complete its life cycle. At 77 degrees, the parasite can complete its life cycle in a little less than a month. At temperatures below 68 degrees, the parasite can't complete its life cycle within the life span of the adult mosquito.
While Alaska is not at risk for malaria, it's not strictly a tropical disease. A malaria epidemic killed thousands of people in Oregon in the 1830s.