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What’s the big deal? I can handle a few mosquito bites. Scientists believe that mosquitoes choose their human victims by the scent of the bacteria on our skin and in our sweat. Because our bacterial communities vary, some of us are more prone to bites than others. To anyone who has scratched herself silly after a camping trip, the importance of an effective repellent is obvious. But even if you’re lucky enough to be unappetizing to mosquitoes, there’s another reason to choose your bug defense carefully: Insect-borne illnesses are on the rise, and some can be serious, even deadly. Lyme disease, which is transmitted by deer ticks, causes debilitating symptoms in more than 20,000 people every year. In 2013, 2,374 people in 48 states contracted the mosquito-borne disease West Nile virus, and 114 of them died. As climate change intensifies, public health experts expect that more breeds of mosquito will thrive in the United States. As a result, they predict an uptick in West Nile and other insect-borne illnesses, such as yellow fever. Since 2001, Florida, Hawaii, and Texas have had outbreaks of dengue, another mosquito-borne disease that had been considered eliminated in the United States since 1945.