Mosquitoes and ticks are spreading more rapidly than ever, both across the U.S. and around the globe. And with each new season, the list of diseases they carry grows longer.

The reasons for this upward trend are not surprising: Rising global temperatures, increasing urbanization, and unprecedented international travel have forced bugs and humans into an ever-closer proximity, and given each new scourge the potential to go global, quickly.

But it can be tough to know exactly which mosquito- and tick-borne diseases to worry about in any given place, at any given time.

More on Mosquitoes and Ticks

In recent years, diseases such as Zika and Powassan have gotten the most attention.

But in the continental U.S., West Nile virus remains the most common mosquito-borne disease by far, outpacing Zika by an order of magnitude: In 2016, the Centers for Disease Control and Prevention reported more than 2,000 cases of West Nile in 46 states, compared with only 200 cases of Zika in just Florida and Texas (an additional 80 or so cases of Zika were spread through sexual or mother-to-fetus transmission).

And Lyme disease, which is spread by ticks, is still more common than any mosquito-borne pathogen. The CDC estimates that 300,000 Americans developed Lyme last year. And though the disease itself is still concentrated in the Northeast, the range of its vector (the deer tick) has spread by more than 300 percent in the past three decades.

There are proven ways to protect yourself (and your family) from all these diseases: Keeping your grass cut low, ridding your yard of standing water, tucking your pants into your socks on long walks, and wearing an effective insect repellent on your exposed skin are all good places to start.

But it also helps to know which diseases are spreading where, and which signs and symptoms to watch out for in your particular neck of the woods. To help you keep track, we’ve created this interactive map.   

Guide to Mosquito and Tick Diseases

Where Most Cases Occur

Serious Side Effects

Symptoms appear


Common Symptoms