A closeup of a mosquito.

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.

In fact, a recent analysis by the Centers for Disease Control and Prevention found that since 2004, nine tick or mosquito diseases—including the Zika virus—have been reported for the first time in the U.S. and its territories.

The reasons for this upward trend are not surprising. Rising global temperatures, increasing suburbanization, and unprecedented international travel have forced bugs and humans into ever-closer proximity and given each new illness 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.

In recent years, Zika has gotten a lot of attention. In the continental U.S., West Nile virus remains the most commonly transmitted mosquito-borne disease by far, significantly outpacing Zika. For 2017 the CDC reported more than 2,000 cases of West Nile in 47 states and the District of Columbia. But only 7 people contracted Zika after being bitten by mosquitoes in Florida and Texas last year (though more than 400 people got sick with Zika while traveling to affected areas outside the U.S., and 665 people were infected in the U.S. territories, including Puerto Rico). 

More on Mosquitoes and Ticks

And Lyme disease, which is spread by ticks, is still more common than any mosquito-borne pathogen. The CDC estimates that about 300,000 Americans developed Lyme last year. And though the disease itself is still concentrated in the Northeast, the range of the deer tick that can carry it 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 updated our interactive map with the most recent data from 2017 for concentrations of mosquito-borne diseases and 2016 for tick-borne diseases. 

Guide to Mosquito and Tick Diseases

Where Most Cases Occur

Serious Side Effects

Symptoms appear


Common Symptoms

The Lowdown on Insect Repellents

Bug bites are not only annoying, they can also transmit diseases. On the 'Consumer 101' TV show, host Jack Rico goes inside Consumer Reports' labs to find out how CR tests insect repellents to make sure you are getting the most protection.