Climate Change + Lyme Disease: Why Rates Are Rising with Temps

What do shifts in climates have to do with tick-borne illnesses?

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Despite increasing awareness of Lyme disease—and improved education for how to prevent and treat tick bites—Lyme disease rates seem to be on the rise. In 1997, just under 13,000 cases of Lyme disease were reported; by 2017, about 29,500 confirmed cases were reported, plus an additional 13,000 probable cases that went unreported, according to the Centers for Disease Control and Prevention (CDC).  

So what gives? Well, experts actually have a pretty good idea of what’s fueling the increase: rising temperatures from the climate crisis. 

Lyme disease is a vector-borne illness, meaning it’s carried and spread by a vector—an organism that can transmit infections. In this case, ticks are the guilty vector. By biting humans for food, ticks may spread the bacterium Borrelia burgdorferi, which causes Lyme disease.

Not every tick carries the bacterium that causes Lyme disease, but if you’re infected, you might notice symptoms like fever, headache, fatigue, and a bullseye-shaped rash. While that unique rash is commonly associated with Lyme disease, it's important to note that not everyone with Lyme disease will develop the rash. Learn more about symptoms of Lyme disease here.

For most people, Lyme disease is an infection that passes with antibiotics after a few weeks, according to the CDC. However, without treatment, Lyme disease can spread to organs in the body and cause serious complications. (Additionally, some people experience an autoimmune response to the infection and develop what many call “chronic Lyme disease,” but doctors call post-treatment Lyme disease syndrome.)

The Effect of Climate Change on Ticks and Lyme Disease

To put it simply, changes in climate and shifts in seasons throughout the United States are in turn changing the tick population. Ticks are populating different areas for different time periods, thus living in areas that are not used to dealing with ticks.

Think of it this way: Since Lyme disease records started being tracked, almost all cases happened in the same two regions in North America. That included the northeast—Pennsylvania, New Jersey, Connecticut, Rhode Island, Maryland,  New York, Vermont, New Hampshire, and Maine—and the Great Lakes region, specifically Minnesota and Wisconsin.

Since Lyme disease is prevalent in these areas, most people living there are used to dealing with ticks and know the good tricks to keep ticks off of them, such as:

  • Wearing long sleeves, long pants, and long socks

  • Using insect repellents when outdoors

  • Avoiding areas with high grass

  • Checking clothing and skin for ticks after coming inside, especially in hidden spots like the back of the knees or under the arms.

  • And showering soon after being outdoors.

However, when ticks venture into new regions, they prey on humans who aren’t as versed in these guidelines. Changes in temperature and rainfall associated with the climate crisis has led ticks to roam to new places, making more and more people vulnerable to the risks. The typical "tick season" may also last longer than people are used to. Currently, the vast majority of Lyme disease cases occur in June and July, according to the CDC, but this may start to spread more into May and August.

Experts expect the rates of Lyme disease to continue increasing—as well as other vector-borne illnesses that haven’t typically been a threat in the United States, such as malaria. It’s recommended to arm yourself with tips for tick prevention, even if you’ve never needed ‘em before.

Here are other ways the climate crisis could affect your health