Have you noticed more ticks in recent years? If so, you are not alone. Ticks, like the deer tick or blacklegged tick (Ixodes scapularis), are becoming more common in parts of the Northeast and Midwest. And with the ticks comes the potential for Lyme disease, the most common vector-borne disease in the United States.
The map above shows the distribution of Lyme disease cases between 2000 and 2019. The reported cases increase in both amount and geographic range in the past two decades.
Lyme disease is caused by a bacterium called Borrelia burgdorferi. The bacterium can enter humans if bitten by infected ticks. Because we can’t map the location of individual ticks, reports of Lyme disease are a useful proxy: where there is Lyme disease, there are ticks.
The spread of ticks and Lyme disease is not random. It follows a similar trend in warming temperatures. Deer ticks live in forests, lawns, and moist shrubby areas where they cling to thick vegetation and grasses. They are most active in spring, summer, and fall—a time of year that is becoming longer and warmer in many parts of the U.S.
Warmer temperatures mean longer portions of each year are more suitable for ticks. People also tend to spend more time outdoors when it’s warmer. These factors contribute to an ever-increasing window of opportunity for tick-human encounters.
Even still, people can enjoy being outdoors in tick habitat with a few safety measures. There’s no need to fear ticks, but it’s good to be aware of their increasing numbers.
By The Numbers
People diagnosed and treated for Lyme disease in the U.S. annually
New cases of Lyme disease officially reported to the CDC each year