The Centers for Disease Control and Prevention estimates that between 2004 and 2019, the total number of tick-borne diseases in the United States more than doubled. In the meantime, other devastating pests that were previously constrained by cooler temperatures — like the dengue virus-carrying tiger mosquito, or the cabbage-munching harlequin bug — have also marched forth beyond their historic ranges.
“We’re venturing into uncharted waters in so many dimensions with climate change,” Dr. Raupp said.
By nature, ticks are travelers; they attach themselves to hosts in order to suck their blood, hitching a ride in the process. Scientists say an explosion in the population of the white-tailed deer, their primary host, has also helped them to spread.