As the summer sun beckons Americans outdoors, a less welcome guest is making its presence felt across the country: ticks. Recent reports and scientific studies reveal that tick populations are not only thriving in their traditional strongholds but are also spreading into new areas, sometimes hitching rides from far-flung corners of the globe. The implications for public health are significant, with experts urging vigilance as new tick-borne diseases emerge and familiar threats like Lyme disease continue to loom large.
According to a 2024 report from Terminix, Missouri and Illinois are among the states facing some of the nation’s worst tick problems, thanks to their warm climates, high humidity, and abundant green spaces. The report, cited by local news outlets in St. Louis, ranks Illinois at 17th and Missouri at 22nd for tick prevalence nationwide. California tops the list, followed by Florida, Texas, Pennsylvania, and New York. Notably, Pennsylvania, New York, and New Jersey report the highest rates of Lyme disease cases, a finding echoed by the Centers for Disease Control and Prevention (CDC).
Urban dwellers aren’t immune, either. Terminix identifies New York City, Los Angeles, Philadelphia, San Francisco, and Washington D.C. as the five most tick-infested cities in the United States. The company’s advice for residents is straightforward: keep yards trimmed, wear long sleeves outdoors, use EPA-approved insect repellents, and check for ticks after returning inside. These simple steps, they say, can go a long way toward reducing the risk of tick-borne illness.
But it’s not just native ticks that are causing concern. In a study published in the journal iScience in 2025, researchers documented the arrival of seven exotic tick species in Connecticut between 2019 and 2023. These ticks, native to places as diverse as Germany, Guatemala, Costa Rica, Poland, Scotland, Tanzania, and Belize, were brought to the U.S. by international travelers. The study highlights how globalization and increased travel are inadvertently introducing new species—and potentially new pathogens—into the American ecosystem.
“The findings highlight the risk of invasive ticks and their pathogens spreading to new areas of the US,” the study’s authors wrote. They emphasized the importance of surveillance programs focused on tick species identification and pathogen screening to protect both human and veterinary health. The arrival of these non-native ticks is not an isolated incident; over the past 50 years, more than 140 nonnative tick species have entered the U.S., with some, like the longhorned tick (Haemaphysalis longicornis), now established across multiple states.
What does this mean for the average American? More ticks, more often, and with greater risk. The CDC estimates that approximately 476,000 people in the U.S. may be diagnosed and treated for Lyme disease each year. This illness, caused by the bacterium Borrelia burgdorferi and transmitted primarily by deer ticks (also known as blacklegged ticks), can range from a rash and flu-like symptoms to severe neurological problems if left untreated. The disease is most common in the Northeast, Upper Midwest, and mid-Atlantic regions, but as ticks spread, so does the risk.
Other tick-borne diseases are also on the rise. The lone star tick, for example, can trigger Alpha-gal syndrome (AGS), an allergy to red meat. While most cases result in symptoms like vomiting and diarrhea, some can escalate to life-threatening anaphylactic shock. The rapid spread of both native and exotic ticks increases the chances that Americans will encounter these and other emerging health threats.
In Arizona, Lyme disease remains rare, with only 16 documented infections across eight counties in 2023. According to Magda Rodriguez, spokesperson for the Arizona Department of Health Services, there have been no confirmed cases contracted from tick bites within the state. The tick species that transmit Lyme disease prefer higher humidity and are not commonly found in Arizona, though the “western tick vector” has been identified in Mohave County’s Hualapai Mountains—without evidence of carrying pathogens. Still, many Arizonans contract Lyme disease while traveling to areas where the disease is endemic, highlighting the importance of awareness and prevention even in states perceived as low-risk.
Linda Giampa, executive director of the Bay Area Lyme Foundation, offered practical advice: “We recommend wearing white so the ticks are more visible, tick-checking yourself and your gear when you arrive home, and being vigilant to see a doctor if you have any symptoms.” Removing attached ticks promptly with tweezers and monitoring for signs of illness can help reduce the risk of serious complications.
Scientists are working hard to keep pace with these shifting threats. As noted by Science X Network, certain tick species are spreading to areas of the U.S. where they had not been found before, carrying new health risks. Researchers are conducting surveys to track tick distribution, but health officials often struggle to keep up with the rapid changes. Accurate identification of ticks is a crucial step in assessing the risk of acquiring a specific tick-borne disease, and DNA analysis is increasingly used to confirm species and screen for pathogens.
The recent study in Connecticut found that two Amblyomma mixtum nymphs—one from Guatemala and one from Costa Rica—tested positive for Rickettsia amblyommatis, a bacteria related to those causing Rocky Mountain spotted fever. While the medical significance of R. amblyommatis remains uncertain, the discovery underscores the need for ongoing vigilance. The researchers stress the importance of providing clinicians and public health officials with up-to-date information about various tick species, including how to distinguish between native and non-native types.
Public awareness is key. Officials recommend that travelers avoid tick exposure by staying alert to their surroundings, wearing appropriate clothing, and checking for possible bites after returning indoors. Surveillance and education, they argue, are essential tools in the fight against tick-borne diseases. As one researcher put it, “Setting up surveillance programs that include tick species identification and pathogen screening can help protect human and veterinary health.”
With tick season in full swing and new species arriving at America’s doorstep, staying informed and taking simple precautions can make all the difference. Whether you’re hiking in the woods of Missouri, exploring the green spaces of Illinois, or returning from a trip abroad, a little vigilance goes a long way in keeping ticks—and the diseases they carry—at bay.
