Researchers at Cary Institute of Ecosystem Studies in Millbrook have discovered a disturbing trend: Tick-borne diseases are increasing in the northeastern United States, with many ticks capable of transmitting more than one serious disease.
The institute’s Ecosphere study in December revealed that among thousands of deer (blacklegged) ticks collected from its Dutchess County campus, nearly 40% carried at least one pathogen. Notably, 11% of the ticks tested positive for at least two — most commonly the bacteria causing Lyme disease and the parasite causing babesiosis (a life-threatening malaria-like illness). Researchers also found that the babesiosis parasite, once rare in the U.S., had more than doubled in prevalence, edging out Lyme as the most common pathogen (21% to 19%).
Tick-borne co-infections often lead to more serious, longer-lasting symptoms, and can overwhelm the immune system, making the diseases harder to treat.
New York consistently leads the nation in total tick-borne illnesses, with Dutchess County reporting some of the highest infection rates in the state. Lyme disease cases in the state have quadrupled since 2020, now exceeding 18,700 annually, accounting for 20% of all U.S. infections.
The incidence of babesiosis in New York has more than tripled since 2011. Total numbers are low in comparison to Lyme, with 670 cases annually (3,600 cases nationwide). But experts believe the true figures are vastly underestimated due to widespread misdiagnosis and underreporting: One study suggesting that numbers are as much as 40 times higher than recorded.
Babesiosis is flu-like, usually presenting with headache, muscle pain, and fever; unlike Lyme, there is no hallmark bull’s-eye rash. Symptoms can appear one to nine weeks after a bite. The causal parasites thrive in red blood cells — like malarial diseases — until the corpuscles burst. The resulting hemolytic anemia causes severe shortness of breath and jaundice; if not treated promptly, the disease can lead to respiratory and liver failure, and death.
The state’s Department of Health’s 2025 tick surveillance shows a surge in other potentially fatal tick-borne diseases, including Powassan virus, anaplasmosis, and ehrlichiosis, the last often carried by lone star ticks. These arthropods are also the prime transmitter of alpha-gal, a sugar molecule that can trigger a life-threatening allergic reaction to red meat in more than 40% of victims. An estimated 450,000 Americans have been sickened by alpha-gal syndrome since 2010, with one recorded death.
Scientists warn that climate change is fueling the tick population explosion and the rising incidence of tick-borne illnesses. Hotter springs and milder winters have allowed the arthropods to emerge earlier, linger longer, and expand their range. New York’s tick season began this year in late March, a full month earlier than in previous decades; it is expected to stretch well into November. Even with heavy winter precipitation, a thick snow layer acts as a kind of insulation that often protects ticks instead of killing them.
Housing developments have led to a surge in rodent and deer populations by displacing natural predators. These animals serve as asymptomatic carriers of ticks, allowing them to spread illnesses to humans. Residential development near wooded areas means that more people are living in high-risk tick zones.
Consult your health care provider immediately if a deer or lone star tick has been attached for more than 36 hours, is engorged, or if a rash or fever develops. Lyme disease is completely curable if treated early with a 10- to 14-day course of antibiotics. Your clinician may offer you one preventive dose of the antibiotic doxycycline, but only if the deer tick has been feeding less than 72 hours.
Babesiosis, anaplasmosis, and ehrlichiosis usually require up to three weeks of antibiotics (with the addition of an anti-malarial drug to eradicate babesiosis). The prophylactic treatment that successfully prevents Lyme disease is ineffective.
Not all tick bites require immediate medical attention: Dog ticks should be safely removed, and the bite site self-monitored for 30 days. A healthcare provider should be consulted promptly if any rashes or flu-like symptoms develop.
Stay healthy by avoiding ticks: Wear long pants tucked into your socks, and consider applying a tick repellent like permethrin to your clothing, especially to shoes and socks. When hiking, stay on the trail. Do a thorough tick check when you get home: Focus on your thighs, groin area, and the back of your head. Showering within two hours after an excursion lowers your risk of bite. If applicable, check your dog for ticks, too.
A Lyme disease vaccination is on the horizon for the first time in over two decades. Pfizer announced in March that it is seeking FDA approval after its vaccine showed over 70% efficacy in late-stage trials; Moderna is simultaneously advancing an mRNA-based immunization.
Dr. Mary Jenkins, a contributor to the Herald and member of its board of directors, retired after nearly 40 years as a family practice physician in New York state.