Energy & Climate

Climate change driving surge in tick-borne diseases across US Northeast region

The Checkup with Doctor Mike · I Was Wrong About My Patient's 103° Fever · July 15, 2026

The Checkup with Doctor Mike

I Was Wrong About My Patient's 103° Fever

"Tick-spread illnesses are on the rise in the US. Why? Summers are hotter, are longer, springs are earlier, winters are milder, so there's less tick die-off. So ticks are more present and are spreading more readily. Part of this is due to climate change because of this weather cycle that we're experiencing."

A practicing physician in the Northeast reports that tick-borne illnesses like anaplasmosis are increasing due to climate change creating longer warm seasons and milder winters that reduce tick die-off rates. The doctor's recent diagnostic case illustrated how these diseases are becoming more common and harder to diagnose, with anaplasmosis presenting alongside other infections. The warning comes as tick populations expand and disease vectors multiply.

About this episode

A physician recounts a complex diagnostic case involving a 45-year-old high school gym teacher who presented with persistent high fevers reaching 103.5 degrees Fahrenheit but no other symptoms. The patient initially tested positive for mononucleosis reactivation, appeared to recover completely after five days, but then experienced fever recurrence another five days later. After extensive testing ruled out respiratory, gastrointestinal, urinary, and neurological causes, the doctor consulted with emergency medicine colleagues and ultimately diagnosed the patient with anaplasmosis, a tick-borne bacterial infection spread by the same ticks that carry Lyme disease. The case highlights the challenges of diagnosing fever of unknown origin and the growing prevalence of tick-borne diseases in the Northeast United States. The doctor attributes the rise in such illnesses to climate change, explaining that hotter, longer summers and milder winters reduce tick die-off rates, allowing tick populations to expand. Treatment with doxycycline for two weeks resolved the infection completely, with all laboratory markers returning to normal. The physician emphasizes the importance of considering tick-borne illnesses in endemic areas, noting that delayed diagnosis could cause serious harm to patients. The case is considered unusual enough that the medical team is preparing a formal case write-up for publication.

Key takeaways

A 45-year-old patient with persistent high fevers up to 103.5°F initially tested positive for mononucleosis reactivation but was ultimately diagnosed with anaplasmosis.
The patient experienced complete fever resolution after five days, followed by unexpected recurrence five days later, complicating the diagnosis significantly.
Anaplasmosis is a bacterial infection spread by the same deer ticks that transmit Lyme disease but requires different diagnostic testing.
The physician reports tick-borne illnesses are increasing across the US Northeast due to climate change extending warm seasons and reducing winter tick die-off.
Treatment with doxycycline antibiotics for two weeks completely resolved the infection with all laboratory markers returning to normal ranges.
Emergency medicine doctors consulted on the case recommended empiric doxycycline treatment before the final diagnosis was confirmed through specialized tick-borne panel testing.
The medical team is preparing a formal case write-up due to the unusual presentation of concurrent mononucleosis reactivation and anaplasmosis infection.