Tick Season Is Peaking: What NPs Need to Know About Lyme, Alpha-Gal, Babesiosis, and Powassan Virus

 

Tick Season Is Peaking: What NPs Need to Know About Lyme, Alpha-Gal, Babesiosis, and Powassan Virus

ED visits for tick bites are at their highest rate since 2017. Here's how to recognize, diagnose, and counsel patients on the diseases behind them.

Source: Stern O. Summer marks peak season for tick-borne diseases: how to educate patients. Published August 10, 2026, citing CDC data and Rodino KG, Theel ES, Pritt BS, J Clin Microbiol. 2025.

Mosquitoes usually get top billing in summer patient-education conversations, but ticks deserve equal attention this year. Emergency department visits for tick bites are at their highest rate since 2017, and the CDC estimates roughly 31 million tick bites occur annually across the US. Tick-borne disease cases overall have more than doubled since 2004 — and that figure is likely an undercount, since many of these illnesses present with vague, overlapping symptoms and patients often don't recall being bitten.

The black-legged (deer) tick now inhabits roughly 45% of continental US counties, a substantial range expansion since the early 1900s, according to Bobbi S. Pritt, MD, chair of the division of clinical microbiology at Mayo Clinic. Warming climates, expanding deer and rodent populations, and increased land use are all expected to keep pushing tick ranges — and the diseases they carry — into new territory. Peak season runs April through October, which makes now the right time to sharpen recognition of the major tick-borne illnesses.

Disease Overview

Disease	Primary Vector	Region of Concentration	Hallmark Feature
Lyme disease	Ixodes (black-legged/deer tick)	Northeast/Mid-Atlantic, WI, MN, MI (~96% of cases)	Erythema migrans rash in ~70% of cases; 3-stage progression
Alpha-gal syndrome	Lone-star tick	South, East, Central US	Delayed allergic reaction to red meat/mammalian products
Babesiosis	Ixodes (black-legged/deer tick)	Overlaps with Lyme-endemic areas	Can also spread via transfusion, transplant, or perinatally; frequent Lyme co-infection
Powassan virus	Ixodes (black-legged/deer tick)	Northeast, Upper Midwest	Only tick-borne encephalitis in the US; can transmit in as little as 15 minutes

 

Lyme Disease

Lyme remains the most common tick-borne illness in the US. Reported cases (34,945 in 2019) likely understate true incidence by 8- to 12-fold. Disease typically unfolds in three stages: an early localized stage marked by erythema migrans (present in roughly 70% of cases, expanding in about 75% of those, not always in a classic bullseye pattern); early disseminated infection days to weeks later, which can bring secondary rashes, neurologic symptoms (~10%), or Lyme carditis (~4%); and late/persistent infection, averaging 6 months after rash onset, with recurrent arthritis — usually in the knee — in roughly 60% of patients. About 10% of patients go on to develop post-treatment Lyme disease syndrome (fatigue, myalgia, cognitive impairment).

Treatment is a course of doxycycline, amoxicillin, or cefuroxime axetil, ideally started within 72 hours of removing a high-risk tick. “High-risk” means an identified Ixodes species, attachment of more than 36 hours, and a bite in a highly endemic area; bites that don't meet all three criteria warrant watchful waiting rather than empiric treatment.

Alpha-Gal Syndrome

Lone-star tick bites can transmit the alpha-gal molecule into the bloodstream, triggering a potentially life-threatening delayed allergy to red meat and other mammalian products. The CDC estimates nearly 450,000 people may be affected, with more than 110,000 cases identified over the past 25 years; the first reported death linked to alpha-gal syndrome occurred in New Jersey last year. Range expansion is expected to continue northward and westward with ongoing climate change. Adult female lone-star ticks are identifiable by a distinctive white dot on the back; South, East, and Central states currently carry the highest exposure risk.

Babesiosis

Babesiosis is notable for its non-tick transmission routes — blood transfusion, organ transplant, and perinatal transmission are all possible in addition to tick bites. It's the third most common Ixodes-transmitted disease (2,418 cases reported in 2019). Presentation ranges from asymptomatic (about half of children, one-quarter of adults) to severe, with fever, malaise, joint pain, GI symptoms, hemolytic anemia, thrombocytopenia, or organ dysfunction in serious cases. Hospitalized patients face 6–9% fatality, rising to 21% among immunosuppressed patients. Concurrent Lyme disease occurs in an estimated 6–23% of babesiosis cases and increases severity — worth screening for when either diagnosis is suspected. First-line treatment is azithromycin plus atovaquone, with clindamycin plus quinine as an alternative; immunocompromised or asplenic patients may need higher, prolonged dosing.

Powassan Virus

Rarer than the other three, but rising: cases stayed under 20 annually from 2004 to 2015, then climbed to 60 cases (9 deaths) and 76 cases (10 deaths) in the two most recent years reported, with 29 cases already logged across 9 states this year — 27 of them neuroinvasive. Powassan is the only tick-borne encephalitis found in the US, with a fatality rate near 10% and lasting neurologic effects in roughly half of survivors. Transmission can begin in as little as 15 minutes of attachment, with infection onset possible within 6 hours — far faster than the 24–48-hour window typical of most other tick-borne diseases. Diagnosis requires a two-pronged approach: molecular testing 5–7 days after symptom onset, plus serology after the first week.

Diagnostic Considerations

Serology remains the default for most tick-borne diseases, but it has real limitations for anaplasmosis, ehrlichiosis, and babesiosis specifically: seroconversion can take 7–14 days, some patients never mount a detectable IgG response, antibodies can persist for months to years after resolved infection, and specificity issues can produce false positives or negatives. For those three diseases, nucleic acid amplification tests (NAATs) are preferred over serology despite the lack of an FDA-approved NAAT specific to this use — the tests are limited by a short viremic window but still outperform antibody testing in this context. Broader metagenomic testing is also emerging as an option when the clinical picture is nonspecific enough that casting a wide net for any bacterium, virus, or parasite is warranted.

 

■ CLINICAL BOTTOM LINE •     Reserve single-dose/short-course prophylactic doxycycline for confirmed high-risk exposures: Ixodes species, ≥ 36 hours attachment, highly endemic area, treated within 72 hours of removal. •     Don't rule out Lyme disease just because a rash is absent — roughly 30% of patients never develop erythema migrans. •     Ask about new-onset red meat reactions (hours after eating, not immediate) in patients from lone-star tick territory — alpha-gal syndrome is easy to miss without a specific index of suspicion. •     When babesiosis is confirmed, screen for concurrent Lyme disease, and vice versa — co-infection is common and changes the clinical picture. •     For anaplasmosis, ehrlichiosis, and babesiosis, favor NAAT testing over serology when available, given serology's seroconversion lag and specificity limits. •     Counsel on same-day tick checks, prompt mechanical removal with forceps, and EPA-registered repellents (DEET, picaridin, permethrin) as the highest-yield prevention strategies.

 

■ CASE FROM PRACTICE A 42-year-old returns from a camping trip in western Wisconsin 10 days ago with fatigue, joint aches, and a low-grade fever. He doesn't recall a tick bite or rash and initially attributes his symptoms to a summer cold. On exam, there's no visible erythema migrans, but he mentions his knee has felt “achy and swollen” for the past two days. This presentation is a reminder that absence of a rash doesn't rule out Lyme disease, and that joint symptoms can be an early clue even before the classic late-stage arthritis picture develops. Given the endemic location and symptom cluster, this warrants Lyme serology, consideration of co-testing for babesiosis given regional overlap, and a treatment conversation rather than waiting for a more “textbook” presentation to appear.

 

■ A NUANCE WORTH FLAGGING Rising case counts don't always mean rising true incidence. Powassan virus cases are climbing partly because of genuinely expanding tick ranges, but also because of limited diagnostic testing and low clinician awareness historically — better detection can look like an outbreak even when some of the increase reflects better ascertainment. The same caution applies to alpha-gal syndrome: a single reported death establishing causality doesn't quantify overall mortality risk, and the ~450,000-person prevalence estimate is exactly that, an estimate, built from a condition that is likely substantially underdiagnosed given its atypical delayed-allergy presentation. Treat these figures as directionally meaningful rather than precise.

 

📚 Board Prep: What to Know

Tick-borne disease questions often hinge on precise criteria and stage-based presentations. Key points to have cold:

•     Prophylactic doxycycline criteria: Ixodes species tick, ≥ 36 hours attachment, high-endemic area, given within 72 hours of removal — all four must be met.

•     Lyme diseases' three stages: early localized (erythema migrans), early disseminated (secondary rashes, neuro symptoms, carditis), and late/persistent (recurrent arthritis, usually knee).

•     Babesiosis transmission is not limited to tick bites — also via transfusion, transplant, and perinatal routes; know this as a distractor against “tick-only” transmission questions.

•     Powassan virus is the only tick-borne encephalitis native to the US, with transmission possible in as little as 15 minutes of attachment.

•     NAAT over serology for anaplasmosis, ehrlichiosis, and babesiosis, due to seroconversion delay and specificity limitations of antibody testing.

•     Alpha-gal syndrome is a delayed (not immediate) IgE-mediated allergic reaction to mammalian meat, transmitted via lone-star tick saliva — distinct mechanism from the Ixodes-transmitted diseases.

References

Centers for Disease Control and Prevention. CDC data show weekly ER visits for tick bites higher than usual. Published April 23, 2026.

Rodino KG, Theel ES, Pritt BS. Update on North American tick-borne diseases and how to diagnose them. J Clin Microbiol. 2025;63(8):e00807-23.

Eilbert W, Matella A. Tick-borne diseases. Emerg Med Clin N Am. 2024;42(2):287-302.

Centers for Disease Control and Prevention. Data and Maps for Powassan. Updated June 3, 2026.

Ho BM, Davis HE, Forrester JD, et al. Wilderness Medical Society clinical practice guidelines for the prevention and management of tick-borne illness in the United States. Wilderness Environ Med. 2021;32(3):474-494.

Varon AR, Prusinski MA, O'Connor C, et al. Epidemiology and risk analysis of Powassan virus infection, New York state, USA, 2013-2023. Epidemiol Infect. 2026;154:e21.

Centers for Disease Control and Prevention. About alpha-gal syndrome. Published January 5, 2026.

Stern O. Summer marks peak season for tick-borne diseases: how to educate patients. Published August 10, 2026.

This post is intended for clinical education purposes and does not replace individualized clinical judgment or current prescribing guidance.