Bimodal age distribution — children 5–15 years at elevated risk
Higher outdoor activity exposure in this age group
Pediatric alarm features
Facial nerve palsy — CN VII most common neurologic manifestation
Lyme arthritis — more common in children than adults with disseminated disease
Lyme carditis — rare in pediatric patients but reported
Serologic testing in children
Same two-tier approach as adults
Clinical diagnosis applies for classic EM — no testing required
School and activity return
No restriction required once tolerating antibiotics and afebrile
Educate family on tick prevention for future exposures
Background
Epidemiology
Incidence and geographic distribution
Most common vector-borne disease in the United States
~476,000 estimated new cases per year (CDC surveillance and modeling)
14 states account for 95% of reported US cases
Northeastern states: Maine, Vermont, New Hampshire, Connecticut, Rhode Island, Massachusetts, New York, New Jersey, Pennsylvania, Delaware, Maryland, Virginia
Midwestern states: Wisconsin, Minnesota
Expanding geographic range — climate warming extending Ixodes scapularis habitat
Seasonal distribution
Peak incidence May through August
Corresponds to nymphal Ixodes scapularis activity — primary transmission stage
Adult tick activity — fall and winter; lower transmission rate
Age distribution
Bimodal: children aged 5–15 years and adults aged 45–65 years
Both groups have higher outdoor recreational exposure
Tick vector biology
Ixodes scapularis — northeastern and midwestern US
Ixodes pacificus — western US (northern California)
Nymph stage responsible for most human infections — small size (poppy seed) reduces detection
Attachment duration ≥36 hours required for B. burgdorferi transmission in most cases
Global burden
Also endemic in Europe (Ixodes ricinus vector) and Asia
European strains: B. afzelii and B. garinii — different clinical manifestations
Pathophysiology
Causative organism
Borrelia burgdorferi sensu stricto — primary US pathogen
Spirochete: gram-negative, highly motile, obligate intracellular parasite of tick midgut
Linear chromosome — unusual bacterial genome architecture
Transmission mechanism
B. burgdorferi resides in midgut of unfed Ixodes tick
Tick feeding triggers spirochete migration to salivary glands
Transmission requires 36–48 hours of attachment for sufficient inoculation
Local innate immune response triggers expanding inflammatory reaction — EM
EM is an immunopathologic response, not direct spirochete toxicity
Spirochetes spread centrifugally — explains expanding border of EM
Dissemination mechanism
Hematogenous spread to heart (Purkinje fibers), nervous system, and joints if untreated
B. burgdorferi binds decorin on collagen — explains tropism for connective tissue
~60% of untreated patients develop disseminated disease
Immune response
IgM antibodies detectable at 2–4 weeks after infection
IgG antibodies peak at 4–8 weeks — explains low serology sensitivity in Stage 1
Antibodies persist long after treatment — complicate serologic diagnosis of reinfection
Post-treatment Lyme disease syndrome (PTLDS)
Persistent fatigue, pain, cognitive complaints after adequate antibiotic therapy
Mechanism unclear — not active infection
Prolonged antibiotic therapy not effective — IDSA strong recommendation
Therapeutic Considerations
Clinical cure rate with appropriate oral antibiotics
Rapid resolution of EM within days of initiating antibiotics
Complete symptom resolution in >90% of patients
Some patients experience Jarisch-Herxheimer-like reaction in first 24 hours
Transient worsening of symptoms: fever spike, rash expansion, myalgias
Self-limiting — not a sign of treatment failure
Antibiotic course length evidence
RCT (Stupica et al., Lancet Infectious Diseases 2023): 7 days vs 14 days doxycycline non-inferior for solitary EM
US guidelines (IDSA/AAN/ACR 2020) still recommend 10 days for doxycycline
European guidelines moving toward shorter courses
Reinfection vs treatment failure
Reinfection with a new B. burgdorferi strain is possible and should not be confused with relapse
True relapse after adequate therapy is rare
Persistent symptoms after adequate treatment are PTLDS — not an indication for re-treatment
Doxycycline and Anaplasma co-coverage
Single-drug coverage for two common coinfecting tick-borne pathogens
Clinical advantage in areas with high Anaplasma prevalence
Vaccine status
No commercially available Lyme vaccine in the US (as of 2025)
VLA15 (mRNA-based) and other candidates in late-stage clinical trials
Primary prevention relies on tick avoidance and prophylaxis
Patient Discharge Instructions
copy discharge instructions
Diagnosis and expected recovery
Diagnosis of early Lyme disease (Stage 1)
Caused by a bacterium called Borrelia burgdorferi transmitted by tick bites
With a full course of antibiotics, most patients recover quickly and completely
The rash (erythema migrans) usually begins to fade within a few days of starting antibiotics
Full resolution typically occurs within 2–4 weeks
Some temporary worsening of symptoms may occur in the first 24 hours after starting antibiotics
This is a normal response — not a sign that the treatment is not working
Antibiotic instructions
Take all prescribed antibiotics exactly as directed — complete the full course
Do not stop early even if you feel better
If taking doxycycline
Take with a full glass of water and with food or milk
Stay upright for at least 30 minutes after each dose
Avoid dairy products within 2 hours of each dose
Use sunscreen and avoid prolonged sun exposure — doxycycline causes sun sensitivity
If taking amoxicillin or cefuroxime
Take with or without food
If you develop severe diarrhea, contact your doctor — could indicate C. difficile colitis
Return to emergency department immediately for any of the following
New rashes appearing at sites away from the original bite
Facial drooping or weakness on one or both sides
Severe headache with stiff neck or sensitivity to light
Palpitations, racing or skipping heartbeat, chest pain, or fainting
Shortness of breath or lightheadedness
Joint swelling — especially the knee
Numbness, tingling, or shooting pain in the arms or legs
Fever that persists or returns after more than 24 hours on antibiotics
Tick bite prevention going forward
Use DEET-based insect repellent on exposed skin
Apply permethrin to clothing and footwear before outdoor activities
Wear long sleeves and pants tucked into socks in wooded or grassy areas
Perform full-body tick checks after every outdoor activity
Shower within 2 hours of coming indoors after outdoor exposure
Remove attached ticks promptly with fine-tipped tweezers — grasp as close to the skin as possible
Pull upward with steady, even pressure — do not twist
Clean the bite area with rubbing alcohol after removal
Check pets regularly — they can carry ticks into the home
Follow-up
Primary care follow-up in 2–4 weeks to confirm rash resolution and symptom improvement
If symptoms persist or worsen after completing antibiotics, return for re-evaluation
References
Guidelines and key sources
IDSA/AAN/ACR 2020 Lyme Disease Guidelines
Lantos PM, Rumbaugh J, Bockenstedt LK, et al.
Clinical Practice Guidelines for Prevention, Diagnosis and Treatment of Lyme Disease
Clinical Infectious Diseases 2021; Arthritis and Rheumatology 2021; Neurology 2021
PMID: 33417672
CDC Tickborne Diseases Reference Manual (2022)
Shadick N, Maher N, Hoak D.
Tickborne Diseases of the United States: A Reference Manual for Healthcare Providers, 6th Edition
United States Centers for Disease Control and Prevention 2022
Strle F, Strle K, Marques A, et al.
Lyme Borreliosis
Nature Reviews Disease Primers 2026
PMID: 41888159
Sanchez E, Vannier E, Wormser GP, Hu LT.
Diagnosis, Treatment, and Prevention of Lyme Disease, Human Granulocytic Anaplasmosis, and Babesiosis: A Review
JAMA 2016
doi: 10.1001/jama.2016.2884
Williams AL, Bevan J, Arnold MJ.
Lyme Disease: Updated Recommendations From the IDSA, AAN, and ACR
American Family Physician 2021
PMID: 34913653
Stupica D, Collinet-Adler S, Blagus R, et al.
Treatment of Erythema Migrans With Doxycycline for 7 Days Versus 14 Days in Slovenia: A Randomised Open-Label Non-Inferiority Trial
Lancet Infectious Diseases 2023
PMID: 36209759
Shapiro ED.
Lyme Disease
New England Journal of Medicine 2014
doi: 10.1056/NEJMcp1314325
Kullberg BJ, Vrijmoeth HD, van de Schoor F, Hovius JW.
Lyme Borreliosis: Diagnosis and Management
BMJ 2020
PMID: 32457042
Miller JM, Binnicker MJ, Campbell S, et al.
Guide to Utilization of the Microbiology Laboratory for Diagnosis of Infectious Diseases: 2024 Update (IDSA/ASM)
Clinical Infectious Diseases 2024
doi: 10.1093/cid/ciae104
Levin AE, Wormser GP, Horn EJ, et al.
A Novel Single-Tier Serologic Test to Diagnose All Stages of Lyme Disease
Journal of Clinical Microbiology 2025
PMID: 40833084
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 and Environmental Medicine 2021
Patel B, Malani PN.
What Is Lyme Disease?
JAMA 2025
doi: 10.1001/jama.2025.13708
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.