Free · 60 Seconds · Backed by Public Health Ontario
What’s your family’s Lyme disease risk?
Free household tick-exposure assessment for GTA families. Backed by Public Health Ontario surveillance data + CDC prevention guidelines.
Question 1 of 8
Where do you live?
GTA-only — we use your specific neighbourhood’s tick surveillance data.
Quick Answer
How serious is Lyme disease in the GTA in 2026?
Lyme disease in the Greater Toronto Area has shifted from rare to actively expanding. Public Health Ontario currently flags four GTA zones as Lyme-endemic: the Oak Ridges Moraine (Caledon, King City, north Richmond Hill), Rouge National Urban Park (Scarborough, east Markham), Niagara Escarpment edge (Burlington, Halton Hills, Milton), and Hamilton-Wentworth conservation lands. Blacklegged tick populations have expanded ~20% per year in southern Ontario since 2015. Confirmed Lyme cases are now reported annually in every GTA city. The good news: Lyme is fully preventable when ticks are removed within 24-36 hours of attachment, and treatable with antibiotics when caught early. The bigger risk for most households isn’t the disease itself — it’s the gap between exposure and detection.
The four GTA Lyme-endemic zones
Public Health Ontario maintains an annual blacklegged tick surveillance program. Areas where established tick populations sustain Lyme bacterium transmission are flagged as “risk areas.”
1. Oak Ridges Moraine
Includes Caledon, King City, and northern Richmond Hill. The moraine’s mature mixed forests support large white-tailed deer populations. Lyme cases per 100,000 population in moraine-area postal codes run 3-5x the GTA average.
2. Rouge National Urban Park watershed
Covers eastern Scarborough and eastern Markham. Rouge National Urban Park is Canada’s largest urban park (79+ km²) and contains one of the highest blacklegged tick densities in any North American urban park.
3. Niagara Escarpment edge
Burlington, Halton Hills, and Milton — properties along the escarpment edge plus Bruce Trail-adjacent neighbourhoods.
4. Hamilton-Wentworth conservation lands
Cootes Paradise, Dundas Valley, and Beverly Swamp — Hamilton’s conservation lands network is one of southern Ontario’s densest tick reservoirs.
How Lyme transmission actually works
A blacklegged tick must be attached to a host for 24-36 hours minimum to transmit Lyme bacterium. The bacteria live in the tick’s midgut and need time to migrate to the salivary glands before they can be transmitted. This is why daily tick checks after outdoor activities are so effective.
Evidence-based Lyme prevention
Ranked by effectiveness in CDC and Public Health Ontario guidance:
- Reduce ticks in your yard. Health Canada-approved barrier spray reduces resident tick populations 80-90% for 21-30 days per treatment.
- Permethrin-treated clothing for hiking. Kills ticks on contact through fabric. Lasts 6 wash cycles.
- Daily tick checks after outdoor activities. Focus on hairline, behind ears, armpits, waistband, behind knees.
- Picaridin 20% on exposed skin. Repels ticks for 8 hours. Safe for kids 6 months and older.
- Shower within 2 hours of outdoor exposure.
- For dogs: Vet-prescribed oral tick prevention (NexGard, Bravecto, Simparica).
If you find a tick attached
- Remove it whole with fine-tipped tweezers — pull steady, don’t squeeze the body.
- Save the tick in a sealed plastic container with a damp paper towel.
- Submit a photo to eTick.ca for free identification.
- If it was a blacklegged tick attached >24 hours in a Lyme-endemic area, contact your family doctor about doxycycline post-exposure prophylaxis (effective within 72 hours).
- Watch for symptoms for 30 days: bullseye rash, fever, fatigue, headache, joint aches.
Sources
- Public Health Ontario — Lyme Disease Active Tick Surveillance
- CDC — Lyme Disease Information
- eTick.ca — Citizen-Science Tick Identification
Related reading
Frequently Asked Questions
How is Lyme disease risk calculated for my household?
The Lyme Risk Calculator scores 6 inputs: your GTA address (Public Health Ontario tick surveillance data identifies four Lyme-endemic zones — Oak Ridges Moraine, Rouge National Urban Park, Niagara Escarpment edge, Hamilton-Wentworth conservation lands); your yard type (wooded/leafy/open); whether you have a dog and how it is walked; whether kids play outdoors; hiking habits; tick-check behaviour; and past tick exposure history. The output is a 1-100 household-level Lyme exposure score with personalized prevention guidance.
Which GTA areas are Lyme-endemic?
Public Health Ontario currently flags four GTA zones as Lyme-endemic: (1) Oak Ridges Moraine — Caledon, King City, north Richmond Hill; (2) Rouge National Urban Park — Scarborough, east Markham; (3) Niagara Escarpment edge — Burlington, Halton Hills, Milton; (4) Hamilton-Wentworth conservation lands. Properties within 500m of any of these zones see elevated tick burden. Cases are now confirmed annually in every GTA city.
How long does a tick need to be attached to transmit Lyme?
Most research and CDC guidance states blacklegged ticks need to be attached for 24-36 hours minimum to transmit the bacterium that causes Lyme disease. The bacteria need to migrate from the tick gut to its salivary glands. This is why daily tick checks after outdoor activities are the single most effective prevention behaviour: finding and removing ticks within 24 hours essentially eliminates Lyme transmission risk.
What does early Lyme disease look like?
The classic early sign is erythema migrans — an expanding bullseye-pattern rash that appears 3-30 days after a tick bite (most commonly 7-14 days). About 70-80% of confirmed Lyme cases. Other early symptoms: fever, fatigue, headache, muscle aches, joint aches, swollen lymph nodes. If you see a bullseye rash or develop unexplained flu-like symptoms after known tick exposure, see a doctor promptly — early Lyme treats easily with 14-21 days of doxycycline.
How can I prevent Lyme disease for my family?
Five evidence-based prevention behaviours, ranked by effectiveness: (1) Reduce ticks in your yard with Health Canada-approved barrier spray; (2) Permethrin-treated clothing for hiking; (3) Daily tick checks after outdoor activities; (4) Picaridin 20% on exposed skin; (5) Shower within 2 hours of outdoor exposure to wash off unattached ticks. For dogs: NexGard, Bravecto, or Simparica oral tick preventatives.
My dog had a tick — am I at risk?
Possibly. Dogs are tick taxis — they sweep ticks up from grass and brush, then deposit them on furniture, beds, and you when you pet them. Three immediate actions: (1) Use a tick remover or fine-tipped tweezers to remove the tick whole; (2) Save the tick and submit a photo to eTick.ca for free identification; (3) Watch the dog and yourself for symptoms for 30 days.
Is the Lyme Risk Calculator a substitute for medical advice?
No. This tool provides a relative household exposure-risk score and evidence-based prevention guidance — it is educational, not diagnostic. If you have a confirmed tick bite or unexplained symptoms, contact your family doctor or local public health unit.