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revised Friday February 17 2023

Lyme Disease | West Nile Virus | Eastern Equine Encephalitis



Lyme Disease at-a-Glance

Lyme disease:

  • Is a bacterial illness that is spread to people and animals through tick bites.
  • Was first identified in 1975 in Lyme, Connecticut.
  • Can affect your joints, heart and nervous system.
  • Happens in phases.
  • Is treated with antibiotics.

Lyme disease is a vector-borne disease.

A vector-borne disease spreads to humans or animals through insects called vectors.

Vector-Borne Disease Plans

Signs and symptoms

Lyme disease symptoms happen in 3 stages; however, not all people infected will have symptoms of each stage.

Stage 1

Erythema Migrans
Erythema migrans, the rash characteristic of Lyme disease

The first sign of a Lyme disease infection is usually a circular rash called erythema migrans (EM). EM happens in about 70-80% of people infected with Lyme disease. It appears at the site of the tick bite 3 days to 1 month after a person is bitten.

If you have Lyme disease, you might also have or feel:

  • fatigue
  • chills
  • a fever
  • a headache
  • muscle and joint pain
  • swollen lymph nodes

Stage 2

If the infection isn’t treated, the second stage of the disease can last for several months.

During this stage you might have or feel:  

  • nervous system disorders
  • multiple skin rashes
  • arthritis and arthritic symptoms
  • heart palpitations (a pounding or racing heart, or like your heart is skipping)
  • severe fatigue and general weakness

Stage 3

If the infection continues to go untreated, the third stage of the disease can last months to even years. Chronic arthritis and neurological symptoms can both be signs of stage 3 Lyme disease.

If you’re experiencing any of these symptoms and think you might have Lyme disease, book an appointment with your doctor.

* Adapted from the Public Health Agency of Canada’s Lyme Disease Fact Sheet


A bacterium called Borrelia burgdorferi causes Lyme disease.

Black-legged Tick
Black-legged Tick (Ixodes scapularis)

The Lyme disease bacterium, Borrelia burgdorferi can be carried in mice, squirrels, birds and other small animals. The bacterium spreads to ticks when the ticks feed on these infected animals. Lyme disease is spread to people by these ticks when they bite the skin and start to feed on the host’s blood, which lets the bacterium infect the body.

In Ontario, the black-legged tick (Ixodes scapularis) spreads Lyme disease to people and other animals. The black-legged tick is also known as the deer tick.

Lyme disease can infect animals we live in close contact with, such as dogs and cats. However, most of these animals don’t show symptoms and are diagnosed through routine blood tests.


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Revised: Friday February 17 2023

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