Toronto Public Health says 21 cases of mpox have been confirmed in the city since the start of this year compared with a total of 27 cases for all of 2023.
The health unit is encouraging eligible residents to get vaccinated against the virus formerly known as monkeypox amid the rise in cases.
It says travel is not a significant factor among the current cases, suggesting local transmission, and none of the affected individuals were fully vaccinated.
The public health unit says the virus has spread recently mostly between people who have had intimate or sexual contact, with men who have sex with men the most affected.
The virus spreads through contact with infected lesions, skin blisters, body fluids or respiratory secretions.
Symptoms can start five to 21 days after exposure and include fever, headache, muscle aches, exhaustion, swollen lymph nodes and a rash or blisters and lesions on the skin.
Individuals who are members of the LGBTQ+ community who had a confirmed sexually transmitted infection, have or are planning to have two or more sexual partners, or have attended venues for sexual contact such as sex clubs are among those eligible to receive the mpox vaccine.