MEMO: Changing Transmission Dynamics in Mpox Cases ​​​​​  

TO: Health Care Professionals in the Niagara Region       

FROM:  Clinical Services, Niagara Region Public Health

REFERENCE: Changing Transmission Dynamics in Mpox Cases

DATE: January 13, 2025

Although the mpox outbreak in Ontario was declared over in December 2022, new infections continue to be detected, suggesting ongoing transmission. To date, Niagara has had 8 confirmed cases, all in 2022. Since January 1, 2024, a total of 275 lab confirmed cases of mpox have been reported in Ontario, primarily in the Greater Toronto Area and Ottawa.  

Commonly reported risk factors include engaging in sexual or intimate contact with a partner of the same sex, with new and/or more than one partner, or anonymous partners. Public Health Ontario (PHO) has noted a recent shift in affected populations summarized below. Health care providers should be aware of changing transmission dynamics, current clinical manifestations, and testing protocols, and counsel their eligible patients to be vaccinated.

Changing Transmission Dynamics: Cases Emerging in Bridging Groups

PHO is monitoring for mpox cases that occur in “bridging groups”, defined as individuals that are not members of the predominantly affected population of men who exclusively report having sex with men.

Bridging groups include cases who:

• Identify as male and report sex with the opposite sex
• Identify as male and report both sex with the opposite sex and sex with the same sex
• Identify as female
• Less than 18 years of age with no identified risk factors

Although there is no evidence of sustained transmission among bridging groups, there has been an increase in the proportion of cases in these groups in 2024.

Clinical Manifestation and Testing

Mpox typically involves a painful rash that can occur anywhere on the body, including in the mouth and genitals. Other symptoms that can start before or after the rash include fever, chills, fatigue, swollen lymph nodes, headache, muscle aches, and sore throat. Individuals with a compatible clinical illness where mpox is suspected should be tested. Please see Testing Indications, Public Health Ontario for more information.

Vaccine

Mpox is prevented by vaccination with a two-dose series of Imvamune®, administered at least 28 days apart. Individuals who are considered high risk for exposure to mpox are encouraged to contact Niagara Region Public Health for vaccination information, including eligibility criteria.

Only 38.2% of individuals who received one dose of the Imvamune® vaccine in Ontario have received their second dose. Please encourage your patients who are at-risk for exposure to contact public health and complete their vaccine series.

In Niagara, mpox vaccine is only available at Public Health vaccination clinics. Eligible individuals can book an appointment for their first or second dose by calling 905-688-8248 or 1-888-505-6074 ext. 7425.

More Information

• PHAC – Mpox for Health Professionals
• Ontario Ministry of Health: Mpox
• Niagara Region Public Health, Mpox
• MEMO: Mpox Vaccination

To report a suspected or confirmed mpox case: Call the Infectious Disease Program at 905-688-8248 ext. 7330 or toll free at 1-888-505-6074 during business hours of Monday to Friday 8:30 a.m. to 4:30 p.m. After hours, please call 905-984-3690.