Chlamydia remains Ontario’s most reported STI, syphilis cases continue climbing

Provincial health statistics show chlamydia and gonorrhea remain widespread across Ontario, while syphilis continues drawing increased public health attention.

Chlamydia remained Ontario’s most commonly reported sexually transmitted infection in the latest provincial data, with 38,478 reported cases over the last calendar year — far ahead of gonorrhea at 12,687 cases and infectious syphilis at 2,037 cases.

The numbers released by Ontario show chlamydia continuing to dominate STI reports across the province, with a rate of 234.5 cases per 100,000 people. Gonorrhea followed with a rate of 77.3 cases per 100,000.

Public health officials have also continued sounding the alarm over the steady rise in syphilis infections, both provincially and locally.

In Lambton County, local public health data showed syphilis cases climbed from just seven cases in 2018 to 45 cases in 2024, after peaking at 48 cases in 2023.

Lambton Public Health has noted that provincial surveillance data shows many people diagnosed with syphilis may also face challenges including IV drug use, housing instability, or barriers accessing healthcare services.

Provincially, Public Health Ontario previously reported infectious syphilis rates have more than tripled since 2014.

Public health officials continue encouraging regular STI testing, early treatment, condom use, and open conversations with healthcare providers as part of ongoing prevention efforts.

To access up to date information on infectious diseases in Ontario, visit Public Health Ontario’s Infectious Disease Trends in Ontario Tool