A sexually transmitted infection (STI) that was once thought to be a thing of the past is now a public health priority for North American doctors.

Syphilis cases skyrocketed during the COVID-19 pandemic, according to a new report from the World Health Organization (WHO).

Between 2020 and 2022, new cases of syphilis increased by 30 per cent in people ages 15 to 49 in the Americas, the WHO report indicated.

The infections recorded in North and South America in 2022 made up 42 per cent of all new cases worldwide with a rate of 6.5 cases per 1,000 people.

"There are multiple factors that have probably gotten together and caused this surge," said Monica Alonso, the unit chief for STIs at the Pan American Health Organization.

Health professionals point to factors such as a lack of awareness, low testing rates, barriers to health care, stigma and an increase in substance use.

Julian Wotherspoon, the executive director of Planned Parenthood in Regina, said one of the biggest challenges is getting STI test numbers back to pre-pandemic levels after COVID-19 prevented many patients from seeking care.

"It's not like we don't know how to identify or treat syphilis. It's that we're having trouble controlling those numbers," Wotherspoon said.

Saskatchewan posts the highest rate of syphilis cases among the Canadian provinces at 186.6 cases per 100,000, according to data from the Government of Canada. The national average rate is 36.1.

"It’s like a really bad car crash that we’re all just watching and knowing that we can prevent it," said Amanda Dela Cruz, a licensed practical nurse with Planned Parenthood Regina.

Syphilis can be diagnosed with a simple blood test. However, Dela Cruz calls syphilis "the great imitator" because it often presents symptoms common with other infections or does not show symptoms at all, which makes it difficult to self-diagnose.

If caught early, syphilis in adults is typically treated with penicillin, Dela Cruz said. But treatment becomes more "invasive" if the infection is transmitted to babies.

"The most devastating effect of syphilis in adults is congenital syphilis, which is the transmission from the mother to the fetus," Alonso said.

Because of surging syphilis cases, congenital syphilis is also on the rise. Cases in Canada jumped nearly 600 per cent from 2018 to 2022.

Dr. Jared Bullard, a paediatric infectious diseases professor at the University of Manitoba who studies congenital syphilis, said most of those cases are coming from the Prairie provinces and the territories.

However, B.C., Ontario and Quebec are starting to see an increase as well.

Bullard called the surge "significant" especially considering provinces like Manitoba went decades without recording a single case of congenital syphilis from 1977 to 2015.

"We didn't really see syphilis for decades," Bullard said.

"There's a lot of physicians and health care providers who don't really know what congenital syphilis looks like. So it's important to educate them.”

Congenital syphilis can lead to miscarriages, stillbirths and developmental issues for the baby.

Experts say pre-natal care and routine testing should be a top priority to reduce transmission.

The Canadian Paediatric Society has set out congenital syphilis guidelines on how to investigate and treat infant patients.