Halifax saw a sharp increase in the number of people who tested positive for syphilis in 2012.
Last year, 59 people tested positive for the sexually transmitted infection, an increase of nearly 70 per cent in just one year.
Epidemiologist Holly D'Angelo-Scott tracks the spread of syphilis in Halifax.
"It's an outbreak. We want to stop this outbreak, so yes we are concerned," she said.
Syphilis is transmitted through oral, genital or anal sex with someone already infected with it. Symptoms include hair loss, a rash, swollen glands, and muscle and joint pain, but they can disappear on their own and the infection remains.
Cases of the sexually transmitted infection have spiked since 2008, when it was virtually unknown in the city.
Syphilis by the numbers
In 2010, there were 11 cases.
In 2011, there were 35 cases.
In 2012, there were 59 cases
So far, the syphilis cases are almost exclusively among men who have sex with men.
Health officials have been working hard to educate doctors and the public about the symptoms of syphilis, and how it's spread.
"You can transmit syphilis through oral sex and some individuals don't seem to think that oral sex is sex, and are not as aware of the transmission of syphilis via that route," said D'Angelo-Scott.
She said the increase in positive tests could be a sign that public education is working.
"So we're trying to verify that, we're trying to look to see whether or not there is been an increase in testing. That's what we're hoping."
Health officials have identified 28 places where men with syphilis first encountered their sex partners.
Some were physical locations including Citadel Hill, but more than half of the hookups were arranged online, or by using apps on smartphones.
The Capital District Health Authority said it hopes to launch a new education campaign in the spring through those same websites and apps.
"Get tested. Be aware. Know what the signs and symptoms are. Get tested so you can get treated," said D'Angelo-Scott.
She said the outbreak in Halifax mirrors patterns in other Canadian cities.