Sexually transmitted infections (STIs) are among the most common infections in Canada today. They spread mainly through sexual contact — including vaginal, oral, and anal sex — but some can also pass through shared needles, skin-to-skin contact, or from a parent to a child during birth. Understanding the symptoms, risks, and treatments can help protect your health and the health of your partners.

What Are Sexually Transmitted Infections?

Sexually transmitted infections are caused by bacteria, viruses, or parasites. They affect people of all ages, genders, and backgrounds. In Canada, STI rates have been rising steadily over the past decade, according to Health Canada.

Some STIs cause obvious symptoms right away. Others cause no symptoms at all for weeks, months, or even years. This makes regular testing very important, especially if you have more than one sexual partner.

How STIs Spread

Most sexually transmitted infections spread through direct contact with infected mucous membranes or bodily fluids. However, some — like scabies — can also spread through close physical contact or shared personal items. Using intravenous drugs with shared needles also raises your risk significantly.

Your risk of getting an STI is higher when you have multiple sexual partners, do not use condoms consistently, or have a partner who has other sexual partners. The good news is that many STIs are preventable and treatable.

Common Sexually Transmitted Infections in Canada

There are many types of STIs. Some are considered major infections because of the serious health complications they can cause. Others are classified as minor but can still affect your quality of life and long-term health. Below, we cover the most common ones Canadians should know about.

Syphilis

Syphilis is caused by a bacterium called Treponema pallidum. It progresses through stages — primary, secondary, and tertiary — and can also be passed from a pregnant person to their baby during birth. This is called congenital syphilis, and cases have been increasing across Canada in recent years.

Symptoms of Syphilis

In the primary stage, the first sign is usually a painless sore called a chancre. It appears at the site of infection — often on the genitals, anus, lips, or tongue. The sore heals on its own, but the infection remains in your body if left untreated.

In the secondary stage, symptoms appear within three to six weeks. These include a faint pink rash, flu-like symptoms such as headaches, muscle aches, and a runny nose. Some people also develop sores in the mouth or throat. If syphilis is not treated, it can progress to a tertiary stage, which can damage the heart, brain, and other organs.

A latent form of syphilis also exists, where there are no visible symptoms but blood tests come back positive. For more detailed information, visit the World Health Organization’s syphilis fact sheet.

Treatment for Syphilis

Syphilis is treated with antibiotics, most commonly penicillin. Early diagnosis leads to a much simpler and more effective course of treatment. Your sexual partners will also need to be tested and treated.

Gonorrhea

Gonorrhea is a bacterial sexually transmitted infection caused by Neisseria gonorrhoeae. It is one of the most commonly reported STIs in Canada. It spreads through direct contact with infected mucous membranes or fluids.

Symptoms of Gonorrhea

Symptoms usually appear within two to three days of exposure. These include a thick yellow-green discharge, a burning sensation when urinating, and redness or swelling around the urethra. In some people, particularly women, there may be no symptoms at all.

If gonorrhea is left untreated, symptoms may seem to disappear after about eight weeks. However, this does not mean the infection is gone. Instead, it has become chronic and can lead to complications such as prostate inflammation, urethral scarring, or fertility problems.

Treatment for Gonorrhea

Gonorrhea is treated with antibiotics prescribed by a doctor. Early treatment is straightforward and effective. However, antibiotic-resistant strains of gonorrhea are becoming more common worldwide, so it is important to follow your doctor’s exact instructions and complete the full course of medication.

Chlamydia

Chlamydia is caused by the bacterium Chlamydia trachomatis. It is the most frequently reported sexually transmitted infection in Canada and in many other developed countries. Because it often causes no noticeable symptoms, many people do not know they have it.

Symptoms of Chlamydia

When symptoms do occur, they can include pain during sex, irregular menstruation, a mild vaginal or penile discharge, a stinging or burning sensation, and discomfort when urinating. These symptoms are often mild and easy to overlook.

Chlamydia spreads through direct contact with infected mucous membranes or fluids — the same way as gonorrhea. Because it is so often symptom-free, the Mayo Clinic recommends regular STI screening for sexually active people under 25 and for others with higher risk factors.

Treatment for Chlamydia

Chlamydia is treated with a targeted course of antibiotics, typically lasting 14 to 21 days. Both partners must be treated at the same time — even if one partner has no symptoms. This prevents reinfection and helps stop the spread.

Scabies

Scabies is caused by a tiny mite called Sarcoptes scabiei. The female mite burrows under the skin and lays two to three eggs per day for about a month. This causes intense itching and a skin rash with small scratch-like marks.

How Scabies Spreads

Scabies can spread through sexual contact, but also through everyday close physical contact. Sharing towels, bedding, or clothing with an infected person can also pass on the mite. It is not exclusively a sexually transmitted infection, but it is often grouped with STIs because of how commonly it spreads through intimate contact.

Treatment for Scabies

Treatment usually involves a medicated cream or lotion applied to the entire body. All close household and sexual contacts should be treated at the same time. Washing bedding, towels, and clothing in hot water is also essential to prevent reinfestation.

HIV and AIDS

HIV (Human Immunodeficiency Virus) is one of the most serious sexually transmitted infections. It attacks the immune system over time. Without treatment, HIV can progress to AIDS (Acquired Immunodeficiency Syndrome), which leaves the body unable to fight off infections and certain cancers.

HIV spreads through unprotected sexual contact, shared needles, and from a parent to a child during birth or breastfeeding. There is currently no cure, but modern antiretroviral treatments allow people with HIV to live long, healthy lives. Early diagnosis is critical. Regular testing is encouraged for anyone who is sexually active, especially those with higher risk factors.

When to See a Doctor

You should see a doctor as soon as possible if you notice any unusual discharge, sores, rashes, burning, or itching in or around your genitals. Even if you feel fine, testing is still a good idea if you have had unprotected sex or a new partner.

In Canada, you have several options for care. You can visit your family doctor, go to a walk-in clinic, or find a sexual health clinic through your provincial health programme. Most provincial health plans cover STI testing and treatment. Many clinics also offer confidential services, so there is no reason to wait.

Remember: the sooner a sexually transmitted infection is diagnosed, the simpler and more effective the treatment. Do not rely on information from unofficial sources or treat yourself without medical guidance. A proper diagnosis always comes first.

Frequently Asked Questions About Sexually Transmitted Infections

What are the most common sexually transmitted infections in Canada?

The most common sexually transmitted infections in Canada are chlamydia, gonorrhea, and syphilis. Chlamydia is the most frequently reported STI nationally. HIV also remains a serious public health concern across all provinces and territories.

Can you have a sexually transmitted infection with no symptoms?

Yes, many sexually transmitted infections — including chlamydia and HIV — can be present with no noticeable symptoms. This is why regular testing is so important, especially if you have a new or multiple sexual partners. You can have an STI and unknowingly pass it to others.

How can I get tested for STIs in Canada?

You can get tested for sexually transmitted infections through your family doctor, a walk-in clinic, or a sexual health centre in your community. Most provincial health plans cover STI testing at no cost to you. Testing is confidential and straightforward.

Do both partners need to be treated for an STI?

Yes, in most cases both sexual partners need to be tested and treated for a sexually transmitted infection, even if one person has no symptoms. Treating only one partner can lead to reinfection. Your doctor will advise you on the right approach for your specific situation.

How can I protect myself from sexually transmitted infections?

Using condoms consistently and correctly is one of the most effective ways to reduce your risk of sexually transmitted infections. Limiting the number of sexual partners, getting vaccinated where available (for example, HPV and hepatitis B), and having regular STI screenings also help protect your health.

Can sexually transmitted infections be cured?

Many sexually transmitted infections caused by bacteria — such as chlamydia, gonorrhea, and syphilis — can be fully cured with the right antibiotic treatment. Viral STIs like HIV and herpes cannot be cured, but they can be managed effectively with medication. Early diagnosis always leads to better outcomes.

Key Takeaways

  • Sexually transmitted infections are common in Canada and affect people of all backgrounds.

  • Many STIs — including chlamydia and HIV — cause no symptoms, making regular testing essential.

  • Syphilis, gonorrhea, and chlamydia are bacterial STIs that are treatable with antibiotics when caught early.

  • Both partners must be tested and treated to prevent reinfection.

  • Always complete the full course of any prescribed treatment, even if symptoms disappear.

  • Condoms, regular screenings, and open communication with your partner are your best defences.

  • If you have concerns, speak with your family doctor, walk-in clinic, or provincial sexual health centre — testing is confidential and usually covered by your provincial health plan.

This article is for informational purposes only and does not replace professional medical advice. Always consult your doctor or a qualified healthcare provider for diagnosis and treatment tailored to your situation.