Sexually transmitted infections (STIs) are among the most common health concerns in Canada today. They spread mainly through unprotected sexual contact, but some can also pass from a mother to her baby during pregnancy or childbirth. Many STIs have no symptoms at first, which makes them easy to miss — and easy to spread. Understanding the basics can help you 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 pass from person to person through body fluids such as semen, vaginal fluid, blood, or saliva. In some cases, they spread through skin-to-skin contact in the genital area.
Most STIs spread during vaginal, anal, or oral sex. However, some infections — like syphilis and herpes — can spread through contact with sores or skin, even without intercourse. Sharing needles can also transmit certain infections, such as HIV and hepatitis B.
In Canada, STI rates have been rising steadily. Health Canada tracks these trends and works with provinces to improve testing and treatment access across the country. Every province and territory offers STI testing through its public health system, often at no cost to residents with a valid health card.
Common Causes of Sexually Transmitted Infections
STIs can be caused by three main types of organisms. Knowing what causes an infection helps determine the right treatment.
Bacteria: These cause infections like gonorrhea, chlamydia, and syphilis. Bacterial STIs can usually be treated and cured with antibiotics.
Viruses: These cause infections like herpes, HPV, and HIV. Viral STIs cannot be cured, but symptoms can be managed effectively with medication.
Parasites: These cause infections like trichomoniasis. Parasitic STIs are typically treatable with prescription medication.
Some infections can also pass from mother to child during pregnancy, labour, or breastfeeding. This is why prenatal STI screening is a routine part of pregnancy care under most provincial health plans in Canada.
Symptoms of Sexually Transmitted Infections
One of the most challenging things about STIs is that they often cause no symptoms at all — especially in the early stages. You can have an infection and feel completely fine. You can also pass it to a partner without knowing.
When symptoms do appear, they can vary widely depending on the type of infection. However, there are some common warning signs to watch for.
Common Symptoms to Watch For
Sores, bumps, or blisters in the genital, anal, or mouth area
Frequent or painful urination
Unusual discharge from the penis
Vaginal discharge that is heavy, foul-smelling, or unusual in texture
Vaginal bleeding between periods or after sex
Pain in the lower abdomen or during sex
Swollen lymph nodes, especially in the groin
Fever or general fatigue
Skin rashes, including on the palms or soles of the feet
Because symptoms are often absent or mild, regular testing is the only reliable way to know your STI status. This is especially important if you have new or multiple sexual partners.
The Most Common Sexually Transmitted Infections
Several sexually transmitted infections are reported frequently across Canada. Here is an overview of the most common ones, their symptoms, and what you should know about each.
1. Gonorrhea
Gonorrhea is a bacterial infection caused by Neisseria gonorrhoeae. It spreads through vaginal, anal, or oral sex. In Canada, gonorrhea rates have increased significantly over the past decade, particularly among young adults.
Women are often asymptomatic, meaning they show no symptoms at all. When symptoms do appear in women, they usually develop within the first 10 days after infection. These can include painful urination, increased vaginal discharge, and pelvic pain.
Men typically develop symptoms within 14 days of infection. The most telling sign in men is a thick, yellow or green discharge from the penis, along with burning during urination. In both sexes, gonorrhea can also infect the throat and rectum.
Without treatment, gonorrhea can lead to serious complications. In women, it can cause pelvic inflammatory disease (PID), which may lead to infertility. In men, it can cause a painful condition called epididymitis. Fortunately, gonorrhea is treatable with antibiotics, though antibiotic-resistant strains are a growing concern. Learn more from the Mayo Clinic’s guide to gonorrhea.
2. Chlamydia
Chlamydia is the most commonly reported sexually transmitted infection in Canada. It is caused by the bacterium Chlamydia trachomatis. Like gonorrhea, it often causes no symptoms, which is why it spreads so easily.
When symptoms do appear, they can closely resemble those of gonorrhea. This makes it easy to confuse the two infections. In fact, both infections often occur together in the same person.
In women, chlamydia most commonly affects the cervix and can spread to the uterus and fallopian tubes if left untreated. This can result in pelvic inflammatory disease, ectopic pregnancy, or long-term infertility. In men, urethral discharge and burning are the most common signs.
Because chlamydia is so often symptom-free, many provincial health plans cover routine chlamydia screening for sexually active individuals under age 25. Chlamydia is fully curable with a course of antibiotics.
3. Genital Herpes
Genital herpes is a lifelong viral infection caused by herpes simplex virus type 1 (HSV-1) or type 2 (HSV-2). It is extremely common, and many people who carry the virus do not know they have it.
The classic sign of genital herpes is a cluster of small blisters or sores in the genital or anal area. These sores can be painful and may take two to four weeks to heal during a first outbreak. After that, the virus stays in the body and can cause repeat outbreaks over time.
However, asymptomatic infection is actually the most common presentation. The virus can spread even when no sores are visible. This is called “viral shedding,” and it is one reason herpes is so widely transmitted.
Other symptoms during an active outbreak may include difficulty urinating, a burning or stinging sensation, fever, and swollen lymph nodes in the groin. There is no cure for herpes, but antiviral medications can reduce the frequency and severity of outbreaks and lower the risk of transmission to partners.
4. Human Papillomavirus (HPV)
HPV is the most widespread sexually transmitted infection globally. Experts estimate that about 75% of sexually active Canadians will have at least one HPV infection in their lifetime. Most infections clear up on their own without any treatment.
There are many strains of HPV. Some cause genital warts, which appear as small, flesh-coloured or pink growths in the genital area. They can range from a few millimetres to several centimetres in size and may have a cauliflower-like texture.
Other strains — particularly types 16 and 18 — are linked to cervical cancer. These high-risk strains can also cause cancers of the anus, penis, throat, and mouth. In fact, up to 10% of HPV infections occur in the mouth or throat, raising the risk of oropharyngeal cancer.
Canada has a well-established HPV vaccination programme. Most provinces offer the HPV vaccine free of charge to school-aged children through public health immunisation programmes. The vaccine is highly effective at preventing the strains most likely to cause cancer and genital warts. Talk to your family doctor about whether vaccination is right for you or your child.
5. Syphilis
Syphilis is sometimes called “the great imitator” because its symptoms can resemble many other illnesses. It is caused by the bacterium Treponema pallidum and spreads through direct contact with syphilis sores during sexual activity.
Syphilis progresses through four stages if left untreated. Each stage has different symptoms, and the infection becomes more serious over time.
Primary syphilis produces a single, painless sore called a chancre. It appears about three weeks after infection and heals on its own within three to six weeks — but the infection remains.
Secondary syphilis develops weeks to months later. This stage causes a skin rash, often on the palms of the hands and soles of the feet. Other symptoms include fever, fatigue, loss of appetite, muscle aches, hair loss, and swollen lymph nodes. Kidney, liver, and joint problems can also develop during this stage.
Latent syphilis follows secondary syphilis. During this stage, there are no symptoms at all. However, blood tests still show a positive result, and the infection can still be transmitted. Without treatment, latent syphilis can last for years.
Tertiary syphilis is the most serious stage. It can affect the heart, blood vessels, brain, and nervous system. This stage can be life-threatening. Fortunately, syphilis at any stage can be treated with penicillin or other antibiotics. Early treatment is key to preventing long-term damage. The World Health Organization’s syphilis fact sheet offers further reading on global trends and treatment guidelines.
When to See a Doctor About an STI
You should see a doctor or visit a walk-in clinic if you notice any of the symptoms described above. You should also seek care if you have had unprotected sex with a partner who has been diagnosed with an STI — even if you feel perfectly well.
In Canada, you do not need a referral to get tested for most sexually transmitted infections. Your family doctor can order STI testing, or you can walk into most community health centres or sexual health clinics without an appointment. Many clinics offer confidential and non-judgmental service.
If you do not have a family doctor, a walk-in clinic is an excellent option. Most provincial health plans cover the cost of STI testing when ordered by a physician. Some public health units also offer free or low-cost testing in the community.
Do not wait for symptoms to appear before getting tested. Regular testing is one of the most effective ways to protect your sexual health. As always, speak with your doctor or a qualified healthcare provider before making decisions about your health — they are your best resource for personalised guidance.
Treatment Options for Sexually Transmitted Infections
The good news is that most sexually transmitted infections are either curable or very manageable with the right treatment. The key is catching them early.
Bacterial STIs — such as gonorrhea, chlamydia, and syphilis — are treated with antibiotics. When taken correctly, antibiotics can fully eliminate these infections. However, it is important to complete the full course of medication, even if symptoms disappear.
Viral STIs — such as herpes, HPV, and HIV — cannot be cured. However, antiviral medications can control symptoms, reduce outbreaks, and significantly lower the risk of spreading the infection to others. Many people with well-managed viral STIs live healthy, fulfilling lives.
In addition to medication, your doctor may also recommend partner notification — letting recent sexual partners know they may have been exposed. This is an important step in stopping the spread of infection. Some provincial health units offer anonymous partner notification services if you prefer not to reach out directly.
How to Reduce Your Risk
Prevention is always better than treatment. There are several practical steps you can take to reduce your risk of sexually transmitted infections.
Use condoms consistently: Condoms reduce — but do not eliminate — the risk of most STIs when used correctly every time.
Get vaccinated: The HPV vaccine and hepatitis B vaccine are safe, effective, and available through most provincial health programmes.
Get tested regularly: Knowing your status and your partner’s status is one of the best forms of protection.
Limit the number of sexual partners: Fewer partners reduces your overall exposure risk.
Have open conversations: Talking with partners about sexual health and testing history is a responsible and caring behaviour.
Avoid sharing needles: If you use injectable drugs, access needle exchange programmes available in most Canadian cities.
No single method provides 100% protection, but combining these strategies greatly reduces your risk. Your local public health unit is a great resource for free condoms, educational materials, and information about testing locations near you.
Frequently Asked Questions About Sexually Transmitted Infections
Can you get a sexually transmitted infection without having intercourse?
Yes, some sexually transmitted infections can spread through skin-to-skin contact, oral sex, or even sharing needles — without penetrative intercourse. Herpes and HPV, for example, can spread through direct contact with infected skin or sores. Using condoms and getting regular testing are important steps regardless of the type of sexual activity.
How soon after unprotected sex should I get tested for an STI?
The timing depends on the specific sexually transmitted infection, as each has a different “window period” — the time between exposure and when a test can detect the infection. In general, it is recommended to wait at least one to two weeks before testing, though some infections like HIV may require up to 45 days. Your family doctor or walk-in clinic can advise you on the best testing timeline for your situation.
Is STI testing covered by provincial health plans in Canada?
In most Canadian provinces, STI testing ordered by a physician is covered under the provincial health plan, meaning there is no out-of-pocket cost if you have a valid health card. Some public health units and sexual health clinics also offer free testing without a health card. Contact your local public health unit to find the nearest testing location.
Can sexually transmitted infections go away on their own without treatment?
Some STIs, like certain strains of HPV, can clear up on their own as the immune system fights the infection. However, most sexually transmitted
