Sexually transmitted infections (STIs)

The number of cases of sexually transmitted infections (STIs) is constantly growing. Anyone can get an STI without knowing it and spread it to someone else. Learn how to practise safe sex to protect yourself and other people.

What are STIs?

Sexually transmitted infections (STIs), which used to be called sexually transmitted diseases (STDs), are caused by bacteria or viruses that are generally transmitted during genital, anal or oral sex. AIDS and hepatitis B can also be transmitted through the blood.

You can have an STI without knowing it or without experiencing symptoms and spread it to your sexual partners. A number of STIs don’t necessarily cause symptoms, at least not at first. That’s why you need to practise safe sex to prevent and avoid spreading these infections.

How to prevent STIs

Use a female or male condom and a dental dam

Using female or male condoms(hyperlien vers la fiche contraception) during sex is the only way to protect yourself against STIs. No other contraception method protects against STIs.

To effectively protect yourself, you must use the condom properly and it must fit correctly. Polyurethane and latex condoms are recommended to protect yourself against STIs, and they are also a method of contraception.

If you use sex toys during sexual activity, these also need to be covered with a condom. 

To help prevent transmission through oral sex, you can cover the vulva or anus with a latex dental dam to prevent direct contact between the mouth and genitals. You can get a dental dam at a pharmacy. You can also make one by cutting a latex condom into a square. 

Note: Genital warts, herpes and syphilis can be transmitted through direct contact with sores that aren’t covered by a condom or dental dam.

Avoid at-risk behaviour

  • Having multiple sex partners increases your risk of getting an STI. If your partners have multiple partners, this makes it harder to find out their full sexual history. If you have multiple partners, you need to go to the doctor regularly to make sure any possible STIs are detected as quickly as possible.
  • Sharing needles and syringes for injectable drugs also increases your risk of contracting chronic infections such as HIV/AIDS and hepatitis B. Every year, thousands of people get infected this way.
  • Sharing personal items that may be contaminated with blood, such as razors or toothbrushes, also poses a risk of spreading certain diseases.
  • You also need to be careful when getting tattoos, acupuncture or body piercings and make sure that the instruments are single-use or have been thoroughly sterilized. 

Get vaccinated

You should also get vaccinated against human papilloma virus (HPV) infection and hepatitis A and B. Talk to your pharmacist or doctor to learn more about vaccinations for these diseases.

When to get screened for STIs

It's very important to get screened for an STI if you’ve had unprotected sex or engaged in any other at-risk behaviour. Not having symptoms doesn’t mean you don’t have an STI. Many STIs don't cause symptoms, especially at the start of the infection. Tests are available for many STIs (except for genital warts, which must be diagnosed with a physical exam).

If you are in a stable and exclusive relationship, you and your partner must also get screening tests before you stop using condoms.

What to do if you have an STI

If you have a positive result from an STI screening test, your doctor will prescribe the appropriate treatment. Some STIs can be cured (gonorrhea, chlamydia, trichomoniasis, syphilis). Others (hepatitis B, HIV, genital warts, herpes) must be treated to relieve symptoms or prevent complications, but you’ll have them for the rest of your life.

It’s very important for your health and the health of your partners that you follow the recommended treatment for the prescribed duration. Untreated STIs can have serious health consequences such as fertility problems, chronic pain, paralysis and, in the case of serious infections, even death. 
The Government of Quebec has created a program that provides free medication to treat certain STIs. When you go to a pharmacy with your health insurance card and a valid prescription for an STI treatment covered by this program, your medication will be free. For more information on this program and the list of diseases covered, visit:  

If you have an STI, it is also very important that you notify any partners that you’ve had in the previous 2 months so that they too can get screened and treated.


The human immunodeficiency virus (HIV) destroys white blood cells, which are an important part of the immune system and let the body defend itself against infections. When someone has been a carrier of HIV (HIV-positive) for a number of years without getting treated, the disease will develop into acquired immunodeficiency syndrome (AIDS).

HIV is spread through infected body fluids, e.g., blood, semen, vaginal secretions, rectal fluid, or breast milk. It can be spread:

  • Through unprotected sex.
  • Through the sharing of injectable drug needles.
  • Through the sharing of personal items soiled with infected blood or body fluids (e.g., razors, toothbrushes or sex toys).
  • From mother to child during pregnancy, childbirth or breastfeeding.

The virus isn’t viable outside the human body. It can’t be contracted from air, water, a surface or objects. It doesn’t spread in tears, sweat or saliva or in droplets from coughing or sneezing.

A doctor will make a diagnosis from a blood test that detects the virus within 3 months of transmission.

A person infected with HIV generally has no symptoms at the beginning of the disease, which progresses slowly. Over the long term, and sometimes after more than 10 years without treatment, people can experience symptoms such as unexplained weight loss, diarrhea that persists for over a month, and intense fatigue. Untreated HIV that turns into AIDS causes death, as the immune system can no longer fight off infections (cancer, pneumonia, etc.).

An HIV/AIDS infection can’t be cured. However, antiretroviral drugs or “triple therapy” can prevent the virus from reproducing and slow the progression of the disease by reducing the viral load in the blood and helping the immune system do its job.

For more information, see our article on HIV/AIDS.

Hepatitis B

Hepatitis B is caused by a virus that impairs liver function. It is spread in the same way as HIV, i.e., through contact with infected blood or body fluids. A vaccine can prevent this STI.

The symptoms of acute hepatitis B infection are:

  • fatigue
  • muscle pain
  • headache
  • sore throat
  • fever
  • nausea or vomiting
  • jaundice
  • hives
  • loss of appetite

A blood test will confirm the diagnosis. Acute hepatitis B can often go away on its own, but people will be carriers of the virus for the rest of their lives. Hepatitis B can sometimes turn into chronic hepatitis, which can cause more serious consequences like cirrhosis or cancer of the liver.

Genital warts

Genital warts are caused by the human papilloma virus (HPV). This virus is transmitted through direct skin contact with the genitals of an infected person. You can't get it from contact with a surface, such as a toilet seat. 

You can become infected without knowing it, as symptoms may appear 1 to 6 months and sometimes years after you contract the virus. You may develop small cauliflower-shaped warts on the genitals that can itch, bleed or cause pain during sex.

The diagnosis must be established by a doctor. Never try to treat genital warts with over-the-counter products. The sores can be treated with topical medications, liquid nitrogen, electrocautery or lasers. These treatments get rid of visible warts and reduce the risk of transmission. However, if you’re infected, you’ll be a carrier of the virus for the rest of your life and you may develop new sores at any time. 

There are several strains of HPV. Some types cause genital warts while others may cause genital or cervical cancers. Sexually active women must get a gynecological exam with a Pap test every 2 years to check for HPV.

A vaccine is available that protects against certain types of HPV that are responsible for genital warts and certain cancers (of the cervix, vagina, vulva, penis or anus). This vaccine is offered free of charge to girls and boys in the 4th year of primary school as part of the Québec Immunization Program.

Wearing a condom protects you against the virus, but you can still get infected if your skin comes into contact with sores that aren't covered by the condom. This is why you must treat genital warts before any sexual activity so that you don't infect your partner.


Chlamydia is caused by a bacteria that infects the genitals. Chlamydia can be transmitted through sexual intercourse (vaginal, anal or oral) and can also be spread from mother to child during childbirth. 

Nearly 40% to 70% of people infected with chlamydia have no symptoms. If symptoms occur, you may experience pain when urinating about 2 to 3 weeks after transmission. Other possible symptoms in women are abnormal vaginal bleeding, abundant vaginal secretions, pain during sex, pain in the lower abdomen, and sometimes fever and chills. Men can experience abnormal discharge from the penis, testicular pain, and itching in the penis. 

To make a diagnosis, a doctor will test vaginal secretions in women or the urethra in men or will take a urine sample.

Chlamydia is treated with antibiotics. If your doctor prescribes medication for this STI, you must take the full prescription even if you feel better before you finish the course of medication. You should also advise your sexual partners from the previous 2 months so that they can get screened. You must abstain from any kind of sex for the duration of your treatment or up to 7 days after taking a single-dose antibiotic. 

Women who are carriers of the chlamydia virus and who go untreated risk developing chronic pelvic pain. They are also more at risk of ectopic pregnancies (pregnancies outside the uterus) and fertility disorders.

Genital herpes

Genital herpes is a virus from the same family as cold sores, shingles, chickenpox and mononucleosis. In Canada, 1 out of 5 people is a carrier of the genital herpes virus, and nearly 80% to 90% of these people will never have symptoms. An infected person will have the virus for their entire lives even if they don't get sores, and they can get an outbreak at any time.

The virus is contracted from direct contact with sores. Using condoms and a dental dam will greatly reduce transmission, but the virus can still spread from contact with areas not protected by a condom and can also spread through contact with sex toys.

The virus can be transmitted from mother to child during childbirth. You should also know that oral herpes, or “cold sores,” can also spread to the genitals and cause genital herpes through oral sex.

The first episode of symptomatic genital herpes can be very painful and occurs as genital papules (small blisters) that itch or burn and may weep. These blisters then change into sores that go away in 12 to 28 days. They may also cause pain during urination, swelling in the lymph nodes in the groin, fatigue, a feeling of being generally unwell, and fever. 

When genital herpes recurs, the symptoms are much less intense and resolve in 5 to 10 days. Nearly 50% of people with genital herpes get a prodrome, or a period of warning signs before an outbreak. These signs can include shooting pain, tingling, numbness or itching where the sores will appear. The prodrome occurs 12 to 24 hours before an outbreak. You should abstain from sex during this period and whenever the sores are present, as the risk of contagion is higher during this time. You can go back to having protected sex when the sores have scabbed over.

You can't get rid of the genital herpes virus, but oral medications (antiviral drugs) are often prescribed to help sores heal and decrease pain. The dosages will differ depending on whether this is your first infection or a subsequent outbreak or if you have recurrent episodes. Once you’ve received a diagnosis and starting from the second outbreak, you need to take medication to treat your genital herpes as soon as you notice the first sores or feel the prodrome coming on.


Syphilis is caused by a bacteria and is detected with a blood test. This infection is spread through sexual contact (genital, oral or anal) whether or not the infected person has symptoms. The infection can also be spread through direct contact with skin or mucous membranes that have lesions (e.g., from kissing). The disease can also spread from mother to child during pregnancy or breastfeeding. 

Symptoms can occur 10 to 90 days after transmission. An ulcer called a “chancre” will appear in the mouth or on the breasts or genitals. A chancre usually isn't painful and therefore may go unnoticed. From 2 to 12 weeks after the chancre goes away, a roseola-like rash may appear on the trunk and neck, with patches appearing on the palms of the hands and soles of the feet. Cold-like symptoms, such as headache and fever, may also occur. If syphilis goes untreated, it can cause heart and brain problems and can even cause death in very serious cases. 

People infected with syphilis must be treated as quickly as possible if they are to make a full recovery and avoid complications. Antibiotics are used to treat the infection. The partners of infected people also need to be treated. Having syphilis increases your risk of contracting HIV.


Gonorrhea is caused by a bacteria in semen and vaginal secretions. The infection is spread during sex (vaginal, anal or oral) or from mother to child during childbirth.

Over 50% of people with gonorrhea have no symptoms. When symptoms do occur, they appear 1 to 3 weeks after transmission in women and 2 to 10 days in men. Gonorrhea can cause genital itching, pain during urination, or rectal pain or discharge. Women can also have a yellow and odourless vaginal discharge, experience abnormal bleeding during sex or between menstrual periods, or have pain during sex. For men, the other possible symptoms are a white or yellow-green discharge from the penis, or testicle discomfort or swelling.  

To detect the bacteria that causes gonorrhea, a doctor will take a urine sample or a vaginal swab in women or a urethral swab in men. If your results are positive, you must notify your partners from the previous 2 months so that they can also get tested. 

Gonorrhea is treated with antibiotics. You must abstain from any type of sex for the full antibiotic treatment or up to 7 days after taking a single-dose antibiotic. 

Gonorrhea can have serious consequences if left untreated. Women may develop a genital infection that is very likely to cause infertility or an ectopic pregnancy. Men can develop inflammation in the testicles, which can also lead to infertility. Being a carrier of gonorrhea also increases your risk of contracting HIV.


This infection is caused by a parasite that attaches to the foreskin of the penis or that can live in vaginal secretions. Symptoms of this infection can occur from 5 to 28 days after sexual activity. Men often have no symptoms, although they can experience discomfort when urinating, get inflammation at the head of the penis, or have discharge from the penis. Women can get abundant yellow-green or white vaginal secretions that have a strong smell or experience itching and pain during sex and when urinating. 

This STI is diagnosed with a blood test after a full physical exam. The infection is treated with antibiotics for all partners. Condoms can protect you against trichomoniasis.

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