Human Immunodeficiency Virus (HIV) Fact Sheet

Updated June 2025

Definition

Human Immunodeficiency Virus (HIV) is a virus that attacks and weakens the immune system. HIV is the virus that causes acquired immunodeficiency syndrome (AIDS).

Causes

HIV is transmitted through exposure to blood and/or body fluids (semen, rectal fluid, vaginal fluid, breast milk) from a person infected with HIV. Common types of exposure include:

  • Sexual exposure by having unprotected vaginal or anal sex with a person who is infected.
  • Through intravenous drug use by sharing infected needles or other drug use equipment.
  • Transmission from an infected mother to a fetus or baby during pregnancy, birth or breastfeeding.
  • Receiving infected blood or blood products (rare in Canada as blood products are checked for HIV).

Signs and Symptoms

A person with HIV may experience several stages.

  • Primary or acute HIV infection: this is the period from initial infection to the development of antibodies. Although some people have no symptoms in this stage, up to 90% of people have symptoms, including flu-like symptoms, a rash, fever, or swollen glands. Symptoms generally appear 2-6 weeks after the initial infection and are often mild, usually lasting 1-2 weeks, but may last several months. Infectivity is high during this stage.
  • Chronic asymptomatic HIV infection: this is the stage where there may be no signs or symptoms of HIV, although swollen or enlarged lymph nodes are commonly present, along with a low number of red blood cells called platelets. Many people fall into this category.
  • Chronic symptomatic HIV infection: this is the stage where the HIV virus reproduces and weakens the immune system. Symptoms may include fatigue, unexplained weight loss (more than 10% of body weight), chronic diarrhea (more than 3 weeks), unexplained fever (more than 2 weeks), or recurrent or chronic yeast infections (oral or vaginal).

Diagnosis and Tests

There are 2 types of HIV tests: a standard test where blood drawn from the vein is sent to a laboratory for testing, or a rapid/point-of-care test where a drop of blood from a finger prick is tested immediately. A standard test can detect HIV infection within 6 weeks of exposure while a rapid/point-of-care test can detect HIV within 3 months. It usually takes 2 weeks to get the results from standard testing while the results of a rapid/point-of-care test are available within minutes.

There are mainly two options for testing:

  • Nominal testing: the HIV test is ordered using the name of the person being tested.
  • Anonymous testing: the HIV test is ordered using a unique non-identifying code. The person ordering the test and providing the result does not know the identity of the person being tested. Only the person being tested knows the code, so the test result is not linked to that person’s health care record. For locations offering anonymous testing, visit Toronto Public Health Sexual Health Clinics website or call Sexual Health Infoline Ontario (SHILO) at 416-392-2437.

Complications (that may arise)

AIDS is a severe, life-threatening condition resulting from an HIV infection that goes untreated for a long time. This syndrome results from worsening damage to the immune system leading to one or more infections and/or cancers.

Treatment

While there is no cure for HIV, anti-retroviral treatment can help protect the immune system and keep HIV infection under control. The sooner treatment is started, the better for a person’s health. Medication taken as prescribed can decrease the amount of HIV in the blood so low that it’s not detectable by standard tests. When this occurs, it is not possible to pass the virus to sexual partners. This is known as U=U (undetectable = untransmittable).

Prevention

While HIV transmission can be prevented with treatment, it is still important to protect yourself against other sexually transmitted infections (STIs), including chlamydia, gonorrhea, syphilis, hepatitis B and hepatitis C. It is important to remember to use condoms correctly every time you have sex to lower your chance of getting HIV and other STIs.

If you inject drugs, you can reduce the risk of contracting or transmitting HIV by following safe injection practices such as avoiding sharing drug injection equipment.

If you share drug equipment or engage in high-risk sexual activities, HIV Pre-exposure prophylaxis (PrEP) should be taken to prevent an infection. PrEP is taken orally or by injection on an ongoing basis. If you had a high-risk exposure, HIV Post-exposure prophylaxis (PEP) should be taken as soon as possible within 72 hours. PEP is taken orally daily for 28 days. For more information, call SHILO at 416-392-2437.

Information for Sexual Partners (for STIs)

If you test positive for HIV, all of your sexual partners within the 6 weeks prior to your last negative standard (laboratory) HIV test should be notified so that they can be tested. If you have never been tested for HIV, all of your sexual partners will need to be notified to get tested.

If you do not want to tell your partner(s), a public health nurse can notify them for you. Your name will be kept confidential.

More Information

Call the Sexual Health Infoline Ontario at 416-392-2437 or 1-800-668-2437.

Safer sex: To reduce your risk of getting a sexually transmitted infection (STI), use a condom every time you have vaginal, anal or oral sex.