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HIV and AIDS Glossary


HIV, or the Human Immunodeficiency Virus, is a virus that damages the immune system of the infected person. It´s a chronic virus infection and it requires regular medical monitoring and permanent medical treatment. The virus attacks certain white blood cells and destroys them. It evolves quickly, which makes it difficult to destroy with medication. The immune system of people living with HIV weakens little by little, and without proper medication they will be exposed to numerous different illnesses.


Acquired Immunodeficiency Syndrome
AIDS is the stage of the HIV infection where the immune system has clearly deteriorated and the body is less able to resist diseases. With current treatment methods, it is possible for the illness to return from the AIDS phase back to HIV, and AIDS patients do not always die of AIDS-related diseases any more. Living with HIV does not mean having AIDS.


The body of a person living with HIV begins to produce antibodies against the HI virus soon after contagion. All people with an HIV infection develop antibodies which are detectable in tests within three months from contagion. Most of the time an HIV test will show antibodies already after one month of contagion. HIV is diagnosed based on the finding HIV antibodies in a person’s body.

Usually the antibody test is taken from vein blood from the arm or from a blood sample from the fingertip. A person with an early HIV infection can transmit the virus even before the antibodies show up in a test. If the antibody test has been done after three months of exposure to HIV and it shows a negative result, it means that the person does not have an HIV infection.


The antigen of HIV is a protein in the HI virus, which can be detected with a specific test from the blood sample of a person with HIV. With around half of HIV positive people, antigens can be detected from blood within the first few weeks from contagion or if they develop AIDS, but not otherwise. For the other half of people with HIV, antigens are never found, so a negative antigen test result is not reliable on its own. The antigen test is often used in a combined test, which searches for HIV antibodies as well as antigens. Using the combination test is justified when an early infection is suspected, in which case HIV antibodies have not formed yet, but antigens could be discoverable.

Blood contact

Blood contact refers to a situation where a person has been exposed to another person’s blood. HIV can be transmitted from a person to another through blood either through intravenous drug use or through blood transfusion or organ transplants.

CD4 cell

A helper cell that regulates the functions of the immune system by detecting substances foreign to the body and by helping other lymphocytes in destroying pathogens. The amount of CD4 cells in the body indicate, along with other lab tests, how the HIV infection is progressing.

HIV risk

HIV risk refers to a situation where a person has been exposed to the HI virus. Such situations include oral, vaginal and anal sex, which has not involved using a condom the whole time or if the condom has broken. Other situations are blood exposure as well as sharing needles and syringes.

Mucous membrane contact

Mucous membrane contact refers to the physical contact of human mucous membranes. Mucous membrane contact is formed during unprotected oral, vaginal or anal sex. HIV can be transmitted in the above-mentioned mucous membrane contacts, but not through kissing.


Polymerase Chain Reaction, a form of laboratory test that detects e.g. the genomes of the HI virus in blood plasma. The test is used before beginning medical treatment, in monitoring the medical treatment as well as for detecting possible medication-resistant virus strains. The method is very important for monitoring the efficiency of HIV medication. PCR tests are not used for diagnosing HIV infections.

Preventive medical treatment

A person exposed to HIV can be treated with a specific preventive medication, known also as post-exposure prophylaxis or PEP. PEP is considered when a person has been in sexual contact with an HIV positive person without a condom and the condom has broken. The person exposed to HIV should start the treatment within 48-72 hours after exposure. The need for preventive medical treatment is evaluated by an infectious disease doctor.

Primary HIV infection, or acute HIV infection

Around 30–50% of HIV-infected people are affected by a primary HIV infection within 2–6 weeks from contracting the virus. The symptoms are much like a common cold: fever, a sore throat, swollen lymph nodes and so forth. Some people get a rash on their upper body. An HIV infection cannot be diagnosed based on the symptoms. Only an HIV test can provide reliable results on whether one is infected or not.

Rapid test

The HIV rapid tests deliver results in 1–20 minutes depending on the product used. It tests for HIV antibodies (HIVab) or antigens and antibodies (HIV AgAb). The rapid test uses blood for detecting antibodies or antigens. At the moment, all quick tests available on the market are not reliable. It is therefore advised to get oneself tested at a health care office. A negative result from a rapid test is reliable, when it has been three months since the possible contagion.

Risk situation

In connection with HIV, risk situations are often mentioned. Risk situations refer to situations where HIV or some other sexually transmitted infection (STI) could have been transmitted, such as during sexual contact or blood transmission. It is important to properly describe the risk situation for the tester to evaluate how and when to conduct the test in order to get a reliable result.

Serological window period

An HIV infection is diagnosed through HIV serology by determining antibodies. It may take up to three months for the body to produce antibodies caused by the HI virus. The window period refers to the period after contraction during which the person with an infection is able to transmit the disease, but no antibodies are yet detectable in lab tests. Most people with HIV do show positive results within a month from contraction.

Sub-types of the HI virus

There are two types of HI viruses, which are called HIV-1 and HIV-2. Both forms have further sub-types of their own. Both sub-types can be detected in HIV tests three months after contraction.

T cell

Lymph cell or lymphocyte cell, a type of white blood cell that plays a central role in maintaining the body’s immune system. The HI virus weakens and destroys the helper T lymphocytes’ functions in the body. See also: CD4 cell.


Viral Load, a value calculated with lab methods, which indicates the amount of HI viruses in the blood circulation. The amount of viruses and other lab tests help to determine the status of the HIV infection in the body. The viral load becomes undetectable when the person with HIV is on effective medication, which means that sexual contact can no longer spread the infection.