is any subjective evidence of disease, while a sign is any objective evidence of disease. For example, headache, temperature are symptoms.

Immunodeficiency (or immune deficiency)

is a state in which the immune system's ability to fight infectious disease is compromised or entirely absent.

Immune response

is how your body recognizes and defends itself against bacteria, viruses, and substances that appear foreign and harmful.

Immune system

is a system of many biological structures and processes within an organism that protects against disease.


analytical technique used to detect specific proteins in a sample of tissue homogenate or extract, process by which antigens can be separated by electrophoresis and allowed to adhere to nitrocellulose sheets where they bind nonspecifically and then are subsequently identified by staining with appropriately labeled antibodies. 

Enzyme-linked immunosorbent assay (ELISA)

is a popular format of "wet-lab" type analytic biochemistry assay that uses a solid-phase enzyme immunoassay (EIA) to detect the presence of a substance, usually an antigen, in a liquid sample or wet sample.


is a condition that results when a person ingests a substance (e.g., alcohol, cocaine, nicotine). Can be both physical and psychological. 



is a molecule capable of inducing an immune response on the part of the host organism, though sometimes antigens can be part of the host itself. In other words, an antigen is any substance that causes an immune system to produce antibodies against it.


also called immunoglobulins, are large Y-shaped proteins which function to identify and help remove foreign antigens or targets such as viruses and bacteria. 

Antiretroviral therapy (ART)

is treatment of people infected with human immunodeficiency virus (HIV) using anti-HIV drugs. ART suppress the HIV virus and stop the progression of HIV disease. ART also prevents onward transmission of HIV. ART has the potential both to reduce mortality and morbidity rates among HIV-infected people, and to improve their quality of life. 

Antiretroviral drugs

drugs, that suppress the HIV virus and stop the progression of HIV disease.


is a set of medical signs and symptoms that are correlated with each other and, often, with a specific disease.


a person having a negative result in a blood test for the AIDS virus HIV. This means that the person was not infected with HIV.


a person having a positive result in a blood test for the AIDS virus HIV. This means that the person was infected with HIV.


is a permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements.


is an epidemic of infectious disease that has spread through human populations across a large region; for instance multiple continents, or even worldwide.

Palliative care 

is a multidisciplinary approach to specialized medical care for people with serious illnesses. It focuses on providing patients with relief from the symptoms, pain, physical stress, and mental stress of a serious illness—whatever the diagnosis.

Pathogenic bacteria

bacteria that can cause infection. Although most bacteria are harmless or often beneficial, several are pathogenic. 

Risk factor

is any attribute, characteristic or exposure of an individual that increases the likelihood of developing a disease.

Risk behavior

is a lifestyle activity that places a person at increased risk of suffering a particular condition, illness or injury. 

Viral load

Viral load is the term used to describe the amount of HIV in your blood. 

Օpportunistic infection

An opportunistic infection is an infection caused by bacterial, viral, fungal, or protozoan pathogens that take advantage of a host with a weakened immune system or an altered microbiota.


Opiates are a group of drugs that are used for treating pain. They are derived from opium which comes from the poppy plant.
CD4 cells a type of white blood cells that play a major role in protecting your body from infection. They send signals to activate your body's immune response when they detect “intruders,” like viruses or bacteria.