HIV-1 is the most common form of human immunodeficiency virus. It mainly targets immune cells, particularly CD4 T-cells, and if left untreated, it can gradually weaken the immune system over time. HIV-1 is the principal cause of the global HIV epidemic and is the type most people mean when they say “HIV”.

HIV-1 is a virus that infects and damages cells in the immune system. Over time, a decreasing number of CD4 T-cells can reduce the body’s ability to fight infections. Without treatment, HIV infection can progress to AIDS (acquired immunodeficiency syndrome), which is the advanced stage of HIV infection.
HIV-1 can be transmitted through exposure to infected blood, semen, vaginal fluids, and breast milk. Common transmission routes include unprotected sexual contact, sharing needles or syringes, and from mother to child during pregnancy, childbirth, or breastfeeding. It is not spread through casual contact such as hugging, sharing cutlery, or using the same toilet.
Self-tests like this one detect antibodies produced by the immune system in response to HIV-1 (and HIV-2). Antibodies are not always detectable straight away after exposure, which is why timing matters.
After a possible exposure, it may take some time before antibodies reach detectable levels. During this “window period,” a test can be negative even if infection has taken place. If exposure was recent, it is important to repeat testing later and/or seek medical advice for appropriate follow-up.
