HIV or Human Immunodeficiency Virus is an infection which can also be transmitted through sexual activity, sharing needles and coming in contact with the blood of someone who is infected with the virus. It can also be transmitted from mother to child during child birth. HIV affects the immune system of the infected individual and destroys the white blood cells in the body making it extremely difficult for the body to fight common infections and diseases. If HIV is left untreated, it can lead to AIDS (Acquired Immunodeficiency Syndrome).
Sources:
https://www.nhs.uk/conditions/hiv-and-aids/
https://www.hiv.gov/hiv-basics/overview/about-hiv-and-aids/what-are-hiv-and-aids
https://medlineplus.gov/hivaids.html
https://www.mayoclinic.org/diseases-conditions/hiv-aids/symptoms-causes/syc-20373524
https://www.cdc.gov/hiv/basics/whatishiv.html