SIV is the abbreviation of

Explanation

SIV stands for Simian Immunodeficiency Virus, which is a retrovirus that infects non-human primates such as monkeys and chimpanzees. It is closely related to the Human Immunodeficiency Virus (HIV) and is considered its precursor, as cross-species transmission of SIV from primates to humans is believed to have led to the emergence of HIV-1 and HIV-2. Like HIV, SIV attacks the immune system, particularly CD4+ T cells, leading to immunodeficiency in its hosts.