HIV attacks the immune system by targeting and destroying CD4+ T cells. These cells are essential for immune defense, and their depletion weakens the body's ability to fight infections and diseases. Without treatment, HIV can lead to AIDS (Acquired Immunodeficiency Syndrome), where the immune system is severely compromised.

HIV is transmitted through blood, semen, vaginal fluids, rectal fluids, and breast milk. Common modes of transmission include unprotected sexual contact, sharing of needles, and from mother to child during childbirth or breastfeeding.

The HIV genome consists of approximately 9,800 nucleotides and encodes proteins necessary for its replication and survival. Key proteins include structural proteins such as Gag and Env, enzymes like reverse transcriptase and integrase, and regulatory proteins like Tat and Rev.

Advancements in antiretroviral therapy (ART) have allowed individuals with HIV to manage the virus and live long, healthy lives. Ongoing research focuses on developing vaccines, curing the virus, and studying the mechanisms of HIV resistance and persistence. HIV's genetic diversity and rapid mutation rate make it an important subject in genomic research, contributing to better understanding of viral evolution and treatment strategies.