HIV stands for human immunodeficiency virus and AIDS stands for acquired immunodeficiency syndrome. HIV is two species of retrovirus that infect humans. They cause AIDS, a condition that leads to the failure of the immune system, which results in life-threatening opportunistic infections and cancers. After initial infection with HIV, a person may experience a brief period of influenza-like illness or there may be a prolonged period without symptoms. HIV is a sexually transmitted infection that spreads by contact with infected blood, vaginal fluids and semen. Non-sexual transmission may also occur from infected mother to her child during pregnancy or childbirth by exposure to her blood and through breast milk. This book includes some of the vital pieces of work being conducted across the world, on various topics related to HIV and AIDS. It is compiled in such a manner, that it will provide in-depth knowledge about the current researches in this field. Scientists and students actively engaged in this field will find this book full of crucial and unexplored concepts.