AIDS is an acquired immune deficiency syndrome caused by the HIV virus that severely weakens the body's immune system. It can be transmitted through unprotected sex, sharing needles, from mother to child during birth or breastfeeding, and organ transplantation. Common symptoms include fever, joint and muscle pain, fatigue, nausea, sweating, and weight loss. While there is no cure for AIDS, prevention methods include practicing safe sex, needle exchange programs, and antiretroviral therapy can suppress the virus.