AIDS stands for Acquired Immune Deficiency Syndrome, which is caused by the human immunodeficiency virus (HIV) that infects helper T cells and the central nervous system. HIV weakens the immune system, making one susceptible to pathogens and potentially life-threatening secondary infections, cancers, weight loss, and nervous system dysfunction. Ways to prevent the spread of AIDS include practicing abstinence or safe sex, using clean needles, screening blood for transfusion, and educating the public.