H.I.V. kills CD4 cells, or T-helper cells. Once the immune system is compromised, a person develops AIDS (acquired immuno-deficiency syndrome). H.I.V. is most commonly transmitted by sexual contact with an infected person. Insect bites and sweat carry almost no risk of transmission. Studies show that drying H.I.V. infected fluids can reduce viral presence by 90-99%. There is no vaccine for H.I.V. and no cure for AIDS.