Blood

"Blood is a constantly circulating fluid providing the body with nutrition, oxygen, and waste removal. Blood is mostly liquid, with numerous cells and proteins suspended in it, making blood ""thicker"" than pure water. The average person has about 5 liters (more than a gallon) of blood.
A liquid called plasma makes up about half of the content of blood. Plasma contains proteins that help blood to clot, transport substances through the blood, and perform other functions. Blood plasma also contains glucose and other dissolved nutrients.
About half of blood volume is composed of blood cells:
• Red blood cells, which carry oxygen to the tissues.
• White blood cells, which fight infections.
• Platelets, smaller cells that help blood to clot.
Blood is conducted through blood vessels (arteries and veins). Blood is prevented from clotting in the blood vessels by their smoothness, and the finely tuned balance of clotting factors."

HIV Aids

Human immunodeficiency virus infection / acquired immunodeficiency syndrome (HIV/AIDS) is a disease of the human immune system caused by the human immunodeficiency virus (HIV). AIDS is caused by HIV infection. The virus attacks the immune system leaving the individual susceptible to life-threatening infections and cancers. Common bacteria, yeast, parasites, and viruses that usually do not cause serious disease in people with healthy immune systems can turn deadly for AIDS patients. HIV is found in all the body fluids including saliva, nervous system tissue and spinal fluid, blood, semen, pre-seminal fluid, which is the liquid that comes out before ejaculation, vaginal secretions, tears and breast milk. Only blood, semen, and breast milk have been shown to transmit infection to others.
The virus is transmitted by sexual contact including unprotected oral, vaginal, and anal sex and via transfusion of contaminated blood that contains HIV.
Another mode of transmission is sharing needles or injections with HIV infected individuals. A pregnant woman can transmit the virus to her unborn baby through their shared blood circulation, or a nursing mother can transmit it to her baby in her breast milk. HIV infection does not spread by casual contact, mosquitoes, touching or hugging.