Packed red blood cells as anaphylaxis, red blood cell breakdown, infection, volume overload, and lung injury. With current preparation methods in the developed world the risk of viral infections such as hepatitis C and HIV/AIDS are less than one in a million. However, the risks of infection are higher in low income countries. Packed red blood cells are produced from whole blood or by apheresis. They typically last for three to six weeks. The widespread use of packed red blood cells began in the 1960s. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in
Hematopoietic stem cell Hematopoietic stem cell Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis.<ref name="Birbrair n/a–n/a"></ref> This process occurs in the red bone marrow, in the core of most bones. In embryonic development, the red bone marrow is derived from the layer of the embryo called the mesoderm. Hematopoiesis is the process by which all mature blood cells are produced. It must balance enormous production needs (the average person produces more than 500 billion blood cells every day) with the need to precisely regulate the number of each blood cell type