How fast is blood replaced in the body?

Question

I'm a writer, and I require some details for my writing. I've included the circumstances for my question below, in case they can help you answer the question.

In my current project, I'm dealing with a disease that slowly replaces the blood cells of the human body with its own infectious replicas. These cells serve the same purpose as red blood cells, with the distinct disadvantage that they keep the body infected. In all other aspects, they are essentially red blood cells.

In addition to this, the disease eventually works its way into the bone marrow, stopping it from manufacturing red blood cells altogether. Instead, the bone marrow is forced to create more of the replicas.

The only way to cure an infected person (that I can see) would be to somehow cure the bone marrow and get it to produce red blood cells again. It is my understanding that blood cells are constantly dying and being reproduced, so repairing the bone marrow would eventually result in the bloodstream being repopulated with red blood cells, and the replicas dying out.

Question: On that note, how long would it take the human body to completely replace its blood supply? Or is this even possible?

Answer 1

Calculating from the numbers Wikipedia's articles on bone marrow and red blood cells, the bone marrow in an adult human produces between 200 billion and 500 billion red blood cells a day, taking between 60 and 120 days to produce enough to replace the 20-30 trillion red blood cells in circulation. Under normal conditions, red blood cells wear out and are replaced on a 120-day cycle; presumably the faster production rate is for dealing with injuries or other abnormal loss of RBCs.