Slow blood flow can occur if there is a narrowing of the blood vessel. This can obstruct the flow. One common cause is atherosclerosis. There are deposition of cholesterol or lipids in the wall of the arteries which can narrow it. Other causes can be an inflammation. In the veins there can be slow flow where there is difficulty in pumping blood from legs towards the heart. If you feel any symptom, you should get an examination you need to get it checked by doctor. Any query, please feel free to ask.
Retrovirus, any of a group of viruses that belong to the family Retroviridae and that characteristically carry their genetic blueprint in the form of ribonucleic acid (RNA).
A retrovirus is a virus that injects RNA into the cell, the RNA then goes through reverse-transcription. It gets turned into DNA and splices with the host cells DNA.