How does a razor blade used by an HIV infected person transimit the virus if l cut myself with it when it is said hiv virus does not last longer when exposed to oxygen

 
How long HIV can survive on a razor blade depends on how much fluid is present on the blade. On a relatively dry surface, HIV cannot survive for very long. However, in the presence of blood or body fluids, HIV has been known to survive for upto 7 days at room temperature, and even longer at lower temperatures. The survivability of HIV outside the body depends on many factors which cannot be quantified. The amount of virus in the fluid, the amount of fluid, and the ambient temperature are some of the factors that influence survival of HIV outside the body. HIV does survive in the presence of oxygen. What kills HIV outside the body is exposure to sunlight or heat. It cannot be determined exactly how long HIV can survive on a razor blade. This is the reason why you are advised not to share razor blades or toothbrushes or syringes and needles. Better safe than sorry.