Q: It is known that HIV virus is a very labile virus. It cannot survive in adverse conditions. Then how can transmission take place through injections and syringes, used earlier by HIV infected persons, which are left in the air about an hour or so or after exposure to sunlight? Does the presence of HIV virus in the blood for 10 years or so bring about any change in the number of red blood cells, white blood cells or platelets, change in their shape or increase in the number of abnormal cells?

A:Used injection syringes have small, almost microscopic traces of blood. This blood includes the virus which can remain viable as even a blood clot has small amounts of fluids trapped in between the solid part of the clot. This can cause infection if injected into another person. The virus remains viable in blood for a long time, and clots contain fluids that preserve the virus. The rate at which the disease progresses in different persons varies. 50% of infected persons develop AIDS in a little less than 10 years after infection. As the disease progresses there are changes in the blood, a particular type of white cell, the T4 cells, start to get less in number. This can be detected by appropriate tests. Generally other types of blood cells are not changed except in the last stages of the disease.