A condition resulting from genetic or developmental defect in the immune system is called as primary immunodeficiency, whereas if it results from exposure to various agents viz. x-radiation, exposure to certain drugs and infections, it is called secondary or acquired immunodeficiency.
By far the most common secondary, immunodeficiency is Acquired Immuno Deficiency Syndrome or AIDS, which has reached epidemic proportions particularly in Africa and western countries. It was first reported in U.S.A. in 1981 and now world-wide 35-40 million people are current infected with HIV. In India it was reported in April 1986, from Tamil Nadu but now it has spread to different parts of India. the condition is particularly alarming in North-East States. This is called as secondary immunodeficiency because AIDS virus reduces the natural immunity of the human body and hence patients become prone to many other infections or disease. Subsequently, death occurs due to secondary infection, as patient's body can't resist the attack of simple pathogens. Hence a person can die even from simple cold. It results from the infection with the Human Immunodeficiency Virus 1 (HIV-1)*. The patient infected with this experiences a number of secondary infections primarily due to the progressive destruction of immune system. This infection is very serious. the very cells that are entrusted with the responsibility of attacking the virus are taken over by the virus itself. the immune system fails because it has very few 'T' cells and ratio of helper 'T' cells to suppressor 'T' cells, normally.
