Viruses are very small organisms that can cause diseases like colds and flu. HIV is so small that 5,000 HIV's would fit side by side on the diameter of the period at the end of this sentence. HIV attacks the immune system, weakening its ability to protect you from certain diseases that healthy people don't usually get. This is why you don't get diseases like chicken pox more than once. But HIV tricks these guardians of health by implanting its genetic material inside them, crippling them even while multiplying itself safely within them.
Some viruses cause disease quickly.
HIV infection, after causing an initial reaction in many cases from two to six weeks after exposure, may than cause no futher symptoms for years. During all this time an infected but apparently healthy person can infect others without even knowing he or she is sick. This is the most treacherous characteristic of HIV - that millions of people will infect millions of others who will infect millions more, without anybody knowing for years that they have aquired a fatal disease. Although by the end of 1991 over 130,000 people had died of AIDS in the United States, an estimated two milliom others were infected - and infecting others. A lot of people think that no matter how bad the numbers or statistics sound, they'll be among the lucky to escape.