How Viruses Cause Diseases
How Viruses Spread
Viruses can cause diseases as harmless as the common cold, or as severe as AIDS.
A common way for a infectious disease to spread is through the direct transfer of bacteria, viruse, or other germs from one person or another.
Reproduction of a Virus
In order to reproduce, viruses have to rely on the organisms they invade to replicate their genes and allow them to reproduce.The virus has to invade/kill other cells in order to do this, so it would not be considered asexual reproduction.
In response to the infection, your immune system kicks in. So the coughing, headaches, and other symptoms that may occur are caused by the activities of the immune system trying to eliminate the infection.