<span>There are three parts of the body that will change suggesting a systemic disease. The first is the hands, which contain may blood vessels and a significant amount of skin surface. Nerves in the body might show signs of a systemic disease. Finally, muscles, tendons and ligaments might swell or otherwise show signs of bodily stress.</span>
The formation of new viruses.
Have a control. You have to have something to compare your experimental results or else your results could be random chance.
