These are diseases are disorders caused by microorganisms such as bacteria, viruses, fungi or parasites. Many organisms live in and on our bodies. May all these organisms are not harmless or even helpful, but under positive conditions, some of the organisms may cause disease. Signs and symptoms of these infections vary depending on the organism causing the infection, but often include fever and fatigue. Mild infections may respond to home remedies and rest, while some other infections may leads to life-threatening and require hospitalization.