As Sir Osler said, "Not examining the throat is an unforgivable mistake. A well-diagnosed clinician should have one finger in the throat and one finger in the rectum." A patient with a suspected infectious process should be thoroughly evaluated and treated promptly to prevent life-threatening consequences and complications. Furthermore, the elderly, neonates, users of certain medications, and patients with immunosuppression and comorbid diseases form a special vulnerable group, as they can be devoid of usual defensive mechanisms. On the other hand, technological advances have given rise to surgical interventions, medical devices, and other innovations, which constitute de novo sources of infection that must be ruled out in selected populations. For most patients, severe infections and sepsis comprise the sharp line between life and death. This book offers insights from a perspective that leverages the light shed by global developments. It is prepared from current sources with a realistic and simple interpretation. The targeted audience of the book are healthcare professionals, including physicians and medical students, in every environment where such patients are consulted and managed, particularly in emergency rooms and primary care organizations. Unnecessary details have been carefully omitted, as the intention is to transfer theoretical knowledge directly into practice. I wish the book to be useful to patients and all healthcare workers, who dedicate their lives to achieving equal, high-quality health for all.