This book describes the issues of human health and healthcare from the point of view of hygiene monitoring and maintenance. Also, the perspectives on the effects of microbial cell structures, metabolism, communities and interactions on health and hygiene are included. Besides microbiological screening of patients, surfaces, air space etc. this book introduces some key bacteriological, virological and fungal risks in the clinical setting. It describes routes of contamination inside hospitals, and into our body. The means for prevention of the spreading of unwanted microbes are presented as well. Protection mechanisms of the bodily system and the balances of the human microbiome are discussed with respect to intrusions via the respiratory or digestive systems or damaged skin. The risks during operations or invasive treatments are highlighted, together with means for avoiding them. Examples of biofilm formation on the devices or on the body surfaces, latent infections, contagion mechanisms, as well as prevalent risks such as mycobacterial infections, antibiotic resistant strains, intracellular pathogens, nosocomial viruses, lowered host defences, Clostridium difficile, salmonellas, legionellas are included in the chapters of this book. Important developments such as personalized medicine, point-of-care diagnostics, arthroscopy, improved drug delivery, pre- and probiotic treatments, monitoring of the normal flora and its beneficial effects are also discussed.