In this edition of the Emerging Infectious Diseases of the 21st Century Series, the editor reviews the research, diagsis, and treatment of some common infections facing researchers, clinicians and family physicians such as sinusitis, otitis media and pertussis in adults. Recent studies and surveys have shown that these conditions are often over diagsed and treated unnecessarily with antibiotics. The approach and guidelines for diagsis and management are reviewed in this volume. Other more complicated but less common conditions challenging internists, clinical infectious disease consultants and other specialists are also reviewed (i.e. meningitis, ventilator associated pneumonia, sepsis, hepatitis C, B, etc.).