Infectious diseases remain the second leading cause of death worldwide. Despite numerous advances in the diagnosis, treatment, and prevention of infectious diseases, threats of antimicrobial resistance, and emerging/reemerging infectious diseases continue to pose challenges.
- Multidrug resistance has been increasing in prevalence in recent years and differs among different geographical regions and among institutions in the same area. The overall prevalence of antimicrobial resistance is affected by reservoirs in the pt population, use of antimicrobial drugs that favor resistant strains, and transmission of resistant strains to pts from their environment or other persons (e.g., health care workers with poor hand hygiene).
- The Centers for Disease Control and Prevention (CDC) has estimated that >2 million resistant bacterial infections occur in the United States each year, with 23,000 deaths, and has identified particular resistant pathogens that are of greatest concern, given their impact on public health (Table 80-1 Antibiotic Resistance Threats in the United States, 2013 ).
- Bacteria circumvent the activity of antibacterial agents by mechanisms that generally fall into three categories: (1) alteration or bypassing of targets that exhibit reduced binding of the drug, (2) altered access of the drug to its target by reductions in uptake or increases in active efflux, and (3) a modification of the drug that reduces its activity (Table 80-2 The Most Common Mechanisms of Resistance to Antibacterial Agents ).
- The CDC has emphasized four actions to address the growing problem of antimicrobial resistance: (1) prevent infections, (2) track resistance patterns, (3) improve use of existing antimicrobial agents, and (4) develop new antimicrobial drugs and diagnostic tests.
Emerging/Reemerging Infectious Diseases 
- Infectious diseases are considered to be emerging if the incidence in humans has increased within the past two decades or is anticipated to increase in the near future.
- Reemerging infectious diseases are those that were previously under control but have more recently increased-or are expected to increase-in incidence.
- Reasons for disease emergence or reemergence include human demographics and behavior, technology and industry, economic development and land use, international travel and commerce, microbial adaptation and change, and breakdown of public health measures.
- Examples of emerging and reemerging infectious diseases, as of 2017, are listed in Table 80-3 Examples of Emerging and Reemerging Infectious Diseases .