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Infectious Disease Control
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  1. Milestones in Public Health: Chapter 4 Infectious Disease Control Complete, Combined Lectures for Undergraduate, Graduate Public Health, and Medical and Clinical Education Levels January 2011

  2. Learning Objectives:All Learner Levels • Describe the 150-year history of world efforts to control infectious disease • Discuss Darwin’s concept of adaptation as applied to infectious diseases • Describe the roles of federal agencies and advocacy organizations • Review the CDC’s OPLAN for Avian Influenza

  3. Learning Objectives: Undergraduate Education • List the sources of infection • Describe how organisms gain entry into the body • Describe how infectious agents spread within the body • Discuss when infection occurs

  4. Learning Objectives: Graduate Public Health Education • Describe public health interventions to control communicable diseases • List the purposes of surveillance • Discuss examples of domestic surveillance • Discuss surveillance systems for MRSA

  5. Learning Objectives: Medical and Clinical Education • Distinguish between emerging and re-emerging diseases • Summarize human and microbial factors in the emergence of new infectious diseases • Describe human behaviors which play a role in re-emerging infectious diseases

  6. Lecture Outline • Historical Perspective • The Milestone and its Impact on Public Health • Aspects of Biology, Behavior and Science of Infectious Diseases • Systems, Policies and Programs • Looking Ahead • Wrap-Up • References and Resources

  7. Infectious Disease Control Historical Perspective

  8. Historical Perspective: Infectious Disease Control The War is Over! In 1967, the U.S. Surgeon General William Stewart supposedly stated: “It is time to close the book on infectious diseases, and declare the war against pestilence won.” FAQs (2004) 7

  9. Historical Perspective (Cont.) To tell the real war story, the current one, we need to go back to 1859 to Charles Darwin’s Theory of Natural Selection as the explanation of the functional designs of organisms. Neese and Williams (1996)

  10. The Concept of Adaptation by Natural Selection • Adaptations by which we combat pathogens • Adaptations of pathogens that counter our adaptations • Maladaptive but necessary costs of our adaptations Neese and Williams (1996)

  11. New Take on Darwinian Medicine • Bacteria and viruses seen as sophisticated opponents in an endlessly escalating arms race… • These pests have evolved ways to overcome our defenses or even use them to their own benefit • Explains why we cannot eradicate all infections Neese and Williams (1996)

  12. New Take on Darwinian Medicine (Cont.) From time of Darwin to those premature declarations of the end of the war against infectious disease, there is a rich history of our increasing understanding of infectious diseases and of our efforts to control them. Neese and Williams (1996)

  13. Stern and Markel (2004) Identified three eras of international approaches to controlling infectious diseases: • 1851-1881 Setting the stage: The first International Sanitary Conference • 1881-1945 Advent of germ theory and rise of bacteriology • 1945-2004 The WHO: A new definition of health to the present

  14. Growth in Understanding the Spread of Disease from Person-to-Person • Since microbes are invisible to humans, nothing was known about them until the 1600s • Microorganisms seen under microscopes of Robert Hooke (1664) and Anton Van Leeuwenhoek (1684) had to be definitively linked to disease, which was accomplished by Robert Koch in 1891 Stern and Markel (2004) and Black (2008) 14

  15. Koch’s Postulates of 1891: The Germ Theory of Disease Four fundamental concerns: 1. Microbe must be present in every case of the disease 2. Microbe must be isolated from the diseased host and grown in culture 3. Disease must be reproduced when a pure culture is introduced into a non- diseased susceptible host 4. Microbe must be recoverable from an experimentally infected host Fredricks and Relman (1996) 15

  16. Infectious Disease Control The Milestone and Its Impact on Public Health

  17. Top 10 Causes of Death (Due to Infectious Disease)by Broad Income Group WHO (2007)

  18. Populations at Risk • In the developed world, old people are most at risk of infectious diseases, while in the developing world, infants and young children remain most at risk • Other vulnerable populations to hazards of infection include immunocompromised persons and those on steroid therapy for chronic diseases Milestones (2006) 18

  19. Why Are Infectious Diseases Still Among the Leading Causes of Death Worldwide? • Emergence of new infectious diseases • Re-emergence of old infectious diseases • Persistence of intractable infectious diseases Milestones (2006))

  20. Infectious Disease Control Aspects of Biology, Behavior and Science of Infectious Diseases

  21. Aspects of Biology, Behavior and Science of Infectious Diseases Occurrence and Spread of Infection: • Infection occurs when micro-organisms invade sterile body tissues • An infectious disease occurs when infection is associated with clinically manifested tissue damage Black (2008)

  22. Sources of Infection Microorganisms enter the body through: • Air • Food • Water • Contact with skin • Contact with vectors Black (2008)

  23. Sources of Infection (Cont.) Commensal organisms (organisms that normally live in the body without causing harm): • Become pathologic because of change in host environment • Examples: • Another disease results in immunosuppression • Natural barriers breached by injury or invasive pathological processes (ulceration or malignancy) Black (2008)

  24. Sources of Infection (Cont.) • Air-borne diseases: • Many kinds of organisms enter respiratory system by inhalation of air-borne droplets • Cause infection of respiratory tract • Can also cause main impact elsewhere after spread Black (2008)

  25. Sources of Infection (Cont.) • Food-borne diseases: • Contracted from any food not preserved or isolated from potential sources of contamination • Not only cooking properly, but handling properly is important • Food handlers’ hygiene (infected or carriers) Black (2008)

  26. Sources of Infection (Cont.) • Water-borne diseases: • Usually spread by fecal-oral route • Common in less-developed countries • Also from food sources Black (2008)

  27. Sources of Infection (Cont.) • Body fluids • Organisms can be secreted in body fluids of infected person and spread by direct contact with those fluids • Mechanism of spread for sexually-transmitted diseases • Blood and blood products present risk Black (2008)

  28. How Do Organisms Gain Entry to the Body? • Examples of sites of entry • Avenues and methods used by infectious agents to get into tissues • Signs and symptoms may point to a particular site or organ system

  29. Sites of Entry • Ingestion into gastrointestinal tract • Caused by microorganisms contaminating food or water • Salmonella, Vibrio,cholera • Experience abdominal pain, nausea, vomiting, diarrhea • Inhalation into respiratory tract • Caused by microorganisms in air • Experience cough, chest pain, shortness of breath, coughing blood Black (2008)

  30. Sites of Entry (Cont.) • Ascension into urinary tract • Caused by microorganisms that enter bladder through urethra or catheter • Experience painful urination, blood in urine, pelvic pain, flank pain • Ascension into biliary tree • Caused by microorganisms entering common bile duct from GI tract • Experience abdominal pain, jaundice Uehilng, Johnson, Hopkins (1999) and Clincea, Chalasani, Gaddipati (2002)

  31. Sites of Entry (Cont.) • Crossing of mucosal surfaces • Caused by microorganisms that penetrate oral, anal, genital, or conjunctival linings • Human papillomavirus, HIV, herpes simplex virus, Neisseria gonorrhea • Experience local irritation, ulceration, pain, redness • Entrance through wound sites • Direct inoculation of microorganisms leads to direct spread Black (2008)

  32. Spread of Infectious Agents In Body • Travel via the bloodstream • Septicemia • Travel via the lymphatic system • Enlarged tender lymph nodes suggest possible infection at site • Travel via the body cavity • Can spread in cerebrospinal fluid, peritoneal fluid, joint space • Crossing the placenta to the fetus • Basis for congenital infection Black (2008)

  33. When Does Infection Occur? • Colonization: the presence of organisms on a body surface or in a lumen, but not producing disease • All persons have bacteria (and some fungi) on skin surfaces or in the oral cavity • Invasion: organisms have moved into tissues to cause disease Black (2008)

  34. When Does Infection Occur? (Cont.) • Virulence: the ability of an organism to cause infectious disease • Some organisms are unlikely to cause disease • Some organisms, like Vibrio cholera, Salmonella typhi, Mycobacterium tuberculosis, or Yersinia pestis (plague) are highly virulent and potentially fatal Black (2008)

  35. When Does Infection Occur? (Cont.) • Resistance: the ability of the host to prevent infection from occurring and infectious disease from developing • Resistance is normally aided by: • Barriers to infection: intact, functional epithelial surfaces (respiratory tract, gastric acid, antibacterial action of bladder secretions and saliva of oral cavity) • Immune system Black (2008)

  36. When Does Infection Occur? (Cont.) • Resistance is diminished by: • Debilitation from malnutrition (poor diet, alcoholism) • Cancer • Poorly functioning immune system (congenital or acquired) • Drug therapy – corticosteroids, antibiotics • Previously damaged or abnormal anatomical structure Black (2008)

  37. Infectious Disease Interventions Three major public health interventions to control communicable diseases follow: • Improved resistance to environmental hazards • Improved environmental safety • Enhanced public health systems Department of Health and Human Services

  38. Improved Resistance to Environmental Hazards • Hygiene • Nutrition • Immunity • Antibiotics • Psychological factors • Exercise • Genetic alteration Aschengrau & Seage (2008)

  39. Improved Environmental Safety • Sanitation • Air • Water • Food • Infectious agents • Vectors • Animal reservoirs Aschengrau & Seage (2008)

  40. Enhanced Public Health Systems • Access • Efficiency • Resources • Priorities • Containment • Contact tracing for prophylaxis and therapy • Education • Social forces • Laws • Measurement of problems and of the efficiency and effectiveness of control Department of Health and Human Services

  41. Four Important Systems-related Means of Controlling Communicable Disease • Containment • Contact tracing for prophylaxis and therapy • Education • Measurement (surveillance)

  42. Surveillance The ongoing systematic collection, collation, analyses, and interpretation of data and the dissemination of information to those who need to know so that action may be taken Aschengrau & Seage (2008)

  43. Purposes of Surveillance • Monitor disease trends • Monitor progress • Estimate magnitude of a problem • Detect outbreaks of an infectious disease • Evaluate interactions and programs • Identify research needs Aschengrau & Seage (2008)

  44. Surveillance is Crucial for Prevention and Control Examples of national and international surveillance programs follow: • Summary of notifiable disease (National Notifiable Disease Surveillance System) • S. aureus-related hospitalizations

  45. Domestic Surveillance: National Notifiable Disease Surveillance System (NNDSS) • Statistical summary of notifiable diseases in U.S. is published to accompany each volume of Morbidity and Mortality Weekly Report by CDC • Contains texts, graphs, and maps of official occurrences of nationally-notifiable diseases in U.S. for the year • Operated by CDC in collaboration with Council of State and Territorial Epidemiologists (CSTE) • Published in week reported CDC (2010)

  46. Domestic Surveillance: NNDDS • When published, data can be used by: • State and local health departments • Schools of public health • Communications media • Local, state, and federal agencies • Other interested agencies CDC (2010)

  47. S. Aureus-Related Hospitalizations Example of analysis of U.S.-based S. aureus-related hospitalizations using administrative databases and other surveillance sources raised possibility that majority of the overall increases in S. aureus-related discharges are due to community-associated diseases • Jhung’s Enhanced Detection of Staphylococcus aureus-related Hospitalizations Using Administrative Databases, United States, 1999-2005 Jhung (2008)

  48. S. Aureus-Related Hospitalizations (Cont.) Findings: • S. aureus-related discharges increased significantly over the period 1995-2005 • Majority of staph-related discharges due to skin infections in patients less than 45 years of age Jhung (2008)

  49. Surveillance Systems for MRSA (Methicillin-Resistant Staph Aureus) • NHSN – National Health Care Safety Network - Monitors health care-associated infections including those caused by MRSA • ABCs – Active Bacterial Care - Surveillance of the Emerging Infections Programs • From 2004-present, invasive MRSA infections are monitored in nine sites across the U.S. which currently participate in the ABC’s MRSA surveillance, represent- ing a population of 16.3 million persons • NNIS-National Nosocomial Infection Surveillance System (1970’s-2005) Publications and Reports Milestones (2006)

  50. Public Health System Capacity For surveillance system and response networks to be successful in prevention and control, the following are necessary: • Good communication among all government levels: local, state, & federal • Working across disciplines • Policy development • Planning • Training • Improved laboratory capability • Human resource capacity IOM (2003)