Epidemiology of Emerging Infectious Diseases: Global Threats to ...

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  • The purpose of this lecture is to acquaint the student with basic epidemiological features of emerging / reemerging infectious diseases in terms of global burden, etiology, and international response.
    NB: A selected bibliography of this lecture is available from the author.
  • Health of the global community is directly influenced by a number of factors, both natural and man-made, most of which exhibit a Malthusian character.
  • Over the years, prominent health concerns have shifted from infectious diseases to chronic, behavior-related diseases. However, contemporary thought must include an examination of infectious disease control.
    One of the more contemporary threats to well-being is the issue of emerging infectious diseases, a relative new-comer to the study of public health.
  • HIV/AIDS is one example of an emerging infectious disease (EID). The Institute of Medicine (1992) defines EIDs to include diseases whose rates of incidence have increased within the previous two years or those with the potential of rate increases in the near future.
    Emerging infectious diseases are relatively new diseases (Legionnaire’s disease and ebola, for example) whereas reemerging infectious diseases are those whose incidence has increased after a period of control (cholera and tuberculosis).
  • Since 1973, a number of new pathogenic microbes have emerged worldwide among human populations. Among them, ebola virus, E. coli O157:h7, H. Pylori, and hantavirus.
  • The emergence of HIV/AIDS in 1981, increases in dengue and diphtheria cases in Latin America, increases in cholera cases all serve to illustrate the problematic nature of infectious disease.
  • Cholera
  • Dengue
  • Diarrheal Diseases
  • Diphtheria
  • This chart illustrates the impact of political transition on the prevalence of diphtheria in the former Soviet Union.
  • Escherichia coli O157:H7
  • Ebola
  • The global impact of Ebola virus
  • Hantavirus
  • Helicobacter pylori
    H. pylori is an excellent example of how an infectious organism is related to a chronic disease, in this case gastric cancer.
  • Listeriosis
  • Malaria
  • Tuberculosis
  • Tuberculosis
  • TB cases, U.S., 1953-1999
  • West Nile Encephalitis
  • A number of reasons have been offered to explain the emergence of new pathogenic organisms. The Institute of Medicine offers an explanation above.
  • One of the most important medical issues related to emerging infections is the concern of drug resistance. Examples include strains of gonorrhea, and malarial infections that are now resistant to traditional drugs. Multi-drug-resistant tuberculosis is also a concern.
    Perhaps the primary reason for drug resistance is the 1) inappropriate use of “silver bullets” or antibiotics on the part of the patient (compliance) and 2) over prescription of medications on the part of the physician.
  • There is overwhelming evidence that many chronic diseases have a causal relationship with infectious diseases. Examples include HPV and skin cancer, as well as cervical cancer in females, Epstein-Barr virus and non Hodgkin's lymphoma, and hepatitis B virus and liver cancer. These associations serve only to exacerbate the global threat of disease emergence / reemergence.
  • Many international organizations have developed plans of action specific to EIDs. The response by the Centers for Disease Control and Prevention includes four broad goals.
  • In order to combat emerging infectious diseases, a number of public health measures must be augmented or continued. At the forefront of prevention is public health education. Members of the global community should be educated about EIDs as well as vaccinated against them where possible. Nations of the world should also pool their financial as well as academic resources. Finally, additional governmental funding should be offered to combat the threat of emerging infectious diseases.
  • Conclusions
  • Useful Documents
  • Useful Sites
  • Epidemiology of Emerging Infectious Diseases: Global Threats to ...

    1. 1. Epidemiology of Emerging InfectiousEpidemiology of Emerging Infectious Diseases: An Examination of GlobalDiseases: An Examination of Global Threats From a Public HealthThreats From a Public Health Education PerspectiveEducation Perspective Dr. B. McKinley ThomasDr. B. McKinley Thomas Assistant Professor of EducationAssistant Professor of Education Department of Kinesiology and Health ScienceDepartment of Kinesiology and Health Science Augusta State UniversityAugusta State University Email: bthomas@aug.edu
    2. 2. About the Author Dr. B. McKinley Thomas is a public health educator in the Department of Kinesiology and Health Science at Augusta State University, Georgia, USA. He graduated with a Doctorate of Education in 1995 from the University of Tennessee. Post doctorate work was completed with the University of South Carolina, School of Public Health, Eastern Carolina HIV Prevention Collaboration. The authors research interest include HIV/AIDS, trend analysis of mortality / morbidity data, and the global impact of suicide among elderly females.
    3. 3. Performance Tasks  define emerging infectious diseases.  list infectious agents that pose a major threat to public health.  discuss the etiology of emerging infectious diseases.  acknowledge CDC’s response to emerging infectious diseases.  generate ideas regarding future trends and issues.  locate internet resources in the area of infectious disease control.
    4. 4. Public Health Issues / Concerns  International relations  Political collaboration  Nuclearization  Food shortages  Equity  Life expectancy  Data Validity  Violence  Reproduction and birth control  Chronic diseases  Warfare  Mortality / Morbidity  Injury
    5. 5. Infectious Disease  1900 - Leading Causes of Death – Tuberculosis – Pneumonia and Influenza – Heart Disease – Diarrhea / Enteritis – Cerebrovascular Disease – Nephritis / Nephrosis – Unintended Injury – Cancer – Diphtheria – Typhoid Fever  1992 - Leading Causes of Death – Heart Disease – Cancer – Cerebrovascular Disease – COPD – Unintended Injury – Pneumonia / Influenza – Diabetes Mellitus – HIV/AIDS – Suicide – Homicide / Legal Intervention
    6. 6. Emerging Infectious Diseases (EID) Defined Defined to include diseases with rates of incidence that have increased within the last two years or those with the potential of increasing in the future Institute of Medicine, 1992
    7. 7. Pathogenic Microbes Identified as Threats to Humans Since 1973  1973 - Rotavirus  1977 - Ebola virus  1977 - Legionella pneumophila  1980 - HTLV 1  1981 -Toxin-producing Staphylococcus aureus  1982 - Escherichia coli O157:H7  1982 - Borrelia burgdorferi  1983 - HIV  1983 - Helicobacter pylori  1989 - Hepatitis C  1992 - Vibrio cholerae O139  1993 - Hantavirus  1994 - Cryptosporidium  1996 - nvCJD  1997 - HVN1 CIA, 2000
    8. 8. Examples of Problem Scope  1981 – The emergence of HIV/AIDS  1994 – More than 200,000 cases of Dengue reported in Latin America and a 140% increase (over 1990) of diphtheria in the same region.  1995 – Reports a four-fold increase in cholera levels over 1990 estimates.  Estimated, 25% of all U.S. Doctor visits each year due to complications associated with infectious diseases.
    9. 9. Cholera  Vibrio cholerae  Sub-Saharan Africa affected – Democratic Republic of Congo – Uganda – Rwanda – Burundi – Tanzania – Kenya – Sierra Leone – Cameroon  Over a 3 month period in 1997 outbreaks in Kenya & Tanzania, over 400 killed  Cases reported in 2000 – Federated States of Micronesia 954 cases / 9 deaths – Somalia 2,232 cases / 230 deaths – Madagascar 15,173 cases / 860 deaths
    10. 10. Dengue  Most important mosquito-borne disease, worldwide  Aedes aegypti  Affected regions – Indian Subcontinent – Southeast Asia – Southern China – Central and South America – Caribbean – Mexico – Africa  Symptoms similar to those of influenza
    11. 11. Diarrheal Diseases  Organisms most frequently associated with diarrhea in young children / estimated percentage of cases seen at health centers in the developing countries – Rotavirus - 15-25% – Enterotoxigenic Escherichia coli - 10-20% – Shigella - 5-15% – Salmonella (non-typhoid) - 1-5% – Campylobacter jejuni - 10-15% – Cryptosporidium - 5-15% (PAHO, 2000)  Oral rehydration therapy (ORT) is one way of combating diseases within this classification
    12. 12. Diphtheria  Corynebacterium diphtheriae  Good example of how political issues can influence the reemergence of a disease –[See following graph]  Very contagious and potentially life- threatening  Large epidemics in the Soviet Republics, Algeria, China, and Ecuador.
    13. 13. Source: Morbidity and Mortality Weekly Report. (1996). August 16, 1996 / 45(32);693-697
    14. 14. Escherichia coli O157:H7  Food-borne  First recognized as a cause of illness in 1982 during an outbreak of severe bloody diarrhea  Annually – 73,000 cases – 61 deaths  Primarily transmitted via ingestion of meat that has not been properly cooked  Person-to-person, contaminated drinking water, consumption of contaminated plant products (CDC, 20006)
    15. 15. Ebola  Filovirus  Fifteen global outbreaks since 1967 Breman, van der Groen, Peters, & Haymann (1997)  Major human outbreaks –Sub-Saharan Africa Kikwit Zaire Sudan Gabon
    16. 16. Ebola Virus and the Global Community Year Location Cases Fatality 67 Germany 2 Unsure 76 Sudan 280 53 76 Zaire 318 90 77 Zaire 1 100 79 Sudan 34 65 89 U.S. 4 65 95 Zaire 393 79 Source: Benini, A. A, & Bradford, 2000
    17. 17. Hantavirus  Also known as... – Sin Nombre virus (responsible for most hantaviral infections in the U.S.) Wells, et al, (1997) – Convict Creek virus – Muerto Canyon virus  First recognized in 1993 – Four corners region of the U.S. – Has been identified in the U.S. from CA to FL  Mortality rate, 50%  Associated disease – Hantavirus pulmonary syndrome (HPS)
    18. 18. Helicobacter pylori  Bacterium  Believed to be the etiologic agent in –90% of duodenal ulcers –80% of gastric ulcers  Discovered as culprit in 1982  Large portion of world population infected  Related chronic disease –Gastric cancer
    19. 19. Listeriosis  Listeria monocytogenes  Common among individuals who work with animals  Causes spontaneous abortion and stillbirth in domestic animals  Primarily affects – Pregnant women – Newborns – Elderly – Immuno compromised adults (Canadian Institute of Public Health Inspectors, 2000)
    20. 20. Malaria  Due to Plasmodium parasite transmitted by the  Anopheles mosquito  300 million infected each year  Regions – Asia – Africa – South / Central Americas  >1 million deaths annually – Mostly infants and children (National Institutes of Health, 2000)
    21. 21. Tuberculosis  Chronic bacterial infection  Principal infectious cause of death worldwide – Three million deaths annually – One-third of world population infected with M. Tuberculosis (OSHA, 2000)  Outbreak locations – Jails / prisons – Hospitals – Nursing homes – Homeless shelters
    22. 22. Tuberculosis  Estimated 15 million Americans with latent infections  Minorities affected disproportionately [as is the case with many other infectious diseases] –54% active M. Tuberculosis cases (1995) reported among African American and Hispanic populations –An additional 17.5% among Asians  In some U.S. sectors, morbidity rates surpass those of poorest countries
    23. 23. Cases of M. Tuberculosis by Year of Diagnosis, 1953-1999 0 10,000 20,000 30,000 40,000 50,000 60,000 70,000 80,000 90,000 1953 1955 1957 1959 1961 1963 1965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 Source: Centers for Disease Control and Prevention, 20001
    24. 24. West Nile Encephalitis  Mosquito-borne infection  Outbreaks evident in Egypt, Asia, Israel, South Africa, parts of Europe and Australia  No recorded cases in the U.S. prior to 1999  Culex pipiens mosquito (the common house mosquito) associated with West Nile virus  Transmission: Bird ---> mosquito ---> human – American crows most commonly infected, yet confirmed in other species (State of New York, Department of Health, 2000) – May also infect other mammals such as horses – 62 cases 7 deaths
    25. 25. Institute of Medicine  Demographic shifts  Advances in technology / industry  Economic development and change in land use patterns  Travel / commerce  Microbial adaptation / change  Breakdown of the public health infrastructure
    26. 26. Drug Resistance  Drug Resistance – Gonorrhea, malaria, childhood ear infections – Resistance is a factor in most nosocomial infections – More effective medications are needed In some U.S. clinics, 30% of cases of gonorrhea resistant to penicillin or tetracycline or both – MDR-TB  Inappropriate use of antibiotics is a salient factor in drug resistance
    27. 27. Infectious Diseases and Chronic Diseases  Emerging evidence that a substantial proportion of human cancers are caused by infectious diseases (~15%) (Valerie Beal, Speaker, 2nd International Conference on Emerging Infectious Diseases) – 1911 - Rous Sarcoma – 1932 - Shope Skin Tumor – 1960 - Feline Leukemia – 1978 - HPV, Skin Cancer – 1981 - HBV, Liver Cancer – 1981 - EBV, non Hodgkin's Lymphoma – 1983 - HPV, Cervical Cancer
    28. 28. CDC’s Response to EIDs Goal I: Surveillance and Response Goal II: Applied Research Goal III: Infrastructure and Training Goal IV: Prevention and Control
    29. 29. Suggestions for Enhanced Public Health  Public health education  Continued collaborative efforts on the part of the international community  Government funding for biomedical and educational efforts  Recognition of infectious diseases that pose the greatest risk to public health  As usual, more research is needed...
    30. 30. Conclusions  Emerging infectious diseases are omnipotent and will continue to command attention. – EID’s are most deleterious in 1) developing nations and 2) among children, the elderly, females, and those with weakened immune systems  EID’s are controllable!  It is the responsibility of the global community to continue to develop / refine public health infrastructures to deal with burgeoning crises.  Initiatives must be developed in order to overcome social, religions, and regional barriers to prevention and control.
    31. 31. Useful Documents on the World Wide Web  Emerging Infectious Diseases – http://www.cdc.gov/ncidod/EID/index.htm  HIV/AIDS Education / Prevention Slide Set –http://www.cdc.gov/hiv/graphics.htm  Morbidity and Mortality Weekly Report (MMWR) –http://www2.cdc.gov/mmwr/  Preventing Emerging Infectious Diseases: A Strategy for the 21st Century –http://www.cdc.gov/ncidod/emergplan/p lan98.pdf
    32. 32. Useful Sites on the World Wide Web  Alliance for the Prudent Use of Antibiotics –http://www.healthsci.tufts.edu/apua/apu a.html  Centers for Disease Control and Prevention –http://www.cdc.gov  International Trachoma Institute –http://www.trachoma.org/  ProMed Email –http://www.promed.org/  World Health Organization –http://www.who.ch

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