1. EMERGING AND RE-EMERGING INFECTIOUS DISEASES
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2. Learning Objective
To able to define and give example of emerging and reemerging infectious disease (ERID).
Able to discuss what is the factors contributed to ERID
List current pathogens classified as ERID
Explain what steps is used to lower the threat of ERID
Have understanding of Influenza and dengue as ERID cases

3. IMPACT OF INFECTIOUS DISEASES
Emerging Infectious Diseases
IMPACT OF INFECTIOUS DISEASES
14th century - Europe - plague kills 20-45% of the
world’s population
Cairo - 13% of population succumbs to cholera
Crimean war – deaths due to
dysentery were 10 times higher than deaths due to casualties
Boer War – deaths due to dysentery were 5 times higher
than deaths due to casualties
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4. Emerging Infectious Diseases
Direct economic impact of selected infectious disease outbreaks,
Heymann DL. Emerging and re-emerging infections. In Oxford Textbook of Public Health, 5th ed, 2009, p1267.
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5. Emerging Infectious Diseases
Forum on Microbial Threats. The impact of globalization on infectious disease emergence and control. Institute of Medicine of the National Academies, Washington DC, 2006, p. 5.
Emerging Infectious Diseases
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6. Definition Emerging infectious disease (EID):
Infectious disease whose incidence has increased in the past 20 years and threatens to increase in the near future
Include
Newly recognized agents (SARS, acinetobacter)
Mutation of zoonotic agents that cause human disease (e.g., H5N1, H1N1)
Resurgence of endemic diseases (malaria, tuberculosis)

7. Re-emerging infectious disease:
re-emergence of microbes that had been successfully controlled.
E.g:
Dengue
Enterovirus 71
Clostridium difficile
Mumps virus
Streptococcus, Group A
Staphylococcus aureus

8. Emerging Infectious Diseases
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (1)
Human demographic change
Human move to new area and are exposed to new environmental sources of infectious agents, insects and animals
Unsustainable urbanization
causes breakdowns of sanitary and other public health measures in overcrowded cities (e.g., slums)
Multiple factors contribute to the emergence of new or re-emergence of previously known diseases (Lederberg et al. 1992; Centers for Disease Control and Prevention 1994; Murphy 1994), including the following:
- Human demographic change by which persons begin to live in previously uninhabited remote areas of the world and are exposed to new environmental sources of infectious agents, insects and animals.
- Breakdowns of sanitary and other public health measures in overcrowded cities and in situations of civil unrest and war.
- Economic development and changes in the use of land, including deforestation, reforestation, and urbanization.
- Other human behaviors, such as increased use of child-care facilities, sexual and drug use behaviors, and patterns of outdoor recreation.
- International travel and commerce that quickly transport people and goods vast distances.
- Changes in food processing and handling, including foods prepared from many different individual animals and transported great distances.
- Evolution of pathogenic infectious agents by which they may infect new hosts, produce toxins, or adapt by responding to changes in the host immunity.
- Development of resistance of infectious agents such as Mycobacterium tuberculosis and Neisseria gonorrhoeae to chemoprophylactic or chemotherapeutic medicines.
Resistance of the vectors of vector-borne infectious diseases to pesticides.
- Immunosuppression of persons due to medical treatments or new diseases that result in infectious diseases caused by agents not usually pathogenic in healthy hosts.
- Deterioration in surveillance systems for infectious diseases, including laboratory support, to detect new or emerging disease problems at an early stage.
Examples of emerging infectious disease threats include the following:
- Toxic shock syndrome, due to the infectious toxin-producing strains of Staphylococcus aureus, illustrates how a new technology yielding a new product, super-absorbent tampons, can create the circumstances favoring the emergence of a new infectious disease threat.
- Lyme disease, due to the infectious spirochete Borrelia burgdorferi, illustrates how changes in the ecology, including reforestation, increasing deer populations, and suburban migration of the population, can result in the emergence of a new microbial threat that has now become the most prevalent vector-borne disease in the United States.
- Shigellosis, giardiasis, and hepatitis A are examples of emerging diseases that have become threats to staff and children in child-care centers as the use of such centers has increased due to changes in the work patterns of societies.
- Opportunistic infections, such as pneumocystis pneumonia caused by Pneumocystis carinii, chronic cryptosporidiosis caused by Cryptosporidium species, and disseminated cytomegalovirus infections, illustrate emerging disease threats to the increasing number of persons who are immunosuppressed because of cancer chemotherapy, organ transplantation, or HIV infection.
- Foodborne infections such as diarrhea caused by the enterohemorrhagic strain 0157:H7 of Escherichia coli and waterborne infections such as gastrointestinal disease due to Cryptosporidium species are examples of emerging disease threats that have arisen due to such factors as changes in diet, food processing, globalization of the food supply and contamination of municipal water supplies.
Hantavirus pulmonary syndrome first detected in the USA in 1993 and caused by a previously unrecognized hantavirus illustrates how exposure to certain kinds of infected rodents can result in an emerging infectious disease.
Nipah virus disease first detected in Malaysia in 1999 and caused by a previously unrecognised Hendra-like virus demonstrates how close contact with pigs can result in an emerging infectious disease.
Emergence of the new toxigenic Vibrio cholerae O139 strain of cholera in Asia is an example of a new strain of an infectious agent for which there is no protection from prior infection with other strains or with current vaccines and for which standard diagnostic tests are ineffective.
Detels - 10 Oct 2011

9. Emerging Infectious Diseases
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (2)
Economic development and changes in the use of land
including deforestation, reforestation, and urbanization
Global warming
changes in geographical distribution of agents and vectors
Changing human behaviours
increased use of child-care facilities, sexual and drug use behaviours, and patterns of outdoor recreation
Social inequality
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10. Emerging Infectious Diseases
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (3)
International travel and commerce
that quickly transport people and goods vast distances
Changes in food processing and handling
including foods prepared from many different individual animals and countries, and transported great distances
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11. Emerging Infectious Diseases
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (4)
Evolution of pathogenic infectious agents
by which they may infect new hosts, produce toxins, or adapt by responding to changes in the host immunity.(e.g. influenza, HIV)
Development of resistance by infectious agents
such as Mycobacterium tuberculosis and Neisseria gonorrhoeae to chemoprophylactic or chemotherapeutic medicines.
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12. Emerging Infectious Diseases
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (5)
Resistance of the vectors of vector-borne infectious diseases to pesticides.
Immunosuppression of persons due to medical treatments
result in infectious diseases caused by agents not usually pathogenic in healthy hosts.(e.g. leukemia patients)
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13. Emerging Infectious Diseases
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (6)
Deterioration in surveillance systems for infectious diseases,
including laboratory support, to detect new or emerging disease problems at an early stage (e.g. Indonesian resistance to “scientific colonialism”)
Illiteracy limits knowledge and implementation of prevention strategies
Lack of political will – corruption, other priorities
Antimicrobial drug resistance as a major factor in the emergence and re-emergence of infectious diseases deserves special attention. Although significant reductions in infectious disease mortality have occurred since the introduction antimicrobials for general use in the 1940s, antimicrobial drug resistance has emerged because of their widespread use in humans.
Drugs that once seemed invincible are losing their effectiveness for a wide range of community-acquired infections, including tuberculosis, gonorrhea, pneumococcal infections (a leading cause of otitis media, pneumonia, and meningitis), and for hospital-acquired enterococcal and staphylococcal infections. Resistance to antiviral (e.g. amantadine-resistant influenza virus and acyclovir-resistant herpes simplex), anti-fungal (e.g. azole-resistant Candida species), and anti-protozoal (e.g., metronidazole-resistant Trichomonas vaginalis) drugs is also emerging. Drug-resistant malaria has spread to nearly all areas of the world where malaria occurs. Concern has also arisen over strains of HIV resistant to antiviral drugs. Increased microbial resistance has resulted in prolonged hospitalizations and higher death rates from infections; has required much more expensive, and often more toxic, drugs or drug combinations (even for common infections); and has resulted in higher health care costs (Centers for Disease Control and Prevention 1994).
Antimicrobial drug resistance has also emerged because of the use of antimicrobials in domesticated animals. For example, the use of fluoroquinolones in poultry has created a reservoir of quinolone-resistant Campylobacter jejuni that has now been isolated in humans.
An aggressive public health response to these new, emerging and re-emerging infectious disease threats must be made to characterize them better and to mount an effective response for their control. For example, the 1999 outbreak of West Nile fever in New York City and surrounding areas demonstrates how a viral encephalitis, initially classified as St. Louis encephalitis and later confirmed to be due to West Nile-like virus, can reach far beyond its normal setting.
The WHO (WHO 1995a) has outlined the following high priority areas: (a) strengthen global surveillance of infectious diseases; (b) establish national and international infrastructures to recognize, report and respond to new disease threats; (c) further develop applied research on diagnosis, epidemiology, and control of emerging infectious diseases; and (d) strengthen the international capacity for infectious disease prevention and control.
Another unfortunate source of a new or emerging disease threat is the spectre of biological warfare or bioterrorism, especially in an age where terrorist acts are frequent events (Christopher et al, 1997). Several countries are developing rapid response capability to deal with such contingencies.
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14. Emerging Infectious Diseases
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (7)
Biowarfare/bioterrorism:
potential source of new or emerging disease threats (e.g. anthrax and letters)
War, civil unrest
creates refugees, food and housing shortages, increased density of living, etc.
Famine causing reduced immune capacity, etc.
Manufacturing strategies;
e.g., pooling of plasma, etc.
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15. NEWLY IDENTIFIED INFECTIOUS DISEASES AND PATHOGENS (1)
Emerging Infectious Diseases
NEWLY IDENTIFIED INFECTIOUS DISEASES AND PATHOGENS (1)
Year Disease or Pathogen
Hantavirus pulmonary syndrome (Sin Nombre
virus)
Vibrio cholerae O139
Guanarito virus
Hepatitis C
Hepatitis E; human herpesvirus 6
HIV
Escherichia coli O157:H7; Lyme borreliosis;
human T-lymphotropic virus type 2
Human T-lymphotropic virus
Source: Workshop presentation by David Heymann, World Health Organization, 1999
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16. NEWLY IDENTIFIED INFECTIOUS DISEASES AND PATHOGENS (2)
Emerging Infectious Diseases
NEWLY IDENTIFIED INFECTIOUS DISEASES AND PATHOGENS (2)
Year Disease or Pathogen
H1N1
Avian influenza (human cases)
SARS
Nipah virus
H5N1 (avian influenza A virus)
New variant Creutzfelt-Jacob disease;
Australian bat lyssavirus
Human herpesvirus 8 (Kaposi’s sarcoma
virus)
Savia virus; Hendra virus
Source: Workshop presentation by David Heymann, World Health Organization, 1999
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17. STRATEGIES TO REDUCE THREATS (1)
Emerging Infectious Diseases
STRATEGIES TO REDUCE THREATS (1)
DEVELOP POLITICAL WILL AND FUNDING
IMPROVE GLOBAL EARLY RESPONSE CAPACITY
WHO
National Disease Control Units (e.g. USCDC, CCDC)
Training programs
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18. STRATEGIES TO REDUCE THREATS (2)
Emerging Infectious Diseases
IMPROVE GLOBAL SURVEILLANCE
Improve diagnostic capacity (training, regulations)
Improve communication systems (web, etc.) and sharing of surveillance data
Rapid data analysis
Develop innovative surveillance and analysis strategies
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19. STRATEGIES TO REDUCE THREATS (3)
Emerging Infectious Diseases
3. IMPROVE GLOBAL SURVEILLANCE (continued)
Utilize geographical information systems
Utilize global positioning systems
Utilize the Global Atlas of Infectious Diseases (WHO)
Increase and improve laboratory capacity
Coordinate human and animal surveillance
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20. Emerging Infectious Diseases
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21. STRATEGIES TO REDUCE THREATS (4)
Emerging Infectious Diseases
STRATEGIES TO REDUCE THREATS (4)
4. USE OF VACCINES
Increase coverage and acceptability (e.g., oral)
New strategies for delivery (e.g., nasal spray administration)
Develop new vaccines
Decrease cost
Decrease dependency on “cold chain”
5. NEW DRUG DEVELOPMENT
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22. STRATEGIES TO REDUCE THREATS (5)
Emerging Infectious Diseases
STRATEGIES TO REDUCE THREATS (5)
6. DECREASE INAPPROPRIATE DRUG USE
Improve education of clinicians and public
Decrease antimicrobial use in agriculture and food production
7. IMPROVE VECTOR AND ZOONOTIC CONTROL
Develop new safe insecticides
Develop more non-chemical strategies e.g. organic strategies
8. BETTER AND MORE WIDESPREAD HEALTH EDUCATION (e.g., west Nile virus; bed nets, mosquito repellent)
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23. STRATEGIES TO REDUCE THREATS (5)
Emerging Infectious Diseases
STRATEGIES TO REDUCE THREATS (5)
9. Develop new strategies requiring low-cost technology
10. Social and political mobilization of communities
11. Greater support for research
12. Reduce poverty and inequality
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24. Emerging Infectious Diseases
EPIDEMIOLOGY AND BIOLOGY OF INFLUENZA
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25. Clinical Outcomes of Influenza Infection
Emerging Infectious Diseases
Clinical Outcomes of Influenza Infection
Asymptomatic
Symptomatic
Respiratory syndrome - mild to severe
Gastrointestinal symptoms
Involvement of major organs - brain, heart, etc.
Death
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26. Emerging Infectious Diseases
Virology of Influenza
Subtypes:
A - Causes outbreak
B - Causes outbreaks
C - Does not cause outbreaks
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27. Immunogenic Components of the Influenza Virus
Emerging Infectious Diseases
Immunogenic Components of the Influenza Virus
Surface glycoproteins, 15 hemagglutinin (H1-H15), nine neurominidases (N1-N9)
H1-H3 and N1N2 established in humans
Influenza characterized by combination of H and N glycoproteins
1917 pandemic - H1N1
2004 avian influenza - H5N1
2009 H1N1
Antigenic mix determines severity of disease
Human response specific to hemagglutinin and neurominidase glycoproteins
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28. Emerging Infectious Diseases
Figure 1. Natural hosts of influenza viruses
Nicholson et al. Influenza. Lancet 362:1734, 2003
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29. Emerging Infectious Diseases
The H1N1 Epidemic
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30. Emerging Infectious Diseases
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31. Emerging Infectious Diseases
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32. Factors Influencing the Response to Influenza
Emerging Infectious Diseases
Factors Influencing the Response to Influenza
Age
Pre-existing immunity (some crossover)
Smoking
Concurrent other health conditions
Immunosuppression
Pregnancy
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33. Emerging Infectious Diseases
Kaplan K. How the new virus came to be. LA Times, 14 Sept, 2009; latimes.com/health
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34. Emerging Infectious Diseases
EPIDEMIOLOGY AND BIOLOGY OF H5N1 INFLUENZA
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35. Characteristics of H5N1 Avian Influenza
Emerging Infectious Diseases
Characteristics of H5N1 Avian Influenza
1. Highly infectious and pathogenic for domestic poultry
2. Wild fowl, ducks asymptomatic reservoir
3. Now endemic in poultry in Southeast Asia
4. Proportion of humans with subclinical infection unknown
5. Case fatality in humans is >50%
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36. Spread of H5N1 Avian Influenza
Emerging Infectious Diseases
Spread of H5N1 Avian Influenza
December, January Feb
2004
South Korea
China & Laos
Resurgence in Thailand, Vietnam, Cambodia and Indonesia
Cambodia
Indonesia
Thailand
Vietnam
Europe, Africa
Japan
Detels - 10 Oct 2011

37. Intervention Strategies (H5N1)
Emerging Infectious Diseases
Intervention Strategies (H5N1)
Culling (killing of infected flocks)
Innovative surveillance strategies
- Identification and analysis of human to
human clusters
- Characterization of strains
* Necessity for vaccine development
(Science 304:968-9, 5/2004)
Vaccination of bird handlers (vaccine being developed)
Vaccination of commercial bird flocks
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38. Emerging Infectious Diseases
Barriers to H5N1 Control
Reservoir in wild birds and ducks
Economic impact of culling of poultry stocks
Popularity of “wet markets” promotes transmission within poultry and to other species (e.g., pigs)
Resistance to antivirals and vaccines
Mistrust of rich nations
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39. Emerging Infectious Diseases
Don’t get the flu vaccine!
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40. Emerging Infectious Diseases
RECOMMENDATIONS TO PREVENT FLU
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41. STRATEGIES TO PREVENT FLU (1)
Emerging Infectious Diseases
STRATEGIES TO PREVENT FLU (1)
COVER MOUTH AND NOSE WHEN SNEEZING
WASH HANDS FREQUENTLY WITH SOAP AND WATER OR ALCOHOL
AVOID TOUCHING EYES, NOSE AND MOUTH
AVOID CONTACT WITH SICK PEOPLE
AVOID CROWDED CONGESTED ENVIRONMENTS
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