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Public Health 150 Contemporary Issues in Public Health. Emerging Infectious Diseases Robert Kim-Farley, MD, MPH.

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public health 150 contemporary issues in public health

Public Health 150Contemporary Issues in Public Health

Emerging Infectious Diseases

Robert Kim-Farley, MD, MPH

Emerging Infectious Diseases

slide2

Infectious disease is one of the few genuine adventures left in the world. The dragons are all dead and the lance grows rusty in the chimney corner . . . About the only sporting proposition that remains unimpaired by the relentless domestication of a once free-living human species is the war against those ferocious little fellow creatures, which lurk in the dark corners and stalk us in the bodies of rats, mice and all kinds of domestic animals; which fly and crawl with the insects, and waylay us in our food and drink and even in our love.

- (Hans Zinsser,1934 quoted in Murphy 1994)

Emerging Infectious Diseases

control and prevention programs
CONTROL AND PREVENTION PROGRAMS
  • Public heath planning for the control of infectious diseases must consider a number of factors to design optimal, rationally based control and prevention programs, including:
    • the risk of disease;
    • the magnitude of disease burden (as measured by mortality, degree of disability, morbidity, and economic costs);
    • the feasibility of control strategies;

Emerging Infectious Diseases

control and prevention programs continued
CONTROL AND PREVENTION PROGRAMS (continued)
  • the cost of control measures;
  • the effectiveness of such measures (on current levels of disease and impact on future cases or outbreaks);
  • the adverse effects or complications of the control measures; and
  • the availability of resources.

Emerging Infectious Diseases

risk and magnitude of diseases
Risk and Magnitude of Diseases
  • The tools of disease surveillance for recognition and evaluation of the patterns of disease can provide the information on the risk and magnitude of disease burden to individuals, persons in institutions, subgroups of populations, and the community at large.
  • Establishment and maintenance of the infrastructure for surveillance, including a system for the reporting of notifiable infectious diseases and unusual events, must be a high priority. Unusual events, like with SARS, may portend new and emerging diseases.

Emerging Infectious Diseases

feasibility of control
Feasibility of Control
  • Feasibility of possible control and prevention strategies must be assessed through operational research, pilot projects or from field experience.
    • The fact that a particular measure can help control a disease does not mean it can be applied on a sufficient scale to have the desired impact.

Emerging Infectious Diseases

cost of control
Cost of Control
  • The cost of control activities (in both manpower and materiel) can be assessed through costing studies.
    • A costly measure, even if it provides a high degree of control for an infectious disease, may not be affordable to the society or reasonable to apply in the light of other less expensive alternative strategies.

Emerging Infectious Diseases

effectiveness of control measures
Effectiveness of Control Measures
  • Effectiveness of control measures may be assessed through epidemiologic studies to find out their impact on reduction in the incidence or prevalence of disease.

Emerging Infectious Diseases

availability of resources
Availability of Resources
  • The availability of resources for preventive and control programs forces public health planners to set priorities by taking into account all these factors and then designing programs that have maximum impact within available resources.
  • Planners have a responsibility to mobilize additional necessary resources by raising public awareness and generating political will.

Emerging Infectious Diseases

availability of resources continued
Availability of Resources(continued)
  • Effective communication of disease burden and the results achievable through well-managed and effective control programs can be a powerful tool for advocacy.
  • Ideally, communities should actively participate in the planning, execution, and evaluation of public health programs.

Emerging Infectious Diseases

international migration
International Migration
  • The situation of international migration of many persons in the world today presents an additional complexity to the design of programs for the control of infectious diseases, especially emerging infectious diseases.
  • Pertinent issues include:
    • refugee camps,
    • legal status of migrants in recipient countries, and
    • temporary return migration.

Emerging Infectious Diseases

international commerce and transportation
International Commerce and Transportation
  • International commerce and transportation are specific areas of concern for public health infectious disease control programs and emerging diseases, especially as the speed of travel has increased.

Emerging Infectious Diseases

international commerce and transportation continued
International Commerce and Transportation (continued)
  • The tools of control include such measures as:
    • spraying insecticides effective against mosquito vectors of malaria in aircraft before departure, in transit, or on arrival; and
    • rat-proofing or periodic fumigation to control rats on ships, docks, and warehouses to prevent plague.

Emerging Infectious Diseases

international commerce and transportation continued14
International Commerce and Transportation (continued)
  • Specific international control measures relating to aircraft, ships, and land transportation for infectious diseases have been specified in the WHO International health regulations.

Emerging Infectious Diseases

emerging infectious diseases
EMERGING INFECTIOUS DISEASES

Microbes and vectors swim in the evolutionary stream, and they swim faster than we do. Bacteria reproduce every 30 minutes. For them, a millennium is compressed into a fortnight. They are fleet afoot, and the pace of our research must keep up with them, or they will overtake us. Microbes were here on earth 2 billion years before humans arrived, learning every trick for survival, and it is likely that they will be here 2 billion years after we depart (Krause 1998).

Emerging Infectious Diseases

factors contributing to emergence or re emergence of infectious diseases
Factors contributing to emergence or re-emergence of infectious diseases
  • 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.

Emerging Infectious Diseases

factors contributing to emergence or re emergence of infectious diseases continued
Factors contributing to emergence or re-emergence of infectious diseases (continued)
  • 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.

Emerging Infectious Diseases

factors contributing to emergence or re emergence of infectious diseases continued18
Factors contributing to emergence or re-emergence of infectious diseases (continued)
  • 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.

Emerging Infectious Diseases

factors contributing to emergence or re emergence of infectious diseases continued19
Factors contributing to emergence or re-emergence of infectious diseases (continued)
  • 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.

Emerging Infectious Diseases

factors contributing to emergence or re emergence of infectious diseases continued20
Factors contributing to emergence or re-emergence of infectious diseases (continued)
  • 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.

Emerging Infectious Diseases

factors contributing to emergence or re emergence of infectious diseases continued21
Factors contributing to emergence or re-emergence of infectious diseases (continued)
  • Deterioration in surveillance systems for infectious diseases, including laboratory support, to detect new or emerging disease problems at an early stage.
  • Antimicrobial drug resistance as a major factor in the emergence and re-emergence of infectious diseases deserves special attention.

Emerging Infectious Diseases

factors contributing to emergence or re emergence of infectious diseases continued22
Factors contributing to emergence or re-emergence of infectious diseases (continued)
  • Biowarfare/bioterrorism: An unfortunate potential source of a new or emerging disease threat.

Emerging Infectious Diseases

examples of emerging infectious disease threats
Examples of emerging infectious disease threats
  • 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.

Emerging Infectious Diseases

examples of emerging infectious disease threats continued
Examples of emerging infectious disease threats (continued)
  • 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.

Emerging Infectious Diseases

examples of emerging infectious disease threats continued25
Examples of emerging infectious disease threats (continued)
  • 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.

Emerging Infectious Diseases

examples of emerging infectious disease threats continued26
Examples of emerging infectious disease threats (continued)
  • 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.

Emerging Infectious Diseases

examples of emerging infectious disease threats continued27
Examples of emerging infectious disease threats (continued)
  • 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.

Emerging Infectious Diseases

examples of emerging infectious disease threats continued28
Examples of emerging infectious disease threats (continued)
  • 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.

Emerging Infectious Diseases

examples of emerging infectious disease threats continued29
Examples of emerging infectious disease threats (continued)
  • 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.

Emerging Infectious Diseases

examples of emerging infectious disease threats continued30
Examples of emerging infectious disease threats (continued)
  • 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 previous standard diagnostic tests are ineffective.

Emerging Infectious Diseases

examples of emerging infectious disease threats continued31
Examples of emerging infectious disease threats (continued)
  • SARS is the most recent example of how devastating a newly emerging disease can be in terms of economic impact and how, in the absence of vaccines, chemoprophylaxis, or chemotherapy “old” measures of quarantine and isolation may be the only “tools” we in public health have to combat disease.

Emerging Infectious Diseases

final thoughts
Final thoughts
  • It is only through worldwide concerted action will the effort to control infectious disease be effective (analogy).

Emerging Infectious Diseases

final thoughts continued
Final thoughts (continued)
  • We have now entered an era where, as Nobel Laureate Dr. Joshua Lederberg has stated, “The microbe that felled one child in a distant continent yesterday can reach yours today and seed a global pandemic tomorrow”

Emerging Infectious Diseases

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