15 October 2003 Emerging Infectious Diseases 1 Public Health 150 Contemporary Issues in Public Health Emerging Infectious Diseases Robert Kim-Farley, MD,

15 October 200315 October 2003 Emerging Infectious DiseasesEmerging Infectious Diseases 11

Public Health 150Public Health 150Contemporary Issues in Public Contemporary Issues in Public

HealthHealth

Emerging Infectious Emerging Infectious DiseasesDiseases

Robert Kim-Farley, MD, Robert Kim-Farley, MD, MPHMPH


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)


CONTROL AND PREVENTION CONTROL AND PREVENTION PROGRAMSPROGRAMS

Public heath planning for the control of Public heath planning for the control of infectious diseases must consider a infectious diseases must consider a number of factors to design optimal, number of factors to design optimal, rationally based control and prevention rationally based control and prevention programs, including:programs, including: the risk of disease; the risk of disease; the magnitude of disease burden (as the magnitude of disease burden (as

measured by mortality, degree of measured by mortality, degree of disability, morbidity, and economic disability, morbidity, and economic costs); costs);

the feasibility of control strategies; the feasibility of control strategies;


CONTROL AND PREVENTION CONTROL AND PREVENTION PROGRAMS (continued)PROGRAMS (continued)

the cost of control measures; the cost of control measures; the effectiveness of such measures (on the effectiveness of such measures (on

current levels of disease and impact on current levels of disease and impact on future cases or outbreaks); future cases or outbreaks);

the adverse effects or complications of the adverse effects or complications of the control measures; and the control measures; and

the availability of resources.the availability of resources.


Risk and Magnitude of Risk and Magnitude of DiseasesDiseases

The tools of disease surveillance for recognition and The tools of disease surveillance for recognition and evaluation of the patterns of disease can provide the evaluation of the patterns of disease can provide the information on the risk and magnitude of disease information on the risk and magnitude of disease burden to individuals, persons in institutions, burden to individuals, persons in institutions, subgroups of populations, and the community at subgroups of populations, and the community at large. large.

Establishment and maintenance of the infrastructure Establishment and maintenance of the infrastructure for surveillance, including a system for the reporting for surveillance, including a system for the reporting of notifiable infectious diseases and unusual events, of notifiable infectious diseases and unusual events, must be a high priority. Unusual events, like with must be a high priority. Unusual events, like with SARS, may portend new and emerging diseases.SARS, may portend new and emerging diseases.


Feasibility of ControlFeasibility of Control

Feasibility of possible control and Feasibility of possible control and prevention strategies must be prevention strategies must be assessed through operational assessed through operational research, pilot projects or from field research, pilot projects or from field experience. experience. The fact that a particular measure can The fact that a particular measure can

help control a disease does not mean it help control a disease does not mean it can be applied on a sufficient scale to can be applied on a sufficient scale to have the desired impact. have the desired impact.


Cost of ControlCost of Control

The cost of control activities (in both The cost of control activities (in both manpower and materiel) can be manpower and materiel) can be assessed through costing studies. assessed through costing studies. A costly measure, even if it provides a A costly measure, even if it provides a

high degree of control for an infectious high degree of control for an infectious disease, may not be affordable to the disease, may not be affordable to the society or reasonable to apply in the society or reasonable to apply in the light of other less expensive alternative light of other less expensive alternative strategies.strategies.


Effectiveness of Control Effectiveness of Control MeasuresMeasures

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


Availability of ResourcesAvailability of Resources

The availability of resources for preventive and The availability of resources for preventive and control programs forces public health planners control programs forces public health planners to set priorities by taking into account all these to set priorities by taking into account all these factors and then designing programs that have factors and then designing programs that have maximum impact within available resources. maximum impact within available resources.

Planners have a responsibility to mobilize Planners have a responsibility to mobilize additional necessary resources by raising additional necessary resources by raising public awareness and generating political will. public awareness and generating political will.


Availability of ResourcesAvailability of Resources(continued)(continued)

Effective communication of disease Effective communication of disease burden and the results achievable burden and the results achievable through well-managed and effective through well-managed and effective control programs can be a powerful tool control programs can be a powerful tool for advocacy. for advocacy.

Ideally, communities should actively Ideally, communities should actively participate in the planning, execution, participate in the planning, execution, and evaluation of public health programs.and evaluation of public health programs.


International MigrationInternational Migration

The situation of The situation of international migrationinternational migration of many persons in the world today presents of many persons in the world today presents an additional complexity to the design of an additional complexity to the design of programs for the control of infectious programs for the control of infectious diseases, especially emerging infectious diseases, especially emerging infectious diseases. diseases.

Pertinent issues include:Pertinent issues include: refugee camps, refugee camps, legal status of migrants in recipient countries, legal status of migrants in recipient countries,

and and temporary return migration. temporary return migration.


International Commerce and International Commerce and TransportationTransportation

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


International Commerce and International Commerce and Transportation (continued)Transportation (continued)

The tools of control include such The tools of control include such measures as: measures as: spraying insecticides effective against spraying insecticides effective against

mosquito vectors of malaria in aircraft mosquito vectors of malaria in aircraft before departure, in transit, or on arrival; before departure, in transit, or on arrival; and and

rat-proofing or periodic fumigation to rat-proofing or periodic fumigation to control rats on ships, docks, and control rats on ships, docks, and warehouses to prevent plague. warehouses to prevent plague.


International Commerce and International Commerce and Transportation (continued)Transportation (continued)

Specific international control Specific international control measures relating to aircraft, ships, measures relating to aircraft, ships, and land transportation for infectious and land transportation for infectious diseases have been specified in the diseases have been specified in the WHO WHO International health International health regulationsregulations..


EMERGING INFECTIOUS EMERGING INFECTIOUS DISEASESDISEASES

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


Factors contributing to emergence Factors contributing to emergence or re-emergence of infectious or re-emergence of infectious

diseasesdiseases

Human Human demographic changedemographic change by which by which persons begin to live in previously persons begin to live in previously uninhabited remote areas of the world and uninhabited remote areas of the world and are exposed to new environmental sources are exposed to new environmental sources of infectious agents, insects and animals. of infectious agents, insects and animals.

Breakdowns of sanitary and other Breakdowns of sanitary and other public health measurespublic health measures in overcrowded in overcrowded cities and in situations of civil unrest and cities and in situations of civil unrest and war.war.



diseases (continued)diseases (continued) Economic development and changes Economic development and changes

in the use of landin the use of land, including , including deforestation, reforestation, and deforestation, reforestation, and urbanization.urbanization.

OtherOther human behaviors human behaviors, such as , such as increased use of child-care facilities, increased use of child-care facilities, sexual and drug use behaviors, and sexual and drug use behaviors, and patterns of outdoor recreation.patterns of outdoor recreation.



diseases (continued)diseases (continued) International travel and International travel and

commercecommerce that quickly transport that quickly transport people and goods vast distances.people and goods vast distances.

Changes in food processing and Changes in food processing and handlinghandling, including foods prepared , including foods prepared from many different individual from many different individual animals and transported great animals and transported great distances.distances.



diseases (continued)diseases (continued) Evolution of pathogenic infectious agentsEvolution of pathogenic infectious agents

by which they may infect new hosts, produce by which they may infect new hosts, produce toxins, or adapt by responding to changes in toxins, or adapt by responding to changes in the host immunity.the host immunity.

Development of resistance of infectious Development of resistance of infectious agentsagents such as such as Mycobacterium tuberculosisMycobacterium tuberculosis and and Neisseria gonorrhoeaeNeisseria gonorrhoeae to to chemoprophylactic or chemotherapeutic chemoprophylactic or chemotherapeutic medicines.medicines.



diseases (continued)diseases (continued) Resistance of the vectorsResistance of the vectors of of

vector-borne infectious diseases to vector-borne infectious diseases to pesticides.pesticides.

Immunosuppression of personsImmunosuppression of persons due to medical treatments or new due to medical treatments or new diseases that result in infectious diseases that result in infectious diseases caused by agents not diseases caused by agents not usually pathogenic in healthy hosts.usually pathogenic in healthy hosts.



diseases (continued)diseases (continued) Deterioration in surveillance systemsDeterioration in surveillance systems

for infectious diseases, including laboratory for infectious diseases, including laboratory support, to detect new or emerging support, to detect new or emerging disease problems at an early stage.disease problems at an early stage.

Antimicrobial drug resistance Antimicrobial drug resistance as a as a major factor in the emergence and re-major factor in the emergence and re-emergence of infectious diseases deserves emergence of infectious diseases deserves special attention. special attention.



diseases (continued)diseases (continued) Biowarfare/bioterrorism: Biowarfare/bioterrorism: An An

unfortunate potential source of a unfortunate potential source of a new or emerging disease threat.new or emerging disease threat.


Examples of emerging Examples of emerging infectious disease threatsinfectious disease threats

Toxic shock syndrome, due to the Toxic shock syndrome, due to the infectious toxin-producing strains of infectious toxin-producing strains of Staphylococcus aureus,Staphylococcus aureus, illustrates how a illustrates how a new technology yielding a new product, new technology yielding a new product, super-absorbent tampons, can create super-absorbent tampons, can create the circumstances favoring the the circumstances favoring the emergence of a new infectious disease emergence of a new infectious disease threat.threat.


Examples of emerging Examples of emerging infectious disease threats infectious disease threats

(continued)(continued) Lyme disease, due to the infectious Lyme disease, due to the infectious

spirochete spirochete Borrelia burgdorferiBorrelia burgdorferi, , illustrates how changes in the ecology, illustrates how changes in the ecology, including reforestation, increasing deer including reforestation, increasing deer populations, and suburban migration of populations, and suburban migration of the population, can result in the the population, can result in the emergence of a new microbial threat emergence of a new microbial threat that has now become the most prevalent that has now become the most prevalent vector-borne disease in the United vector-borne disease in the United States.States.



(continued)(continued) Shigellosis, giardiasis, and hepatitis A Shigellosis, giardiasis, and hepatitis A

are examples of emerging diseases are examples of emerging diseases that have become threats to staff that have become threats to staff and children in child-care centers as and children in child-care centers as the use of such centers has the use of such centers has increased due to changes in the work increased due to changes in the work patterns of societies.patterns of societies.



(continued)(continued) Opportunistic infections, such as Opportunistic infections, such as

pneumocystis pneumonia caused by pneumocystis pneumonia caused by Pneumocystis carinii, Pneumocystis carinii, chronic chronic cryptosporidiosis caused by cryptosporidiosis caused by CryptosporidiumCryptosporidium species, and disseminated cytomegalovirus species, and disseminated cytomegalovirus infections, illustrate emerging disease threats infections, illustrate emerging disease threats to the increasing number of persons who are to the increasing number of persons who are immunosuppressed because of cancer immunosuppressed because of cancer chemotherapy, organ transplantation, or HIV chemotherapy, organ transplantation, or HIV infection.infection.



(continued)(continued) Foodborne infections such as diarrhea caused Foodborne infections such as diarrhea caused

by the enterohemorrhagic strain 0157:H7 of by the enterohemorrhagic strain 0157:H7 of Escherichia coliEscherichia coli and waterborne infections and waterborne infections such as gastrointestinal disease due to such as gastrointestinal disease due to CryptosporidiumCryptosporidium species are examples of species are examples of emerging disease threats that have arisen emerging disease threats that have arisen due to such factors as changes in diet, food due to such factors as changes in diet, food processing, globalization of the food supply processing, globalization of the food supply and contamination of municipal water and contamination of municipal water supplies.supplies.



(continued)(continued) Hantavirus pulmonary syndrome first Hantavirus pulmonary syndrome first

detected in the USA in 1993 and detected in the USA in 1993 and caused by a previously unrecognized caused by a previously unrecognized hantavirus illustrates how exposure hantavirus illustrates how exposure to certain kinds of infected rodents to certain kinds of infected rodents can result in an emerging infectious can result in an emerging infectious disease.disease.



(continued)(continued) Nipah virus disease first detected in Nipah virus disease first detected in

Malaysia in 1999 and caused by a Malaysia in 1999 and caused by a previously unrecognised Hendra-like previously unrecognised Hendra-like virus demonstrates how close virus demonstrates how close contact with pigs can result in an contact with pigs can result in an emerging infectious disease. emerging infectious disease.



(continued)(continued) Emergence of the new toxigenic Emergence of the new toxigenic Vibrio Vibrio

choleraecholerae O139 strain of cholera in Asia O139 strain of cholera in Asia is an example of a new strain of an is an example of a new strain of an infectious agent for which there is no infectious agent for which there is no protection from prior infection with protection from prior infection with other strains or with current vaccines other strains or with current vaccines and for which previous standard and for which previous standard diagnostic tests are ineffective.diagnostic tests are ineffective.



(continued)(continued) SARS is the most recent example of SARS is the most recent example of

how devastating a newly emerging how devastating a newly emerging disease can be in terms of economic disease can be in terms of economic impact and how, in the absence of impact and how, in the absence of vaccines, chemoprophylaxis, or vaccines, chemoprophylaxis, or chemotherapy “old” measures of chemotherapy “old” measures of quarantine and isolation may be the quarantine and isolation may be the only “tools” we in public health have to only “tools” we in public health have to combat disease.combat disease.


Final thoughtsFinal thoughts

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


Final thoughts (continued)Final thoughts (continued)

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

Documents

15 October 2003 Emerging Infectious Diseases 1 Public Health 150 Contemporary Issues in Public Health Emerging Infectious Diseases Robert Kim-Farley, MD,