EMERGING DISEASES: EMERGING DISEASES
IMPACT OF INFECTIOUS DISEASES : IMPACT OF INFECTIOUS DISEASES 14th Century - Europe - plague kills 20-45%
1831 - Cairo - 13% of population succumbs to cholera
1854-56 - Crimean war – deaths due to dysentery 10 times higher than deaths due to casualties
1899-1902 - Boer War – deaths due to dysentery 5 time higher than deaths due to casualties
Slide3: Los Angeles Times, 20 Sept 2007
Slide4: CNN, 4 Oct 2007
Slide5: Deadly Conjunctivitis Hits Mumbai
October 5, 2007
Slide6: 'Deadly' conjunctivitis hits Mumbai’ Madhavi Rajadhyaksha, TNN
Slide7: 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: 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).
MICROBIAL THREATS (1) : MICROBIAL THREATS (1) Newly recognized agents (SARS, acinetobacter)
Mutation of zoonotic agents that cause human disease (e.g., H5N1)
Resurgence of endemic diseases (malaria)
MICROBIAL THREATS (2) : MICROBIAL THREATS (2) Development of drug-resistant agents (tuberculosis, gonorrhea)
Recognition of etiologic role in chronic diseases (chlamydia causing respiratory and heart disease)
Use of infectious agents for terrorism and warfare (anthrax)
Slide16: National Academies Press
http://www.nap.edu/books/0309071844/html/13.html Multidrug resistant
Slide17: Preventing Emerging Infectious Diseases: A Strategy for the 21st century. The CDC Plan, p. 26, 1998.
Slide18: Enserink M. Old drugs losing effectiveness against flu; could statins fill gap? Science 309:177, 2005.
NEWLY IDENTIFIED INFECTIOUS DISEASES AND PATHOGENS (1): NEWLY IDENTIFIED INFECTIOUS DISEASES AND PATHOGENS (1) Year Disease or Pathogen
1993 Hantavirus pulmonary syndrome (Sin Nombre
virus)
1992 Vibrio cholerae O139
1991 Guanarito virus
1989 Hepatitis C
1988 Hepatitis E; human herpesvirus 6
1983 HIV
1982 Escherichia coli O157:H7; Lyme borreliosis;
human T-lymphotropic virus type 2
1980 Human T-lymphotropic virus Source: Workshop presentation by David Heymann, World Health Organization, 1999
NEWLY IDENTIFIED INFECTIOUS DISEASES AND PATHOGENS (2): NEWLY IDENTIFIED INFECTIOUS DISEASES AND PATHOGENS (2) Year Disease or Pathogen
2004 Avian influenza (human cases)
2003 SARS
1999 Nipah virus
1997 H5N1 (avian influenza A virus)
1996 New variant Creutzfelt-Jacob disease;
Australian bat lyssavirus
1995 Human herpesvirus 8 (Kaposi’s sarcoma
virus)
1994 Savia virus; Hendra virus Source: Workshop presentation by David Heymann, World Health Organization, 1999
DISEASE EMERGENCE AND RE-EMERGENCE: CAUSES: DISEASE EMERGENCE AND RE-EMERGENCE: CAUSES GENETIC/BIOLOGIC FACTORS
Host and agent mutations
Increased survival of susceptibles
HUMAN BEHAVIOR
POLITICAL
SOCIAL
ECONOMIC
PHYSICAL ENVIRONMENTAL FACTORS
ECOLOGIC FACTORS
Climatic changes
Deforestation
Etc.
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (1): FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (1)
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.
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (2): 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
Climate changes cause changes in geography of agents and vectors
Changing human behaviours, such as increased use of child-care facilities, sexual and drug use behaviours, and patterns of outdoor recreation
Social inequality
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (3): 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 transported great distances.
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (4): 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 of infectious agents such as Mycobacterium tuberculosis and Neisseria gonorrhoeae to chemoprophylactic or chemotherapeutic medicines.
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (5): 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 or new diseases that result in infectious diseases caused by agents not usually pathogenic in healthy hosts.(e.g. leukemia patients)
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (6): 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
Illiteracy limits knowledge of prevention strategies
Lack of political will – corruption, other priorities
FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (7): FACTORS CONTRIBUTING TO EMERGENCE OR RE-EMERGENCE OF INFECTIOUS DISEASES (7) Biowarfare/bioterrorism: An unfortunate 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.
STRATEGIES TO REDUCE THREATS (1): STRATEGIES TO REDUCE THREATS (1) IMPROVE GLOBAL RESPONSE CAPACITY
WHO
National Disease Control Units (e.g. USCDC, CCDC)
IMPROVE GLOBAL SURVEILLANCE
Improve diagnostic capacity (training, regulations)
Improve communication systems (web, e-mail etc.)
Rapid data analysis
Develop innovative surveillance and analysis strategies
Utilize geographical information systems
Utilize global positioning systems
Utilize the Global Atlas of Infectious Diseases (WHO)
STRATEGIES TO REDUCE THREATS (2): STRATEGIES TO REDUCE THREATS (2) USE OF VACCINES
Increase coverage and acceptability (e.g., oral)
Develop new strategies for delivery (e.g. oral and nasal administration)
Develop new vaccines
Decrease cost
NEW DRUG DEVELOPMENT
STRATEGIES TO REDUCE THREATS (3): STRATEGIES TO REDUCE THREATS (3) DECREASE INAPPROPRIATE DRUG USE
Improve education of clinicians
Decrease antimicrobial use in agriculture and food production
IMPROVE VECTOR AND ZOONOTIC CONTROL
Develop new insecticides
Develop more non-chemical strategies e.g. organic strategies
BETTER AND MORE WIDESPREAD HEALTH EDUCATION (e.g., west Nile virus; bed nets, mosquito repellent)
STRATEGIES TO REDUCE THREATS (4): STRATEGIES TO REDUCE THREATS (4) ESTABLISH PRIORITIES
The risk of disease
The magnitude of disease burden
Morbidity/disability
Mortality
Economic cost
REDUCE POTENTIAL FOR RAPID SPREAD
DEVELOP MORE FEASIBLE CONTROL STRATEGIES
STRATEGIES TO REDUCE THREATS (5): STRATEGIES TO REDUCE THREATS (5) Develop new strategies requiring low-cost technology
Social and political mobilization of effort
Greater support for research
Reduce poverty and inequality
ROLE OF THE PUBLIC HEALTH PHYSICIAN (1): ROLE OF THE PUBLIC HEALTH PHYSICIAN (1) Establish surveillance for:
Unusual diseases
Drug resistant agents
Assure laboratory capacity to investigate new agents
Develop plans for handling outbreaks of unknown agents
Inform physicians about responsible antimicrobial use
ROLE OF THE PUBLIC HEALTH PHYSICIAN (2): ROLE OF THE PUBLIC HEALTH PHYSICIAN (2) Educate public about
Responsible drug compliance
Emergence of new agents
Infection sources
Vector control
Malaria prophylaxis
Be aware of potential adverse effects of intervention strategies
Slide36: EPIDEMIOLOGY AND BIOLOGY OF INFLUENZA
Clinical Outcomes of Influenza Infection: Clinical Outcomes of Influenza Infection Asymptomatic
Symptomatic
Respiratory syndrome - mild to severe
Involvement of major organs - brain,
heart, etc.
Death
Factors Influencing the Response to Influenza: Factors Influencing the Response to Influenza Age
Pre-existing immunity (some crossover)
Smoking
Concurrent other health conditions
Immunosuppression
Pregnancy
Virology of Influenza: Virology of Influenza Subtypes:
A - Causes outbreak
B - Causes outbreaks
C - Does not cause outbreaks
Immunogenic Components of the Influenza Virus: 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 - H5N1
2004 avian influenza - H5N1
Antigenic mix determines severity of disease
Human response specific to hemagglutinin and neurominidase glycoproteins
Slide41: Figure 1. Natural hosts of influenza viruses Nicholson et al. Influenza. Lancet 362:1734, 2003
Genetic Changes in Influenza: Genetic Changes in Influenza Antigenic drift - results of errors in replication and lack of repair mechanism to correct errors
Antigenic shift - reassortment of genetic materials when concurrent infection of different strains occurs in the same host
Slide43: Nicholson et al. Influenza. Lancet 362:1735, 2003 Figure 2. Origin of antigenic shift and pandemic influenza. The segmented nature of the influenza A genome, which has eight genes, facilitates reassortment; up to 256 gene combinations are possible during coinfection with human and non-human viruses. Antigenic shift can arise when genes encoding at least the haemagglutinin surface glycoprotein are introduced into people, by direct transmission of an avian virus from birds, as occurred with H5N1 virus, or after genetic reassortment in pigs, which support the growth of both avian and human viruses.
Slide44: EPIDEMIOLOGY AND BIOLOGY OF AVIAN INFLUENZA
Characteristics of H5N1 Avian Influenza: 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%
Spread of H5N1 Avian Influenza: Spread of H5N1 Avian Influenza
12 14 16 18 20 22 24 26 28 30 1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 2
December, 2003 January Feb 2005-6 2006-7
2004 South Korea Vietnam Japan Thailand Cambodia China & Laos Indonesia Resurgence in Thailand, Vietnam, Cambodia and Indonesia Europe, Africa
Slide47: Outbreaks of Avian Influenza A (H5N1)... MMWR 53(5):102, 2004 Outbreaks of Avian Influenza A (H5N1)... MMWR 53(5):102, 2004
Intervention Strategies: Intervention Strategies Culling (killing of infected flocks)
Innovative surveillance strategies
- Identification and analysis of human to
human clusters
- Characterization of strains
- Necessary for vaccine development
(Science 304:968-9, 5/2004)
Vaccination of bird handlers (vaccine being developed)
Vaccination of commercial bird flocks
Barriers to H5N1 Control: 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