??????? Infectious Disease Epidemiology

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??????? Infectious Disease Epidemiology
?????????????? Department of epidemiology
,Harbin Medical University
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? ? ? ? Teaching Content

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• study importance
• epidemic trends
• basic principles and
• methods
• infectious focus
• prevention control

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????????Study Importance

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• ????,????
• ????
• ?????????
• ????????

• Seriously burden of diseases
• Neglect of prevention ,the
• consequences of heavy
• The resurgence of relapse
• The new emerging infectious
• diseases
• Threat of bioterrorism

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1998???????
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• ???????(emerging infections or emerging
  infectious diseases,EID)??????????????????????????
  ?????????
• --- David Heymann 1997
• emerging infections refers to newly identified
  and previously unknown infectious diseases which
  cause public health problems,either locally or
  internationally?

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• ????????(re-emerging infectious
  diseases)???????????,?????????????????????????????
  ??????????????
• Re-emerging infectious diseases are infections
  that have been known about for some time but had
  fallen to such low levels that they were no
  longer considered a public health problem?They
  often reappear in epidemic proportions.

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?????????????? ??????? The characteristic
of EID

• ????
• Silent beginning
• ?????
• Globalization
• ?????
• Jump of infectious agent across the species
  barrier from animal to human being
• ?????????????????/????
• More virulent and/or epidemic

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EID?????The cause of EID

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• The change of population and people's behavior
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• Technological progress and industrialization

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EID?????The cause of EID

• ??????????????
• Economic development and land-use patterns
  change
• ???????????????????????
• The development of International travel, and
  commerce, and population movement

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EID?????The cause of EID

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• Pathogens variation
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  ??,????
• Lack of health resources

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???EID??????? Other causes of EID

• ????????,???????????????,????????????,????????????
  ?????????????????????????
• The global climate continues to warm
• ???????????
• Bioterrorism

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???????19671997????
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The epidemic trends of Infectious disease

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????????????
Major achievements of infectious diseases
prevention and control till 1970s

• Total morbidity decreased
• Total mortality decreased
• Fatality rate of the majority
• decreased
• Modes of Transmission changed
• Large scale epidemics decreased

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• ???????
• ???????????
• ????????????
• ???????

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Global burden of disease(DALY)(2000)
2000??????????(DALY)
DALY Disability adjusted life-year
Non communicable
Injury
communicable Malnutrition Etc.
Africa
Europe
America
E-S Asia
East-Med
West Pacific
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1950-2003????????????
Reporting data of legal infectious disease in
China (1950-2003)
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??????????
Leading infectious killers
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????????(2000)
Distribution of Tuberculosis Worldwide(2000)
100-250/per 100 000
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?????????(2000)
Distribution of C Hepatitis Worldwide(2000)
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????????? (2005)
The HIV epidemic in the Worldwide (2005)
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??????????
The Morbidity of Main Infectious Diseases in China
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19852001??????STD???
The Reported STD Cases in China
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1955-2003?????????
The Morbidity of Lupomania in China
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??????????????
The basic principles and methods of infectious
disease epidemiology

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(?)???Source of Infection

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• ??
• ?? cases
• ????? carriers
• ?????? animals

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• 1??? (cases)
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• In vivo existence massive pathogen
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• Clinical symptoms are advantageous for the
  pathogen discharges

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• ???(Incubation period)
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• The time interval between invasion by an
  infectious agent and appearance of the first
  signor symptom of the disease in question

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• ??????
• Significance of Incubation Period

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• To Determine The Infected Time
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• Tracing Sources Of Infection
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• To Identified The Route Of Transmission
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• To Determine The Quarantine And Medical
  Observation Period

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• ??????
• Significance of Incubation Period

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• To Determine The Time Of Immunization
• ????????
• Evaluation Of Effectiveness Of Preventive
  Measures
• ????????????? Can Affect The Epidemic
  Characteristics

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• 2??????(carrier)
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• A person or animal that harbors a specific
  infectious agent in the absence of discernible
  clinical disease and serves as a potential source
  of infection

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• 3???????(infectious animal)
• ???????(natural focal disease)
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• ??????????????
• ??????? ????

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• ?????????????????????????,???????????????????????
  ????????

• Transmission of infectious agent from animal to
  
• human called ZOONOSES

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?? crow
??? puma
?????????
Animals can transmit West Nile fever
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?----???
??-----??
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(?)???? Route of Transmission

• ??????????,?????????,??????????????

• The whole process that the pathogens experienced
  in the outer environment when they passed from
  an infected individual or group to a previously
  uninfected individual or group.

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????????
Modes of Infectious Disease Transmission

• Air-borne transmission
• Water-borne transmission
• Food-borne transmission
• Contact-transmitted diseases
• Vector-borne diseases
• Soil-transmitted diseases
• Nosocomial infection
• Vertical transmission

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• 1????????(Air-borne diseases)
• ???????,?????
• Transmission easy to comply, easy to outbreak
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• Mostly occurs in winter and spring
• ??????
• Mostly occurs in Children
• ????????????
• A cycle period in non-immunity population
• ?????????????
• Overcrowded live conditions and high population
  density

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• 2-1??????(Drinking Water Pollution)
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• Distribution Of Cases Consistent With The
  Water Supply Coverage
• ??????,????????
• Except To Lactated Infants, All Population Can
  Be

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• 2-1??????(Drinking Water Pollution)
• ??????,??????????
• If Often Contaminated, Can Be Expressed As
  Chronic Epidemic
• ????????,???????
• A Serious Pollution Can Cause An Outbreak
• ????????,????????
• Stop Drink Or Purified Water, Can Quell The
  Outbreak Or Epidemic

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• 2-2????? (Exposure to infected water)
• ?????
• History of exposure to infected water
• ????????????
• There are regional, seasonal and occupational
  characteristics
• ???????????
• More common in people who contact with
  infected water
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• A large number of susceptible who contact
  with infected water easy occur outbreaks
• ????????????
• Taken against measures can be controlled

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• 3??????(Food-borne Diseases)
• ????????,??????
• Involved Are Limited To Those Who Eat
  Contaminated Food
• ???????,?????
• A Large Number Of Contamination, The Outbreak
  Can Be Occur
• ????????,??????
• To Stop Supplying The Contaminated Food , The
  Outbreak Can Be Stop
• ?????
• The Incubation Period Is Shorter

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1988?????????????
???1988?13?????????
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• 4??????
• Contact-transmitted diseases
• ??
• ???? Direct contact    
• ?????????,????????????
• ???? Indirect contact
• ??????????????????????????????

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• 5???????? (Vector-borne diseases)
• ??
• ??? Regional ????
• ??? Occupational ????
• ??? Seasonal ??
• ????? More Young adults ???????

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• 6??????(Nosocomial infection)
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Nosocomial infections (pronounced,
nos-uh-KOH-mee-uhl), are infections which are a
result of treatment in a hospital or a healthcare
service unit.
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• 7??????(Vertical transmisssion)
• ??
• ???????????????,????????????
• ??
• ????? By placenta
• ????? By genital
• ????? By labour

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HIV????? ?? 15--25 ?????? 30 HIV???????(??)
????? 6.8 ?????????? 1.6
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(?)????? Herd Susceptibility

• ??????????????????
• The susceptibility degree of population, as a
  whole, to infectious diseases

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• ????? (The Increase Factors)
• ?????
• Increased Neonatal
• ??????
• Susceptible Population Move In
• ???????????
• Mmuno-population Immunity To Natural Healing
• ??????
• Immuno-population Has Been Dead

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• ????? (Reduction Factor)
• ???? EPI
• ????? Epidemics
• ???? Subclinical infection

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(?)??? Infectious focus

• 1??? (concept)
• ??????,????????????????????

The range that the sources of infection
spread pathogens around can reach to under
certain conditions.
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• 2?????
• (the formation conditions)
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• The source of infection exists
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• Pathogens can continue to spread

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• 3????? (eliminate conditions)
• ??????????????
• The source of infection has been removed or
  eliminate the carrier state
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• Carried out terminal disinfection
• ???????,????????????
• After the longest incubation period, no new
  infections occur among susceptible

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(?)?????????The factors that affect the epidemic
process

• 1?????(Natural factors)
• ?? (Climate)
• ???? (Geography)
• ?????????????????
• (Vector insects and host)

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• 2?????(Social factors)
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• The rapid development of global travel
• ?????????????
• Ecological deterioration caused by
  environmental pollution and destruction

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• 2?????(Social factors)
• ??????????
• The abuse of antibiotics and pesticides
• ????????
• Urbanization and population explosion
• ????????????
• War, riots, refugee flows and famine

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?????????Prevention and control of infectious
diseases

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Public Health Measures for Control of Epidemics
Involves strategies which break the "chain of
transmission"

• Immunization of people
• boosters frequently required
• 100 immunization is not necessary (herd
  immunity)
• Blocking vehicle-mediated transmission
• water purification
• effective cooking
• prevention of food contamination with infectious
  agents

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• Quarantine
• limiting freedom of movement of individuals
  carrying infectious agents
• minimum time required for a quarantine period is
  equal to longest period of communicability
  (transmissibility) of the disease
• Elimination of animal reservoirs
• immunization of animals that act as reservoirs of
  diseases such as bovine tuberculosis, brucellosis
  (highly effective when monitored properly)
• eradication of animals that act as reservoirs of
  diseases such as tularemia, plague, Lyme disease
  (sometimes effective, difficult to monitor
  properly) 

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Prevention, Intervention, Control, and
Eradication of Diseases

• Prevention
• implies the planning for and taking action to
  prevent or forestall the occurrence of an
  undesirable event and is therefore more desirable
  than . . .
• Intervention
• which is defined as taking of action during an
  event
• Control
• general term used in the containment of disease
• Eradication
• total elimination of the disease

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Control of Infectious diseases
HUMAN 1. Change behavior 2. Health education 3.
Vaccination ENVIRONMENT 1. Habitat
improvement 2. Water (or soil) treatment 3.
Revise agriculture pattern
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Control of Infectious diseases
RESERVOIRS 1. Treatment 2. Vaccination 3.
Eradication VECTORS 1. Chemical control 2.
Non-chemical control
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• ???????
• Communicable disease surveillance
• ?????
• Report infectious diseases

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• ????????
• The control measures for the source of infection
• (1)?? Cases
• ??? Early detection
• ??? Early diagnosis
• ??? Early reporting
• ??? Early isolation
• ??? Early treatment

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• ????? Carriers
• ?? Measures
• ?? Registration
• ?? Management
• ?? Follow up
• ?? Time limit

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• ??? Contacts
• ?? Quarantine
• ??(????) Isolated observation
• ???? Medical observation

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• ????? Animal
• ????
• Wipe
• ????????
• Killing, burning or deep
• ????
• Isolation and treatment
• ???????
• Vaccination and quarantine

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• ????????
• measures for route of transmission
• ?? Disinfection
• ??
• ????? Preventive disinfection         
• ????? Foci disinfection

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• ??

• ???? Disinfection at any time    
• ???? Terminal disinfection

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• ????????
• Measures for the susceptible
• ???? Immunization
• ???? Drug prevention
• ???? Personal Protection

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