Principles of Communicable Diseases Epidemiology

							PREVENTION /CONTROL and
ERADICATION of
Communicable Diseases
 Dr. Abdalla Abdelwahid Saeed
 Consultant
 Community Medicine

 Tuesday 4.11.1431H
PREVENTION/CONTROL AND
ERADICATION OF COMMUNICABLE
DISEASES
 OBJECTIVES :
 1-REVIEW OF COMMUNICABLE DISEASE
  EPIDEMIOLOGY
 2-DEFINTIONS OF TERMS:
 PREVENTION, CONTROL, ERADIACTION
 PRINCIPLES OF PREVENTION, CONTROL
  AND ERADICATION OF COMMUNICABLE
  DISEASES
 ERADICATED DISEASES ( SMALL POX)
 NON COMMUNICABLE DISEASES
  PREVENTION/CONTROL
DEFINITIONS

 PREVENTION : PRIMARY PREVENTION OF
  DISEASE- DISEASE WILL NOT OCCUR
 CONTROL : DECREASING LEVEL OF
  DISEASE TO ACCEPTABLE LEVEL OF NO
  CONCERN TO AUTHORITY AND COMMUNITY
 ERADICATION: DECREASING LEVL OF
  DISEASE TO ZERO LEVEL. DISEASE DOES
  NOT OCCUR AGAIN
LEVELS OF PREVENTION
 1-PRIMORDIAL – PREVENT RISK
  FACTORS
 2-PRIMARY : REVERSE , REDUCE
  RISKFACTORS
 3-SECONDARY : PROMPT
  DIAGANOSIS AND TREATMENT
 4-TERTIARY: REHEBILITATION
Definitions
 Control: The reduction of disease incidence,
  prevalence, morbidity or mortality to a locally
  acceptable level as a result of deliberate efforts;
  continued intervention measures are required to
  maintain the reduction. Example: diarrhoeal diseases.
 Elimination of disease: Reduction to zero of the
  incidence of a specified disease in a defined
  geographical area as a result of deliberate efforts;
  continued intervention measures are required.
  Example: neonatal tetanus.
 Elimination of infections: Reduction to zero of the
  incidence of infection caused by a specific agent in a
  defined geographical area as a result of deliberate
  efforts; continued measures to prevent re-
  establishment of transmission are required. Example:
  measles, poliomyelitis.
Definitions
 Eradication: Permanent reduction to
  zero of the worldwide incidence of
  infection caused by a specific agent
  as a result of deliberate efforts;
  intervention measures are no longer
  needed. Example: smallpox.
 Extinction: The specific infectious
  agent no longer exists in nature or in
  the laboratory. Example: none.
Magnitude
   COMMUNICABLE DISEASES
   ( DISEASES TRANSMITTED FROM PERSON TO PERSON) WERE
    IMPORTANT PROBLEMS WORLDWIDE.
   WITH DEVELOPMENT AND IMPROVED QUALITY OF LIFE THEY
    WERE SIGNIFICANTLY REDUCED IN TERMS OF INCIDENCE AND
    PREVALENCE IN MOST DEVELOPED ( RICH ) COUNTRIES. THEY
    ARE STILL MAJOR HEALTH PROBLEMS IN MANY DEVELOPING
    COUNTRIES.
   IN THE KINGDOM SOME OF THEM ARE STILL PREVALENT AND
    HAJJ AND OMRA SEASONS ARE RISK SEASONS FOR IMPORTING
    SOME INFECTIOUS DISEASES.
   EVEN IN DEVELOPED DISEASES SOME INFECTIOUS DISEASES
    STARTED TO REAPPEAR AGAIN ( REEMERGING ) AND SOME NEW
    DISEASE ARE APPEARING IN THE WORLD ( EMERGING DISEASES)
    SUCH AS SARS.
   SO THE STUDY OF INFECTIOUS DISEASES IS STILL IMPORTANT
    FOR HEALTH STUDENTS IN THE KINGDOM AND IN OTHER
    COUNTRIES.
REVIEW OF EPIDEMIOLOGY OF
COMMUNICABLE DISEASES
 FOR ANY INFECTIOUS DISEASE TO BE
  PRESENT AND BE TRANSMITTED IN THE
  COMMUNITY TWO FACTORS ARE
  ESSENTIAL :
 1- SOURCE :
 THERE MUST BE A SOURCE FOR THE
  DISEASE.
 SOURCE IS HUMAN , ANIMAL ,
  ENVIRONMENT ETC… WHERE THE
  CAUSATIVE AGENT IS FOUND AND BE
  TRANSMITTED TO OTHERS.
CONTD…
 2- SUSCEPTIBLE HOST : PERSON AT
  RISK BECAUSE IS EXPOSED TO
  DISEASE AND HAS NO IMMUNITY OR
  PROTECTION AGAINST THE DISEASE.
CONTD…
 IN SOME DISEASES A THIRD FACTOR
  IS NECESSARY SUCH A VEHICLE OR
  A VECTOR TO TRANSMIT THE
  CAUSATIVE AGENT FROM SOURCE TO
  SUSCEPTIBLE HOST
EPIDEMIOLOGY OF
COMMUNICABLE DISEASES
   A HUMAN SOURCE CAN BE :
   1.1. PATIENT WITH SYMPTOMS
   1.2. CARRIER WITHOUT SYMPTOMS
   THE CARRIER CAN BE :
   1.2.1. INCUBATING CARRIER DURING THE INCUBATION
    PERIOD WHICH IS THE PERIOD BETWEEN ENTRANCE OF
    CAUSATIVE AGENT AND APPEARANCE OF SYMPTOM
   1.2.2. CONVALASCENT CARRIER DURING THE
    CONVALASCENCE PERIOD AFTER THE DISAPPEARNCE OF
    SYMPTOMS
   CARRIERS CAN BE ACUTE (TEMPORARY) CARRIER FOR
    SHORT PERIOD OR CHEONIC ( PERMENANT ) FOR LONG
    PERIOD.
   2- SUSCEPTIBLE HOST : PERSON AT RISK BECAUSE IS
    EXPOSED TO DISEASE AND HAS NO IMMUNITY OR
    PROTECTION AGAINST THE DISEASE.
EPIDEMIOLOGY OF
COMMUNICABLE DISEASES
 IN SOME DISEASES A THIRD FACTOR IS
  NECESSARY SUCH A VEHICLE OR A
  VECTOR TO TRANSMIT THE CAUSATIVE
  AGENT FROM SOURCE TO SUSCEPTIBLE
  HOST. SO THE TRANSMISSION CAN BE
  DIRECT FROM SOURCE TO SUSCEPTIBLE
  OR INDIRECT REQUIRING A VEHICLE OR A
  VECTOR. A VEHICLE IN NON LIVING SUCH
  AS AIR, FOOD, WATER, FOMITES (
  CLOTHES ETC.. ) , DISHES, FORK,
  SPOONS, KNIVES ETC…
CONTD…..
 A VECTOR IS A LIVING AGENT CAPABLE OF
  THRANSMITTING THE DISEASE SUCH AS
  MOSQUITOE, FLIES, LICE, FLEAS ETC… . THIS
  TRANSMISSION CAN BE BIOLOGICAL IF CAUSATIVE
  AGENT ENTERS INSIDE THE BODY AND CHANGE IN
  FORM ( DEVELOPMENT) ONLY KNOWN AS
  CYCLODEVELOPMENTAL ( SUCH AS FILARIASIS –
  ELEPHANTIASIS ) WHERE MICROFILARIA DEVELOPS
  AND CHANGE INTO ADULT WORM WITHOUT
  MULTIPLICATION )- OR KNOWN AS PROPAGATIVE(
  MULTIPLICATIVE) IF THERE IS ONLY
  MULTIPLICATION WITHOUT DEVELOPMENT SUCH AS
  IN PLAGUE
CONTD…..
    OR CAN BE CYCLOPRORGATIVE IF THERE IS BOTH
    DEVELOPMENT AND MULTIPLICATION SUCH AS NIN
    MALARIA WHERE THE GAMETOCYTES INCREASE IN
    NUMBERS AND CHANGE TO INFECTIVE STAGE OF
    SPOROZOITES. IN SOME DISEASES THERE IS A NEED
    FOR AN INTERMEDIATE HOST ( WHERE NON SEXUAL
    MULTIPLICATION OF THE CAUSATIVE AGENT TAKES
    PLACE ) SUCH AS SNAILS IN SCHISTOSOMISIS
    WHERE MIRACIDIA FROM THE EGGS DEVELOP INTO
    CERCARIA WHICH ARE THE INFECTIVE STAGE TO
    THE DEFINITIVE HOST WHERE THE SEXUAL
    MATURATION AND MULTIPLICATION TAKE PLACE.
PRINCIPLES OF CONTROL OF
COMMUNICABLE DISEASES:


 TO CONTROL ANY COMMUNICABLE
  DISEASE YOU HAVE TO BREAK THE
  INFECTIOUS CIRCLE AT THE
  SOURCE, SUSCEPTIBLE HOST OR
  VECTOR OR IN ALL OF THEM AS
  FOLLOWS :
CONTROL            CONTD…
 A- SOURCE    :

 HUMAN :
 PATIENT :
 1-TREAT ( CORRECT DRUG, DOSE , DURATION ) ,
  CONFIRM CURE BY DISAPPEARNCE OF SYMPTOMS
  AND SIGNS AND LABORATORY TESTS.THE PATIENT
  HAVE THE DISEASE
 2- ISOLATION : THIS IS NECESSARY IF DISEASE IS
  DIRECTLY TRANSMITTED WITH LOW OR NO
  CARRIERS AND THE DISEASE IS VERY SERIOUS . IT
  IS MORE PRACTICAL IF DISEASE IS OF SHORT
  DURATION. IT IS USUALLY NOT DONE FOR VERY
  MILD DISEASES.ISOLATION CONTINUES TILL THE
  PATIENT IS FULLY CURED .
CONTROL    CONTD
 ISOLATION CAN ALSO BE FOR
  CERTAIN SYSTEMS OF THE
  PATIENT AND NOT FOR THE
  WHOLE PATIENT –
 2.1. RESPIRATORY ISOLATION
 2.2. ENTERIC ISOLATION
 2.3. SEXUAL ISOLATION
 2.4. CONTACT ISOLATION
CONTROL           CONTD
    HEALTH EDUCATION : THIS IS IMPORTANT FOR ALL
    3-
  DISEASES. THIS INCLUDE THE MESSAGE , THE
  METHOD , FOR WHOM AND WHY.HOW TO AVOID
  INFECTING OTHERS.
 4-DISINFECTION: KILLING CAUSATIVE AGENTS
  COMING OUT OF THE PATIENT . THIS CAN BE
  CONCURRENT ( CONTINUOUS) OR TERMINAL ( AT END
  OF DISEASE IF PATIENT IS TREATED OR DIED)
 CARRIER : LOOK FOR CARRIERS IN CONTACTS OF
  PATIENTS AND OTHERS BY EXAMINATION AND LAB.
  INVESTIGATIONS. IF FOUND APPLY THE SAME
  MEASURES APPLIED TO PATIENTS.
 IF SOURCE IS ANIMAL ( ZOONOSIS) YOU CAN TREAT
  OR ERADICATE . THE CARRIER HAS THE INFECTION.
CONTROL       CONTD
 5- QUARANTINE : OF CLOSE CONTACTS OF
  OPEN CASES OF SOME DISEASES
  DIRECTLY TRANSMITTED FOR THE
  MAXIMUM INCUBATION PERIOD.
  QUARNTINE CAN BE :
               CONTROL CONTD
 5.1. STRICT QUARANTINE AS IN
  ISOLATION
 5.2. MODIFIED QUARANTINE ( PERSON
  SURVEILLANCE – MONITORING) WHERE
  THE PERSON IS OBSERVED AT HOME OR
  WORK AND REQUESRED TO REOPRT IF
  SYMPTOMS ARISE OR REPORT REGULARLY
  FOR MEDICAL EXAMINATION.
CONTROL CONTD/
DISEASE PREVENTION
 B- SUCECPTIBLE HOST:
 1- RAISE SOCIOECONOMIC CONDITIONS
  AND IMPROVE QUALITY OF LIFE-
  ENVIRONMENTAL SANITATION – SAFE ,
  ADEQUATE WATER SUPPLY, PROPOER
  REFUSE COLLECTION AND DISPOSAL ,
  PERSONAL AND GENERAL HGYIENE AND
  FOOD AND FOOD HANDLERS HYGIENE,
  LITERACY, HEALTH SERVICES, HOUSING
  ETC…..
 2- HEALTH EDUCATION- MESSAGE ,
  METHOD AND WHY . HOW TO AVOID
  CONTRACTING THE DISEASE .
CONTROL     CONTD
 3- SPECIFIC PROTECTION:
 3.1.PHYSICAL ENVIRONMENT,
  PROTECTIVE CLOTHES, SCREENS,
  BED NETS
 3.2 CHEMICAL : PROTECTION BY
  DRUGS ( CHEMOPROPHYLAXIS)
 3.3 BIOLOGICAL : BY PASSIVE (
  IMMUNOBLOBULINS) OR ACTIVE (
  VACCINES ) IMMUNIZATION OR
  ACOMBINATION OF BOTH
IMMUNIZATION
 VACCINES : DERIVED FROM CAUSATIVE AGENTS
 ACTIVE by giving vaccines derived from
  causative agent these can be live, live
  attenuated (weakened), killed (INACTIVATED)
  or toxoid (weakened toxins)- body will make
  antibodies
 GOOD VACCINE is safe, effective, cheap, easy to
  administer, one dose, acceptable
 EXPANDED PROGRAM OF IMMUNIZATION (
  E.P.I.)
 OTHER VACCINES
 ADULT VACCINATION
CONTROL     CONTD
 C- VECTOR OR INTERMEDIATE HOST
  : ERADICATE OR CONTROL VECTOR
  OR INTERMEDIATE HOST OR
  DECREASE CLOSE CONTACT OF
  VECTOR WITH BOTH SOURCE AND
  SUSCEPTIBEL HOST BY:
 1. PHYSICAL METHODS : CHANGE
  ENVIRONMENT SO THAT IT IS NO
  LONGER SUITABLE FOR PRESENCE
  OR MULTIPLICATION OF VECTOR
  SUCH AS DRYING OR FILLING OF
  SWAMPS AND CANALS.
CONTROL          CONTD
 2- CHEMICAL : BY CHEMICAL COMPOUNDS SUCH AS
  INSECTICIDES FOR INSECTS, RODENTICIDES FOR
  RODENTS AND MOULLSCIDES FOR SNAILS. INSECT
  REPELLANTS ARE CHEMICAL COMPOUNDS APPLIED
  TO SKIN SURFACE OF HUMANS TO REPELL INSECTS
  FROM BITING.
 3- BIOLOGICAL : BY CERTAIN ANIMALS WHICH KILL
  OR EAT VECTOR SUCH AS GAMBUSIA FISH WHICH
  EATS THE LARVAE OF CERTAIN MOSQUITOES OR
  CERTAIN PLANTS WHICH CAN KILL THE VECTOR OR
  THE INTERMEDIARE HOST.
Eradication
 Eradication is the reduction of an
  infectious disease's prevalence in the global
  human or animal host population to
  zero.[1] It is sometimes confused with
  elimination, which describes either the
  reduction of an infectious disease's
  prevalence in a regional population to zero,
  or the reduction of the global prevalence to
  a negligible amount
Eradication Attempts
 Seven attempts have been made to date to eradicate
  infectious diseases in humans globally - four aborted
  programs targeting hookworm, malaria, yaws, and
  yellow fever, one successful program targeting
  smallpox and two ongoing programs targeting
  poliomyelitis and dracunculiasis. Five more infectious
  diseases have been identified as of April 2008 as
  potentially eradicable with current technology by the
  Carter Center International Task Force for Disease
  Eradication - measles, mumps, rubella, lymphatic
  filariasis and pork tapeworm
ERADICATION
 SMALL POX: has been eradicated from the world but
  we teach it to know how was it eradicated and
  whether we can use similar or modified strategies to
  eradicate other infectious diseases Occurrence:
  previously worldwide-, last natural human case 1977
  in Somalia . last lab. case in 1978, in Birminghm , Uk.
  eradication certified by W.H.O in 1980.
Small pox eradication
    live attenuated vaccine, safe , effective, easy to
    administer – skin scratching -
   eradication of smallpox:
   phases : 1- preparatory phase
   2- attack phase ( vaccination )
   3- consolidation phase      4- maintenance phase
   factors helped in eradication success :
   serious disease, international, direct transmission, no
    vectors, no non human source, no carriers, easy
    recognizable clinical features, excellent vaccine , but
    international cooperation was very effective.
Terms

 Containment – to contain the disease as to prevent it from
  becoming a worse problem. Containment is usually the only
  option available for the majority of infectious diseases.
 Elimination – to eliminate the disease even though the infectious
  agent may remain e.g. rabies and polio had been eliminated in
  many countries, and probably SARS in 2003.
 Eradication – to eradicate the infectious agent altogether
  worldwide e.g. smallpox
 Eradication of Smallpox
The initial strategy was separated into 3 phases;
   Attack phase - This applied to areas where the incidence of
    smallpox exceeded 5 cases per 100,000 and where vaccination
    coverage was less than 80%. Attention was given to mass
    vaccination and improvement in case surveillance and reporting.
    This phase lasted from 1967-1973. A large amount of financial
    resoureces were provided for setting up surveillance centres and
    reference centres. Priority was given to Brazil, sub-saharan African,
    S.Asia and Africa.
Eradication of Smallpox

  Consolidation Phase - In areas where the incidence was less than 5
   cases per 100,000 and vaccination coverage exceeded 80%, the
   objective was the elimination of smallpox. Vaccination uptake was
   to be maintained and surveillance improved. Facilities should be
   made available for isolation.
  Maintenance Phase - once smallpox had been eliminated, it was
   essential it was not reintroduced. This phase was entered in 1978.
   In 1980, the world was declared to be free of smallpox.
Features that made Smallpox
an eradicable disease

  1. A severe disease with morbidity and mortality
  2. Considerable savings to developed non-endemic countries
  3. Eradication from developed countries demonstrated its
   feasibility
  4. No cultural or social barriers to case tracing and control
  5. Long incubation period
  6. Infectious only after incubation period
  7. Low communicability
Contd..
 8. No carrier state
 9. Subclinical infections not a source of infection
 10. Easily diagnosed
 11. No animal reservoir
 12. Infection confers long-term immunity
 13. one stable serotype
 14. Effective vaccine available
Contd..
2 strategies used:
  1. vaccination campaigns to immunize
  80% of the population.
  2. surveillance and containment of cases
  and outbreaks.
EPIDEMIOLOGY OF NON
COMMUNICABLE DISEASES


  DEFINITION : NO AGREED DEFINITION
  “ IMPAIRMENT OF BODY STRUCTURE AND / OR FUNCTION
  PERSISITING FOR LONG PERIOD NECESSITATING MODIFICATION
  OF NORMAL LIFE” EUROPE
  “ IMPAIRMENTS, DEVIATIONS FROM NORMAL WHICH ARE :
  PERMENANT , WITH RESIDUAL DISABILITY, ,NON REVERSIBLE
  PATHOLOGY, REQUIRES PATIENTS TRAINING / REHABILITATION
  WITH LONG PERIOD OF SUPERVISION” USA
   MAGNITUDE OF PROBLEM :
   INCEASING WORLDWIDE AMONG ADULTS,. CVD AND
    CANCERS CAUSE 70 - 75 % OF DEATHS IN DEVELOPED
    COUNTRIES. THE INCREASE IS DUE TO INCREASED LIFE
    EXPECTANCY- CHANGE IN LIFESTYLE , , MODERN MEDICAL
    CARE,
   SHARED RISK FACTORS:
   SMOKING, ALCOHOL, LIFE-STYLE, ENIRONMENT RISKS,
    STRESS, FAILURE TO UPTAKE PREVENTIVE SERVICES.
   GAPS IN NATURAL HISTORY :
   ABSENCE OF KNOWN AGENT
   MULTIFACTORIAL
   LIFE- STYLE
   IDEFINITE ONSET
   PREVENTION AND CONTROL STRATEGIES SHOULD TAKE ALL
    THESE FACTORS IN CONSIDERATION USING A
    COMPREHENSIVE AND INTEGRATED APPROACH.
Problems in chronic non
communicable diseases0
   lack of specific causative agent
   Indefinite onset of disease
   Long latent period
   Multiple possible etiological factors

Identify Causative factor(s)
Identify risk factors
 Risk factors :
 A- Modifiable
 B- Non modifiable
NON COMMUNICABLE DISEASE
( MOSTLY CHRONIC
 LEVEL OF PREVENTION
 PRIMORDIAL PREVENTION : prevent occurrence
  of risk factors- counseling, health education
 PRIMARY PREVENTION: prevent occurrence of
  disease- by reversing or reducing risk factors by
  health education
 SECONDARY PREVENTION: prevent spread or
  complications by screening programs ( early
  diagnosis and proper and quick treatment)
 TERTIARY PREVENTION: prevent disability by
  rehabilitation, physical, social, psychological and
  occupational
THANK YOU
 BEST WISHES TO ALL




                 THANK YOU
                 THANK YOU