Contents regarding epidemiology in community health nursing for first year gnm students.

1. EPIDEMIOLOGY
NANDANA NARAYANAN K P
NURSING TUTOR
DEPT OF COMMUNITY HEALTH NURSING
SEVANA SCHOOL OF NURSING
PATTAMBI

2. DEFINITION
MAIN COMPONENTS OF EPIDEMIOLOGICAL DEFINITION INCLUDE;
• STUDY OF THE FREQUENCY OF DISEASE
• STUDY OF THE DISTRIBUTION OF DISEASE
• STUDY OF THE FREQUENCY OF DISEASE
ACCORDING TO JOHAN.M.LAST
THE STUDY OF THE DISTRIBUTION AND DETERMINANTS OF HEALTH RELATED STATES OR EVENTS
IN SPECIFIED POPULATION AND THE APPLICATION OF THIS STUDY TO THE CONTROL OF HEALTH
PROBLEM.

3. AIMS
AIMS PUT FORWARD BY INTERNATIONAL
EPIDEMIOLOGICAL ASSOCIATION (IEA);
• TO DESCRIBE THE DISTRIBUTION AND
MAGNITUDE (DEGREE OF SIZE) OF
HEALTH AND DISEASE PROBLEMS
AMONG INDIVIDUALS AND GROUPS
(HUMAN POPULATION).
• TO IDENTIFY THE ETIOLOGICAL FACTORS
(RISK FACTORS) IN THE PATHOGENESIS
(SOURCE OF CAUSE) OF DISEASE.

4. • TO PROVIDE DATA FOR PLANNING,
IMPLEMENTATION AND EVALUATION OF SERVICES
FOR THE PREVENTION, CONTROL AND
TREATMENT OF DISEASE AND IN SETTING UP OF
PRIORITIES AMONG THOSE SERVICES.
EPIDEMIOLOGICAL INVESTIGATION
IT INCLUDES 6 STEPS:
•1. ESTABLISHING THE OCCURRENCE OF A PROBLEM.
•2. VERIFYING THE DIAGNOSIS.
•3. COLLECTING RELATED DATA.

5. 4. DESCRIBING THE
OCCURRENCE IN TERMS OF
PERSON, PLACE AND TIME.
5. FORMULATING
HYPOTHESIS.
6. TESTING OF HYPOTHESIS.

6. EPIDEMIOLOGICAL METHODS/ APPROACH
1.DESCRIPTIVE METHOD
 PLACE
 PERSON
 TIME
2.ANALYTIC METHOD
a. EXPERIMENTAL APPROACH
 CLINICAL TRIALS
 COMMUNITY TRIALS
• SINGLE BLIND
• DOUBLE BLIND
• TRIPLE BLIND

7. b. OBSERVATIONAL
• RETROSPECTIVE (CASE CONTROL)
• PROSPECTIVE (COHORT OR LONGITUDINAL)
• CROSS SECTIONAL

8. 1.DESCRIPTIVE METHOD
 THEY ARE CONCERNED WITH THE AMOUNT AND DISTRIBUTION OF DISEASE IN THE
POPULATION AND PROVIDE DATA NEEDED TO FORMULATE HYPOTHESIS.
 THEY DESCRIBE DISEASE OCCURRENCE IN RELATION TO PLACE, PERSON AND TIME.
MAIN OBJECTIVES:
 TO PROVIDE A DATABASE FOR PLANNING, PROVIDING, AND EVALUATING HEALTH SERVICES.
 TO EVALUATE THE TRENDS IN HEALTH SECTOR AND PROVIDE A
BASIS FOR COMPARISONS AMONG GROUPS.
 TO IDENTIFY PROBLEMS FOR FURTHER ANALYSIS.

9. i. PERSON
• VARIOUS DEMOGRAPHIC AND SOCIAL CHARACTERISTICS OF PERSONS ARE STUIED.
• AMONG THESE AGE, SEX, MARITAL STATUS, RELIGION, OCCUPATION, SOCIO-ECONOMIC
STATUS ETC ARE VERY IMPORTANT.
ii. PLACE
• NATURE AND OCCURRENCE OF DISEASE ARE DIFFERENT IN DEVELOPED AND UNDEVELOPED COUNTRIES.
• SO INADDITION TO PERSONS/POPULATION CHARACTERISTICS, GEOGRAPHIC
LOCALITY IS ALSO MOST IMPORTANT.
iii. TIME
• THERE MAY BE LONG-TERM VARIATIONS IN DISEASE OCCURRENCE , PERIODIC/ CYCLIC
CHANGES, OR SHORT-TERM FLUCTATIONS WHICH OCCUR WITH EPIDEMICS.

10. • MANY DISEASE REPRESENT SEASONAL VARIATIONS.
EG: INFLUENZA MOST COMMONLY OCCUR DURING DECEMBER-MARCH OF EVERY YEAR.
• LONG-TERM VARIATIONS REPRESENT THE CHANGING PATTERNS OF DISEASE.
2. ANALYTIC METHOD
 CARRIED OUT TO TEST THE HYPOTHESIS.
 HYPOTHESIS ARE FORMULATED FROM THE INFORMATION GATHERED FROM THE DESCRIPTIVE METHOD.
 CONCERNED WITH FINDING THE REASONS FOR THE FREQUENCY OF OCCURRENCE OF DISEASE IN A
POPULATION.
 IT DEMONSTRATES THE HYPOTHESIZED ASSOCCIATION BETWEEN DISEASE OCCURRENCE AND POINTED
OUT ANTECEDENT FACTORS.

11.  IT INCLUDES TWO APPROACHES:
a. EXPERIMENTAL APPROACH
b. OBSERVATIONAL APPROACH
a. EXPERIMENTAL APPROACH
 USED TO TEST HYPOTHESIS IN ALMOST ALL SCIENTIFIC RESEARCHES.
 BUT ITS APPLICATION IN EPIDEMIOLOGY IS CONFINED TO EXPERIMENTS AIMED AT PREVENTION
OR TREATMENT OF DISEASE.
 EG: TO DETERMINE CAUSE- EFFECT RELATIONSHIP;
INVESTIGATOR CONTROLS ONE FACTOR; INDEPENDENT VARIABLE
AND MEASURES SUBSEQUENT EFFECT ON DEPENDENT VARIABLE.

12. IT INCLUDES TWO TYPES:
• CLINICAL TRIALS
• COMMUNITY TRIALS
USES OF CLINICAL TRIALS
 TO TEST THE EFFECTIVENESS OF ADRUG OR TREATMENT ( THERAPEUTIC TRIAL)
 TO KNOW THE EFFICACY OF A PREVENTIVE MEASURE OR PROCEDURE (PREVENTIVE TRIAL)
 TO DETERMINE THE EFFECT OF CONTROLLING RISK FACTORS FOR A GIVEN DISORDER
(INTERVENTION TRIAL)

13. USES OF COMMUNITY TRIAL
 USED TO TEST THE EFFICACY OF PROCEDURE ON THE GROUPS OF INDIVIDUALS.
 EG: EVALUATION OF DENTAL DISORDERS IN A COMMUNITY WITH OR WITHOUT FLUORIDE ADDED TO
DRINKING WATER.
 TO AVOID FAVOURITISM OR BIAS IN EXPERIMENTAL METHODS BY INVESTIGATOR, IT INCLUDES;
 SINGLE BLIND= SUBJECTS ARE NOT AWARE OF THE EXPERIMENT
 DOUBLE BLIND= NEITHER SUBJECTS NOR INVESTIGATOR KNOWSTO WHICH GROUP SUBJECT
BELONGS.
 TRIPLE BLIND= INVESTIGATORS,SUBJECT ALONG WITH DATA ANALYZER DO NOT KNOW GROUP
ASSIGNMENT.

14. b.OBSERVATIONAL APPROACH
• MOST COMMONLY APPLIED IN EPIDEMIOLOGY.
• SUBJECT OF INTEREST IS INDIVIDUAL WITHIN THE POPULATION AND OBJECT IS TO TEST
HYPOTHESIS.
• INVESTIGATOR OBSERVES THE OCCURRENCE OF DISEASE IN INDIVIDUALS WHO ARE
ALREADY GROUPED ON THE BASIS OF CERTAIN CHARACTERISTICS.
• SOME VARIABLES SUCH AS AGE, SEX, OCCUPATION, SOCIAL STATUS ETC (CONFOUNDING
VARIABLES) MAY DIFFER IN PREVIOUS EXPERIENCES.
• INCLUDES 3 TYPES :
 RETROSPECTIVE (CASE-CONTROL)
 PROSPECTIVE (COHORT)
 CROSS SECTIONAL

15. RETROSPECTIVE (CASE-CONTROL)
 INCLUDES TWO POPULATION GROUP; CASE AND CONTROL.
 IT COMPARES INDIVIDUAL WHO ARE DIAGNOSED WITH CERTAIN PROBLEM (CASES) TO
WHO DO NOT HAVE DISEASES (CONTROL).
 IT DETERMINES ANY DIFFERENCE BETWEEN THE GROUP EXISTS IN EXPOSURE TO ONE
OR MORE ANTECEDENT FACTORS.

16. CASE CONTROL
STUDY DESIGN

17. PROSPECTIVE STUDY (COHORT STUDY)
 USUALLY CARRIED OUT AFTER IDENTIFICATION OF POSSIBLE DISEASE CAUSING
FACTORS THROUGH RETROSPECTIVE STUDY.
 CONFIRMS THE PREVIOUSLY OBSERVED ASSOCIATION BETWEEN SUSPECTED CAUSE
AND DISEASE.
 SUPPLIES MORE DEFINITIVE INFORMATION.

18.  OTHER SYNONYMOUS TERMS= INCIDENCE STUDY, FORWARD LOOKING STUDY.
 COHORT= WORD INDICATES A GROUP OF PEOPLE WHO HAVE COMMON CHARACTERISTICS,
EXPERIENCES OR EXPOSURE WITHIN A DEFINED PERIOD OF TIME.
 COHORT IS FREE OF DISEASE AT THE TIME OF IDENTIFICATION AND IS FOLLOWED OVER A
PERIOD OF TIME, TO KNOW THE DIFFERENCES IN THE RATE AT WHICH THE
DISEASE DEVELOPS IN RELATION TO COMMON EXPOSURE.
 REQUIRES MORE TIME TO COMPLETE (LONG TERM) AND
EXPENSIVE.

19. STEPS
 SELECTION OF SUBJECT FOR STUDY.
 OBTAINING DATA ABOUT EXPOSURE.
 SELECTION OF COMPARISON GROUPS.
 FOLLOW UP AND ANALYSIS OF DATA IN TERMS OF INCIDENCE RATE.
 ESTIMATION RISK.
ADVANTAGES
 PROVIDES MEASUREMENT OF THE RELATIVE RISK.
 LESS LIKELY TO BE BIASED.

20. COHORT STUDY
DESIGN

21. CROSS-SECTIONAL STUDY
 HAS COMMON ELEMENTS OF BOTH CASE CONTROL AND COHORT STUDY.
 IT EXAMINES THE PRESESNCE OR ABSENCE OF A RELATIONSHIP BETWEEN
IDENTIFIED FACTORS AND ALREADY EXISTING FACTORS AT A SINGLE POINT OF TIME.
 PROVIDES DATA ON RELATIONSHIP OF PREVIOUS EXPOSURE OR PREVIOUS FACTORS
AND THE PRESENT EXISTENCE OF A PARTICULAR DISEASE.

22. CROSS-
SECTIONAL
STUDY DESIGN

23. BASIC TOOLS FOR MEASUREMENT
AFTER COMPLETING THE STUDIES, THE GATHERED RAW MATERIAL/DATA ARE
ORGANIZED, CATEGORIZED FOR COMPARISON AND EVALUATION OF STUDY
RESULTS.
COMMON TOOLS USED ARE:

24. RATES
• DEMONSTRATE QUANTITATIVE
CHARACTERISTICS OR ATTRIBUTES.
• WIDELY USED FOR THE
MEASUREMENT OF AMOUNT OF
DISEASE OR THE NUMBER OF
THOSE AFFECTED IN A HUMAN
POPULATION.

25. DEFINITION
MEASUREMENT OF A SPECIFIC EVENT, CONDITION OR DISEASES IN A GIVEN
POPULATION
WITHIN A SAME AREA.
RATE= NO OF AFFECTED IN A TIME PERIOD
TOTAL POPULATION IN A SAME AREA

26. 1.DEMOGRAPHIC RATES
IT DENOTES TWO PARTS:
 NUMERATOR= EVENTS OCCURRING IN A DEFINED POPULATION DURIN A SPECIFIED TIME PERIOD.
 DENOMINATOR= POPULATION OR TOTAL EVENTS.
 EG: INFANT MORTALITY RATE
MATERAL MORTALITY RATE
2.MORBIDITY RATES
 GENERALLY PRESENTED AS INCIDENCE RATE AND PREVALANCE RATE.
 MORBIDITY INDICATES, “ ANY DEPARTURE,SUBJECTIVE OR OBJECTIVE FROM A STATE OF
PHYSIOLOGICAL WELL-BEING.

27. 3.INCIDENCE RATE
 IT INDICATES NUMBER OF NEW CASES OF A PARTICULAR DISEASE IN A POPULATION OVER A PERIOD OF
TIME.
 PROVIDES DIRECT MEASURE OF THE RATE AT WHICH INDIVIDUAL IN A GIVEN POPULATION BECOMES ILL.
INCIDENCE RATE= NO OF NEW CASES OF A DISEASE DURING A GIVEN TIME PERIOD
*1000
POPULATION AT RISK DURING THAT TIME PERIOD

28. 4. PREVALANCE RATE
 IT INDICATES NO OF EXISTING CASES OF DISEASES IN TOTAL POPULATION AT A PARTICULAR POINT OF
TIME.
 IT IS RATIO RATHER RATE.
 IT IS OF TWO TYPES;
 POINT PREVALANCE
 PERIOD PREVALANCE
POINT PREVALANCE= NO OF EXISTING CASES OF A DISEASE AT POINT OF TIME *1000
TOTAL POPULATION AT SAME POINT OF TIME
 WHEN DISEASE IS CURED, PREVALANCE IS DECREASED.

29. RATIO
 VALUE OBTAINED BY DIVIDING ONE BY ANOTHER.
 A RATIO OFTEN COMPARES TWO RATES.
 EG: COMPARING DEATH RATE OF MEN AND WOMEN AT A
GIVEN AGE (60YRS)
RATIO=NO OF DEATH OF MEN UPTO 60YRS OF AGE IN A GIVEN PERIOD
NO OF DEATH OF WOMEN UPTO 60YRS OF AGE IN SAME PERIOD

30. DISTRIBUTION
• INDICATES THE NUMBER OF INDIVIDUALS
FOUND TO HAVE EACH VALUE OR EACH SMALL
RANGE OF VALUE.
• FREQUENCY DISTRIBUTION DEMONSTRATES
THE QUALITATIVE CHARACTERISTICS= HEIGHT,
WEIGHT OR INVESTIGATION VALUES ETC.

31. DYNAMICS OF DISEASE TRANSMISSION
DYNAMICS OF DISEASE TRANSMISSION INVOLVES THE CHAIN OF INFECTION. IT INCLUDES PROCEEDS
OF TRANSMISSION OF DISEASE FROM RESERVOIR OR SOURCE OF INFECTION TO SUSCEPTIBLE HOST.
STEPS OF TRANSMISSION ARE :

33. 1.SOURCE OR RESERVOIR
• FIRST STEP OR LINK OF CHAIN OF INFECTION STARTS.
• IT INVOLVES ; PRESENCE OF PATHOGENS, THEIR HABITAT AND
PORTAL OF EXIST.
• ORGANISMS OR AGENT HAVING THE PATHOGENICITY REMAIN
IN THE SOURCE OR RESERVOIR.

34. SOURCE
IT MEANS THE PERSON, ANIMAL, OBJECT/ SUBSTANCE FROM WHICH AN INFECTIOUS
AGENT PASSES OR DISSEMINATED TO THE HOST. IT INDICATES THE IMMEDIATE
SOURCE OF INFECTION.
RESERVIOR
IT MEANS THE PLACE OF INFECTIOUS ORGANISM WHERE IT NORMALLY LIVES,
SURVIVES AND MULTIPLIES. THE NATURAL HABITAT OF AN ORGANISM MAY BE
HUMAN, ANIMAL OR ENVIRONMENT.
THERE ARE 3 CATEGORIES OF RESERVIOR ;
 HUMAN
 ANIMAL
 ENVIRONMENT

35. a. HUMAN RESERVIOR
IT MAY BE OF TWO TYPES;
 CASE
 CARRIER
 CASE - INDICATES A PERSON WITH A PARTICULAR DISEASE,
HEALTH DISORDER OR UNDER INVESTIGATION.
 CASES ARE CLASSIFIED INTO:
 CLINICAL - HAVING THE CLEAR-CUT MANIFESTATIONS (FROM MILD TO SEVERE ILLNESS)
 SUB-CLINICAL - NO CLEAR-CLINICAL MANIFESTATIONS, INVESTIGATIONS SUGGEST THE PRESENCE
OF INFECTIONS.
 LATENT - NO CLINICAL MANIFESTATIONS, AS WELL AS ROUTINE INVESTIGATIONS DO NOT
DEMONSTRATE THE PRESENCE OF DISEASE.
 EG : HERPES SIMPLEX
CLINICAL
SUB-CLINICAL
LATENT

36.  CARRIER - IT IS AN INFECTED INDIVIDUAL WITH NO APPARENT DISEASE THAT SERVES AS A
POTENTIAL SOURCE OF INFECTION TO OTHERS.
 CARRIERS CAN BE GROUPED ON THE BASIS OF;
PORTAL OF
EXIT
DURATION
DISAESE
CONDITION

37. DISEASE
CONDITION
• INCUBATORY
• CONVALESCENT
• HEALTHY
DURATION
• TEMPORARY
• CHRONIC
PORTAL OF EXIT
• URINARY TRACT
• INSTENINAL
TRACT
• RESPIRATORY
TRACT
• OTHERS
1.INCUBATORY CARRIERS
THESE ARE THOSE WHO SHED THE INFECTIOUS AGENT DURING THE INCUBATION PERIOD OF DISEASE.
ie, THEY ARE CAPABLE OF INFECTING OTHERS BEFORE THE ONSET OF ILLNESS.

38. 2. CONVALESCENT CARRIERS
FOLLOWING AN APPARENT DISEASE, GETS RECOVERY BUT CAN ABLE TO SPREAD DISEASE.
3.HEALTHY CARRIERS
THEY EMERGE FROM SUBCLINICAL CASES. THEY ARE VICTIMS OF SUBCLINICAL INFECTION WHO HAVE
DEVELOPED CARRIER STATE WITHOUT SUFFERING FROM DISEASE. BUT ARE A SHEDDING DISEASE
AGENT.
4.TEMPORARY CARRIERS
ARE THOSE WHO SHED THE INFECTIOUS AGENT FOR SHORT PERIODS OF TIME.
5.CHRONIC CARRIERS
ONE WHO EXCRETES THE INFECTIOUS AGENT FOR INDEFINITE PERIODS.
THE LONGER THE CARRIER STATE,THE GREATER THE RISK TO THE COMMUNITY.
EG; TYPHOID

39. 6.PORTAL OF EXIT
• THE MEDIUM THROUGH WHICH THE PATHOGEN OR INFECTIOUS AGENT ESCAPES FROM
THE RESERVOIR.
• IT INCLUDES; URINARY TRACT, INTESTINAL TRACT, RESPIRATORY TRACT AND OTHERS.
b. ANIMAL RESERVOIR
• IT IS ALSO A MAJOR SOURCE OF INFECTION.
• IT INCLUDES ANIMALS, BIRDS, RODENTS,ORTHOPODS (MOSQUITOES, FLIES, LICE, TICKS, MITE ETC)
c. ENVIRONMENTAL RESERVOIR
• IT INCLUDES SOIL, WATER,AIR, INANIMATE OBJECTS ETC.
• MAIN PORTAL OF EXIT INCLUDE: RESPIRATORY TRACT, GIT, URINARY TRACT ETC.

40. 2.MODE OF TRANSMISSION
TRANSMISSION OF AGENT OR ORGANISM
FROM THE RESERVOIR TO A NEW HOST IS THE
SECOND STEP IN THE CHAIN OF INFECTION.
 PORTAL OF ENTRY: MEDIUM BY WHICH
INFECTIOUS AGENT ENTERS TO A NEW
HOST.
 MODE OF TRANSMISSION IS CATEROGISED
INTO TWO:
•1.DIRECT TRANSMISSION
•2.IN-DIRECT TRANSMISSION

41. DIRECT
TRANSMISSION
1.DIRECT
CONTACT
2.DROPLET
INFECTION
3.CONTACT WITH
SOIL
4.INOCULATION
INTO SKIN OR
MUCOSA
5.TRANSPLACENTAL
OR VERTICAL
IN-DIRECT
TRANSMISSION
1.VEHICLE BORNE
2.VECTOR BORNE
a.MECHANICAL
b.BIOLOGICAL
3.AIR BORNE
a.DROPLET NUCLEI
b.DUST
4.FOMITE BORNE
5.UNCLEAN HANDS
AND FINGERS.

42. DIRECT TRANSMISSION
1.DIRECT CONTACT
 INFECTION MAY BE TRANSMITTED BY
DIRECT CONTACT FROM SKIN TO SKIN,
MUCOSA TO MUCOSA OR MUCOSA TO
SKIN OF SAME OR OTHER PERSON.
 EG: TOUCHING, KISSING, SEXUAL
INTERCOURSE.
 DISEASES TRANSMITTED INCLUDE STD
AND AIDS, LEPROSY, SKIN AND EYE
INFECTION.

43. 2.DROPLET INFECTION
DURING DIRECT PROJECTION OF A SPRAY OF DROPLETS OF
SALIVA AND NASOPHARYNGEAL SECRETIONS DURING
COUGHING, SNEEZING, SPEAKING OR SPITTING.
3.CONTACT WITH SOIL
INFECTIOUS AGENT PRESENT IN THE SOIL CAN CAUSE HOOK-
WORM,TETANUS ETC. WHEN HOST COMES IN CONTACT WITH
THE SOIL.

44. 4.INOCULATION INTO SKIN OR MUCOSA
 INFECTIOUS AGENT GET INOCULATED DIRECTLY INTO
THE SKIN OR MUCOSA.
 EG: RABIES VIRUS BY DOG BITE, HEP-B BY
CONTAMINATED SYRINGES AND NEEDLES.
5.TRANSPLACENTAL (VERTICAL)
 INFECTIOUS AGENT IS TRANSMITTED TRANSPLACENTALLY.
ANOTHER FORM OF DIRECT TRANSMISSION.
 EG: TORCH= TOXOPLASMA G0NDI,RUBELLA VIRUS,
CYTOMEGALO VIRUS, AND HERPES VIRUS.

45. IN-DIRECT TRANSMISSION
1.VEHICLE BORNE
 IT IMPLIES TRANSMISSION OF THE
INFECTIOUS AGENT THROUGH THE
AGENCY OF WATER, FOOD (INCLUDING
RAW VEGETABLES,FRUITS,MILK AND
MILK PRODUCTS), ICE,
BLOOD,SERUM,PLASMA ETC.
 EG: DIARRHEA, CHOLERA

46. 2.VECTOR BORNE
 IN EPIDEMIOLOGY, VECTOR IS DEFINED AS AN ARTHROPOD OR ANY LIVING CARRIER
(EG: SNAIL) THAT TRANSPORTS AN INFECTIOUS AGENT TO A SUSCEPTIBLE
INDIVIDUAL.
 TRANSMISSION BY A VECTOR MAY BE MECHANICAL OR BIOLOGICAL.

47. 3.AIR-BORNE
a. DROPLET NUCLEI
 THESE ARE A TYPE OF PARTICLES IMPLICATED IN THE SPREAD OF
AIRBORNE INFECTION.
 THEY ARE TINY PARTICLES (1-10 MICRONS) THAT REPRESENT THE
DRIED RESIDUE OF DROPLETS.
 THEY NOT ONLY KEEP FLOATING IN THE AIR BUT MAY BE
DISSEMINATED BY AIR CURRENTS FROM THE POINT OF ORIGIN.
 EG: TB, MEASLES, CHICKENPOX, COVID-19

48. b. DUST
 SOME OF THE LARGER DROPLETS WHICH
ARE EXPELLED DURING TALKING,
COUGHING, OR SNEEZING SETTLE DOWN
BY BY THEIR SHEER WEIGHT ON THE
FLOOR, CARPET, FURNITURE, CLOTHES,
BEDDING, LINEN AND OTHER OBJECTS IN
THE IMMEDIATE ENVIRONMENT AND
BECOME PART OF THE DUST.
 AIR BORNE DUST IS PRIMARILY INHALED
BUT MAY SETTLE ON UNCOVERED FOOD
AND MILK.

49. 4. FOMITE–BORNE
 THESE ARE INANIMATE ARTICLES OR SUBSTANCES
OTHER THAN WATER OR FOOD CONTAMINATED BY
THE INFECTIOUS DISCHARGES FROM A PATIENT AND
CAPABLE OF HARBOURING AND TRANSFERRING THE
INFECTIOUS AGENT TO A HEALTHY PERSON.
 FOMITES INCLUDE SOILED CLOTHES, TOWELS, LINEN,
HANDKERCHIEFS, CUPS, SPOONS, PENCILS, BOOKS,
TOYS, DRINKING GLASSES, DOOR HANDLE ETC
 DISEASES TRANSMITTED INCLUDE: DIPHTHERIA,
TYPHOID ETC

50. 5. UNCLEAN HANDS AND FINGERS
 HANDS ARE MOST COMMON MEDIUM BY WHICH
PATHOGENIC AGENTS ARE TRANSFERRED TO FOOD FROM THE
SKIN, NOSE, BOWEL ETC AS WELL AS FROM OTHER FOODS.
 TRANSMISSION TAKES PLACE BOTH DIRECTLY (HAND TO
MOUTH) AND INDIRECTLY.

51. 3.SUSCEPTIBLE HOST
• IT IS THE THIRD STEP OF DISEASE
TRANSMISSION.
• IT IS THE POSSIBLE VICTIM OF DISEASE OR
INFECTION.
Ie, THE INFECTIOUS AGENT GET
ENTERED INTO THE SUSCEPTIBLE HOST.
• AND MULTIPLICATION IN THE NEW HOST
COMPLETE THE CHAIN OF INFECTION.

52. THE HOST SUSCEPTIBILITY DEPENDS UPON THE
FOLLOWING CHARACTERISTICS;
1.ORGANISMS CHARACTERISTICS
 CAPACITY TO CAUSE DISEASE.
 NUMBER OF ORGANISMS INVADING THE HOST.
 VIRULENCE OF DISEASE.
2.HOST’S CHARACTERISTICS
 INDIVIDUAL’S IMMUNITY (NATURAL/ACQUIRED)
 DEMOGRAPHIC FEATURES (AGE,SEX,ETHNIC ORIGIN ETC)
 PSYCHOLOGICAL STATUS.
 SOCIAL FACTORS.

54. THANK YOU