Presentation on theme: "Prof. Saman Wimalasundera"— Presentation transcript:
1 Prof. Saman Wimalasundera MBBS DO PhDProfessor in Community MedicineFormer Head, Department of Community MedicineIn charge OphthalmologistCommunity Ophthalmology centerFaculty of MedicineUniversity of RuhunaGalleSri Lanka
3 The concepts of epidemiology were first suggested by Hippocrates in the fifth centuryB.C. that the development of human diseasemight be related to external and personnelenvironment of an individual.
4 The word epidemiology is derived from Greek and means “Studies upon people”Epi – Upon, Demos – People, Logia – StudyIn contrast to clinical medicine epidemiologyinvolves the study of group of people ratherthan individuals.
5 Epidemiologist vs. clinician A clinician identifies the ailment in his patientsusing certain scientifically developed tools toascertain history of illness, clinical examinationand investigations.Epidemiologist addresses the understandingof the distribution and determinants of adisease in a community (not an individual)using standard parameters.
6 What constitute epidemiology Epidemiology includes:-1. The methods for measuring the health ofgroups and determining the attributesand exposures that influence health.2. The study of the occurrence of disease in its natural habitat rather than in the controlled environment of the laboratory.
7 3. The methods for the quantitative study of the distribution, variation, and determinantsof health related outcomes in specificgroups (sub populations) of individuals, andthe application of this study to thediagnosis, treatment, and prevention ofdisease status or events.
8 Evolution of epidemiology The evolution of medical sciences in itsearlier phase was based on curativemedicine. The primary objective was to curea patient of his illness. Doctors in historicaltimes looked at their patients as ill peoplewho needed some treatment.
9 Thus medical science was individual oriented. But gradually it became evidentthat better human health could be achievedby prevention of diseases rather than bycure.
10 A Historical Sketch A Long sketch of time ran for more than 2 millennia from Hippocrates ( B.C.) tothe first third of 19th century.Hippocrates developed the medicalapproach by providing concise, accurate andcomplete description of actual clinical cases.
11 An Italian clinician called Bernardino Ramazzini in 1700 moved from observation ofclinical cases to the consideration of ‘workcircumstances’ in similar cases. He is nowregarded as the founder of occupationalmedicine. (Explained in his book. “De MorbisArtificum Diatriba”).
12 The major step forward in epidemiology occurred in 1662 The major step forward in epidemiology occurred in John Graunt analyzed the weekly reports of births and deaths in London.For the first time in the history, a quantified pattern of disease, deaths and births was Found. John Graunt is regarded as the founder of demography now.His observations were published in hisbook. Named “ the nature and politicalobservations made upon the bills of Mortality”.
13 After two centuries William Farr (1839) a physician was given the responsibility formedical statistics in England and Wales. Heset up a system for routine compilation of vitalstatistics and application of data for evaluationof deaths.
14 Hippocrates, Ramzinni, Graunt and Farr contributed to the understanding of diseasefrequency and distribution.Another British physician John Snowformulated and tested a hypothesis concerningthe origins of an epidemic of cholera in Londonon the basis of available descriptive data.
15 Snow postulated that cholera was transmitted by contaminated water. (thenunknown mechanism)He observed that death rates from Cholera were particularly high in certain areas of London.Those areas were supplied with waterby two water companies namely “Lambeth”and “Southwark & Vauxhall” in Both thecompanies that time drew water from riverThemes at a point heavily polluted with sewage.
16 The Lambeth company then changed its source to an area of Themes where the waterwas quite free from sewage of London.The rate of cholera deaths then declined inthose areas suppied by Lambeth company.
17 Death rates from cholera According to water company supplying sub districts of London Population in 1851Cholera deaths inDeaths per 100,000 livingSouthwark and VauxhallBoth companiesLambeth167, 654301, 14914, 6321921820011460
18 Concepts of epidemiology Definitions“Epidemiology is defined as the study of thedistribution and determinants of health relatedstatus or events in specified populations andthe application of this study to control the healthproblems” (Last 1988)
19 Applications of epidemiology The epidemiology is useful in:1. Search of cause/causes of disease/diseases.2. Helps to describe the health status ofpopulation or groups.3. Helps to discover and bridge gaps innatural history of diseases.
20 4. Helps in controlling the diseases. To break the weakest link in chain of transmission ofcommunicable diseases and reducing noncommunicable diseases.5. Helps in planning of health programs onevidence basis and setting up of healthpriorities.6. Helps to evaluate health programs andinterventions.
21 7. Helps to determine the chances or probability of occurrence of disease/deaths and disability8. Helps in better management of healthservices and hospital services.9. Helps to set-up cut-off levels betweennormal and abnormal population andestablish trigger levels for action orintervention.
22 Sources of epidemiological Measurements 1. Cross sectional surveys2. Medical records3. Death certificate4. Census5. Organizational data
23 Domains of epidemiology Descriptive epidemiologyDescriptive epidemiology is the most Basic form of epidemiology. It is concerned with the description of the patterns of occurrence of health-related status or events in groups.The determination of frequency and distribution of disease, incidence, prevalence, and mortality rates are included in descriptive epidemiology.
24 Analytical epidemiology Analytical epidemiology is based on theobservations made in the descriptiveepidemiology. The design, execution andanalysis of subjects between groups helpsevaluate potential association between riskfactors and health outcomes to answer thequestion “why?”.
25 Analytical epidemiology consists of two types of research processes 1. Observational process2. Experimental studies
26 Basic triads of descriptive and analytical epidemiology There are two different triads (3 essentialcomponents) considered in studying differentsections
28 Triad of descriptive epidemiology TimeChanging or stableSeasonal variationsSecular trends (long-term study ofincidence)Point source or propagatedCyclical variations (spikes ofincidences at regular intervals)
29 Triad of descriptive epidemiology PlaceGeographically restricted or widespreadRelation to water and food supplyMultiple cluster involvement or oneRural/Urban distribution
30 Triad of descriptive epidemiology PersonAgeSocio economic statusGenderEthnicity / RaceBehavior
31 Triad of analytical epidemiology AgentNutrientsPoisonsAllergensRadiationPhysical traumaMicrobesPsychological factors
32 Triad of analytical epidemiology Host factorsGenetic factorsImmunologic stateAgePersonal behavior
33 Triad of analytical epidemiology EnvironmentOvercrowdingAtmospheric changesModes of transmissionVectorVehicleReservoir
34 This forms the basis of clinical epidemiology. When periodic observations are made overa long period of time in patients with a widespectrum of clinical manifestations of thedisease, a complete profile of the naturalhistory of the disease may be obtained.This forms the basis of clinical epidemiology.
35 Epidemiology of diseases Sri Lanka is said to be facing a doubledisease burden due to communicable and noncommunicable diseases (NCD) today.What is triple burden???
36 The diseases burden in the country is given in terms of (apart from basic measures)1.Years of potential life lost2.Life expectancy free from disability3. Disability adjusted life years lost – DALYs4.Quality adjusted life years lost - QUALYsloss per 1000 population.Country has to fight to control communicableand non communicable diseases.
37 Epidemiology of communicable diseases (CCD) Definition :- Communicable diseaseA communicable or infectious disease is anillness caused by transmission of a specificinfectious agent or its toxic products from aninfected person or animal to a susceptiblehost, either directly or indirectly through anintermediate animal host, vector or inanimateenvironment (Last 1995)
39 What is an Epidemic? It is the occurrence of cases of illness, specific health related behavior or otherhealth related events clearly in excess ofnormal expectancy in a community or region.
40 An Endemic disease A disease that usually present in a population or given area at a relatively highprevalence and incidence rates in comparedto other areas.E.g. Malaria is an endemic disease inPolonnaruwa
41 Major emerging and re-emerging infectious diseases 1. HIV/AIDS2. Hepatitis B and Hepatitis C3. Tuberculosis4. Dengue5. Malaria6. Japanese encephalitis7. Plague8. Cholera
42 Major reasons for emergence of infectious diseases High population growth, uncontrolled andunplanned urbanization,Poor environmental sanitation,Migration of population,Natural disasters,Growing international trade, tourism and rapid travel,Alterations in microorganisms,Resistance to antimicrobials,Insecticide resistance,Weak public health system.Illiteracy and ignorance.
43 Chain of infection or chain of transmission Infectious agentTransmission processHostENVIRONMENTS
45 Transmission process This is the second important link in the chain of infection.Transmission is defined as “Spread ofinfectious agent through the environment or toanother person, from the reservoir andsource”.
47 Direct methods of transmission TouchingKissingSexual intercourseChild birthBreast-feedingAir borne, short distance via droplets(by coughing, Laughing, sneezing, spitting).Transfusion of bloodTransplacental from mother to fetus
48 Indirect transmission Vehicle borne transmission (bycontaminated food and water)Vector borne transmissionParenteral by unsafe injectionFomite transmissionUnclean hands
49 Control of communicable diseases (CCD)-discuss under 5 headings 1. Control of infectious agents in the environments2. Control of infectious agent in host3. Control of outbreaks of CCD4. Other measures5. Specific measures for control of HIV epidemic
50 (1) Control of infectious agents in the environments Controlling sources of infection1. Supply of safe drinking water by treatment and chlorination of water, pasteurization of milk.Safe disposal of human excreta and animal excreta by sewerage system and sanitary latrines, compost pits/manure pits.3. Control vectors of diseases – by source reduction and anti-larval and anti-adult measures.4. Animals – vaccinate dogs against rabies and eliminate street dogs.5. Rodent control measures-trapping and killing6. Hospital waste management7. Disinfections
51 (2) Control of infectious agent in host 1. Reservoir control2. Practice of chemoprophylaxis3. Surveillance4. Notification5. Quarantine1. Complete quarantine2. Modified quarantine6. Isolation7. Education and behavior
52 Control of outbreaks of CCD-different steps will be discussed later Communicable diseases like Malaria,JE, DHF , Hepatitis E & A, Hepatitis B andDiarrhoeal diseases quite often occur inepidemic proportion. Many local and focaloutbreaks are being reported quite frequently;Hence, control of outbreaks of these diseasesis an essential requirement.
53 (4) Other measures 1. Legislation Epidemic disease control act. And notification helps control of CCD.2. Observe international healthregulations
60 Epidemiology of non-communicable diseases (NCD) Non communicable diseases cover widerange of heterogeneous conditions affectingdifferent organs and systems of differentsocioeconomic groups.Over the last two decades morbidity andmortality due to cardiovascular diseases,mental disorders, cancer and trauma havebeen rising due to following causes.
61 Causes 1. Rise in life expectancy and increasing number of senior citizens.2. Changing life styles: Faulty diet, use ofalcohol, sedentary life-physical inactivityand rising stress-leading to obesity andstress related problems.
62 3. Exposure to environmental risk factors-air pollution.4. Use of tobacco5. Increasing population and rise inautomobiles and trauma incidence.
63 Implications In view of the chronic morbidity and high cost involve in the management of non-communicable diseases attention need to befocused on prevention, early detection andappropriate management. Further, thesediseases cause lot of disability anddependency and disease burden.
64 Multi - factorial origin Causes of NCD are multi-factorial. Rangeof life styles: risk taking behavior, changingdietary pattern, physical inactivity, use ofalcohol and tobacco and stress in life havebeen incriminated.
65 Future For non-communicable diseases throughout the all levels of care so as to reduce morbidityand mortality.
66 1. Well-structured information education and communication for primary and secondaryprevention of NCD.2. Reorientation and skill up gradation ofhealth care providers
67 3. Establishment of Referral linkages between primary secondary and tertiary institution.4. Production and provision of drugs for NCD.5. Development of institution for rehabilitationof disabled persons due to NCD, teachingpersons to live with their disability.
68 6. Development of hospices for terminally ill people who cannot have home based care.7. Creation of epidemiological database onNCD especially, CVD’s, strokes anddiabetes.