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Definition of epidemiology as a science. Epidemic process as a subject of studing of

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Title: Definition of epidemiology as a science. Epidemic process as a subject of studing of


1
Definition of epidemiology as a science. Epidemic
process as a subject of studing of  epidemiology
and his main driving forces. Classification of
infectious diseases. Epidemic method of 
infectious and not infectious morbidity research.
Directions of struggle with infectious diseases
and their preventive maintenance.
2
  • Epidemiology science about mechanisms of
    epidemic process and measures of its
    prevention and overcoming.
  • Epidemiological process circulation of
    infectious diseases among people epizootological
    process circulation of infectious diseases
    among animals.

3
D. Samoilovich (1724-1810)
4
D. K. Zabolotny (1866-1929)
5
M. F. Hamalia (1859-1949)
6
E. N. Pavlovsky (1884-1965)
7
L. V. Gromashevsky (1887-1980)
8
Main motive forces of epidemiological process
  • Source of infectious agent
  • Mechanisms of infectious agent transfer
  • Receptive organism
  • Secondary motive forces
  • of epidemiological process
  • Social factors
  • Environmental factors

9
Source of infectious agents
  • Human patient or carrier (from the end of the
    incubation period prodromal period period of
    acute illness convalescence, when microorganism
    excretion occur) - antroponosis
  • Animals (domestic, wild) zoonosis
  • Environment - sapronosis

10
PRINCIPLES OF EPIDEMIOLOGY
  • I principle
  • Source of infectious agent is infected (sick or
    carrier) organism - human or animal
  • (object which is the site of natural
    habitation and multiplication of pathogenic
    organisms, from where they can infect healthy
    people)

11
PRINCIPLES OF EPIDEMIOLOGY
  • II principle
  • Infectious agents localization in the organism
    and mechanism of its transmission from one
    individual to another form persistent connection,
    which provide pathogenic species preservation in
    the environment and continuity of epidemic
    process of infectious disease.

12
Mechanism of infectious agents transmission
  • 1st phase excretion of the causative agent from
    the infected macroorganism
  • 2nd phase staining of the causative agent in
    environment
  • 3rd phase infectious agents penetration into
    healthy (susceptible) organism

13
PRINCIPLES OF EPIDEMIOLOGY
  • III principle
  • Infectious diseases can be rationally classified
    according to specific localization of infectious
    agent in the organism, corresponding mechanism of
    transmission and main biological properties of
    causative agent
  • intestinal infections
  • respiratory infections
  • blood infections
  • infections of external covers

14
PRINCIPLES OF EPIDEMIOLOGY
  • IV principle
  • Epidemic process originates and maintained only
    due to combined action of three main motive
    forces
  • Presence of infectious agents source
  • Realization of transmission mechanism
  • Population susceptibility to the infection.
  • If any of these factors is excluded, epidemic
    process stop

15
PRINCIPLES OF EPIDEMIOLOGY
  • V principle
  • Natural and social factors stipulate
    quantitative and qualitative changes in the
    epidemic process (increase or decrease), thus
    they are
  • secondary motive forces
  • of epidemic process

16
EPIDEMICAL FOCUS
  • site of infectious agent habituation, including
    surrounding territory with the limits where it
    can be contagious for others.
  • Epidemical focus exist in time (maximal
    incubation period of the disease) and in area
    (determined by transmission mechanism)

17
ANTIEPIDEMIC MEASURES IN THE FOCUS OF INFECTION
  • Measures concerning infectious agents source
  • Disease diagnosis
  • Registration
  • Isolation of the patient (carrier)
  • Etiological treatment
  • Measures concerning transmission mechanisms
  • disinfection (disinsection, deratization)
    current, final
  • Measures concerning contact persons
  • Sanitary processing
  • Medical observation
  • Laboratory examination
  • Specific prophylaxis

18
DEGREES OF INFECTIONS SPREADING
  • Sporadic normal level of morbidity for the
    given territory in a given period of time
  • Epidemic morbidity in a few times more higher
    than sporadic
  • Pandemic extraordinary intensive epidemic
    process and considerably greater than epidemic.
  • Endemic infections connected to certain
    territory.
  • Exotic infections diseases, which are not
    characteristic for the local territory, but can
    be transferred from other countries.

19
PRINCIPLES OF INFECTIOUS DISEASES
CLASSIFICATION (ACCORDING TO L. GROMASHEVSKY)
  1. Localization of infectious agent in organism
  2. Mechanisms responsive for transmission of
    infectious agent

20
GROUPS OF INFECTIOUS DISEASES (according to
Gromashevsky)
  • Intestinal infections are transferred by
    fecal-oral mechanism
  • Respiratory infections are transferred by the
    droplet mechanism
  • Blood infections by means of transmissive
    mechanism of transfer
  • Infections of external covers by means of
    contact or contact-wound mechanism
  • Distinguished trans-placental (vertical)
    mechanism of transfer, and accordingly,
    infections which are transferred by
    trans-placental way

21
Infectious agents, discovered during recent 25
years
Year Micro organism Disease
1980 HTLV-1 (human T-cell lymphotropic virus) Acute leukemia of T-lymphocytes (ATL) Tropical spastic affection (TSP) Myelopathy, connected with HTLV-1 (HAM)
1982 HTLV-2 Leukemia
1982 Borrelia burgdorferi borreliosis (Laims disease)
1983 HIV-1, HIV-2 HIV-infection/AIDS, AIDS-dementia
1983 JC virus Progressive multifocal leuko-encephalopathy
1983 Escherichia coli O157H7 Enterohemorrhagic Escherichiosis, hemolytic-uremic syndrome
1983 Helicobacter pylori Gastrodeudenitis
1986 Herpes virus-6h type (HHV-6) Sudden exanthema (three-day fever)
1989 Ehrlichia spp. Ehrlichiosis
1989 Hepatitis C virus (HCV) Hepatitis C
22
Year Micro organism Disease
1989 Chlamidia pneumoniae Nasopharyngitis, pneumonia, bronchial asthma, angina pectoris, endocarditis.
1990 Herpes virus-7th type(HHV-7) Chronic fatigue syndrom
1990 Hepatitis E virus (H?V) Hepatitis E
1992 Vibrio cholerae O139H7 Cholera
1992 Bartonella henselae Benign lymphoreiculocytosis (disease of cats scratches)
1993 Chlamidia pecorum Nasopharyngitis, pneumonia, bronchial asthma, angina pectoris, endocarditis.
1993 Sin Nombre virus Gantaviral pulmonary complex
1994 Sabia virus Brazilian hemorrhagic fever
1994 Herpes virus 8th type(HHV-8) Sarcoma Kaposi
1994 Gendra virus Meningitis and encephalitis
1995 Hepatitis G virus Hepatitis G
23
Year Micro organism Disease
1996 Prions Prions diseases Crointsfeldt-Jacob, Kuru, Gerstman-Strausslar-Sheinker syndrome, fatal family insomnia, Alpers disease, amyotrophic leukospogiosis, myositis with prion-associative inclusions
1997 Influenza virus A - H7N1 Influenza (Hong Kong)
1997 Hepatitis TT virus Hepatitis TTV
1997 Enterovirus -71st type Epidemic meningitis
1999 Nipag virus Meningitis and encephalitis
1999 Influenza virus A - H9N2 Influenza (Hong Kong)
1999 Hepatitis Sen virus Hepatitis SenV
2002 Severe acute respiratory syndrome virus (SARS) Severe acute respiratory syndrome




24
  • Epidemical method of investigation. Epidemic
    diagnosis. Prevention of Infectious Diseases
    Measures to Control Them

25
Epidemiological methods
  • Observation studying of the focus
  • Inspection revealing of the source
  • Examination studying of morbidity
  • Analysis of morbidity
  • Experiment microbiological and serological
    examination, physical and chemical studies,
    experiment on humans and animals

26
Historic pandemics
  • Plague of Justinian, from 541 to 750, killed
    between 50 and 60 of Europe's population.
  • The Black Death of 1347 to 1352 killed 25 million
    in Europe over 5 years (estimated to be between
    25 and 50 of the populations of Europe, Asia,
    and Africa - the world population at the time was
    500 million).
  • The introduction of smallpox, measles, and typhus
    to the areas of Central and South America by
    European explorers during the 15th and 16th
    centuries caused pandemics among the native
    inhabitants. Between 1518 and 1568 disease
    pandemics are said to have caused the population
    of Mexico to fall from 20 million to 3 million.
  • The first European influenza epidemic occurred
    between 1556 and 1560, with an estimated
    mortality rate of 20.
  • Smallpox killed an estimated 60 million Europeans
    during the 18th century (approximately 400,000
    per year). Up to 30 of those infected, including
    80 of the children under 5 years of age, died
    from the disease, and one third of the survivors
    went blind.
  • In the 19th century, tuberculosis killed an
    estimated one-quarter of the adult population of
    Europe by 1918 one in six deaths in France were
    still caused by TB.
  • The Influenza Pandemic of 1918 (or the Spanish
    Flu) killed 25-50 million people (about 2 of
    world population of 1.7 billion). Today Influenza
    kills about 250,000 to 500,000 worldwide each
    year.

27
Prevention control include
  • Mass-scale measures aimed at improvement of
    public health, prevention of infectious diseases
    spreading
  • Medical measures aimed at reduction of infectious
    morbidity eradication of some diseases
  • Health education involvement of population in
    prevention or restriction of infectious diseases
    spreading
  • Prevention of infectious diseases importing from
    other countries

28
Prophylaxis
Preventive
Ant- epidemic
29
The basic factors for development of an epidemic
process
  • the source of infection
  • transmission mechanism
  • susceptibility of population

30
Control of infection source
  • Timely revealing of sick persons. Active
    detection is performed by medical personnel at
    hospitals, polyclinics, medical posts
  • Isolation (in hospital, at home)
  • Treatment
  • Examination for the carrier state (sanation)

31
Disruption of infection transmission pathways
  • General sanitary measures (community hygiene)
  • Health education of population
  • Disinfection
  • Sterilization
  • Disinsection
  • Deratization

32
Disinfection
Preventive
Focal
Current
Final
33
Preventive disinfection
Chemical
Physical
Mechanical
Chlorine-, oxygen- containing substances, Phenols
, Acids, Alkalis, hydrogen peroxide, formaldehyd
e
Boiling, Steam, UV radiation others
Biological
34
Sterilization
  • complete eradication of pathogenic and
    non-pathogenic microorganisms (spores included)
    in the environment. Sterilization is used for
    surgical, gynaecological, stomatological and
    other tools, dressing materials, linen, needles,
    syringes, etc. Nutrient media, laboratory ware,
    tools and instruments are sterilized in
    microbiology.

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Disinsection
Destroying
Preventive
Mechanical Physical Biological
Chemical Genetic
43
Deratization (rodent control)
Destroying
Preventive
Mechanical Biologycal Chemical
44
Quarantine measures
  • medical examination of persons who arrive into
    or depart from a given country, their vehicles
    belongings
  • availability of special medical documentation
    (international certificate of vaccination,
    certificate of deratization the like) must be
    checked
  • revealing isolation of persons with infectious
    diseases, and isolation of persons who require
    medical observation
  • disinfection, disinsection, deratization of
    means of transportation, of cargo luggage (for
    specisl indications)

45
Measures to increase opportunity
  • Specific preventive vaccinations, immune
    globulins, serums
  • Non-specific improving of living and labour
    conditions, nutrition, physical training

46
Contraindications to prophylactic vaccination
  • Acute fever
  • Recently sustained infections
  • Chronic diseases
  • Second half of pregnancy, first nursing period
  • Allergic diseases and states
  • Oncology pathology

47
Antepidemic measures in the focus
  • Examination by epidemiologist or a rural
    physician
  • Final desinfection
  • Taking of material for microbiologic
    investigation
  • Observation during the incubation period
  • Health education of population
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