Download Lecture 1 Definition of epidemiology as a science

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.
Epidemiology – science about
mechanisms of epidemic process and
measures of it’s prevention and overcoming.
Epidemiological process – circulation
of infectious diseases among people
epizootological process – circulation of
infectious diseases among animals.
D. Samoilovich
(1724-1810)
D. K. Zabolotny
(1866-1929)
M. F. Hamalia
(1859-1949)
E. N. Pavlovsky
(1884-1965)
L. V.
Gromashevsky
(1887-1980)
Main motive forces
of epidemiological process:
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Source of infectious agent
Mechanisms of infectious agent transfer
Receptive organism
Secondary motive forces
of epidemiological process:
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Social factors
Environmental factors
Source of infectious agents
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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
PRINCIPLES OF EPIDEMIOLOGY
I principle
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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)
PRINCIPLES OF EPIDEMIOLOGY
II principle
Infectious agent’s localization in the organism
and mechanism of it’s 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.
Mechanism of infectious agent’s
transmission
1st phase: excretion of the causative agent
from the infected macroorganism
2nd phase: staining of the causative agent
in environment
3rd phase: infectious agent’s penetration
into healthy (susceptible) organism
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:
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intestinal infections
respiratory infections
blood infections
infections of external covers
PRINCIPLES OF EPIDEMIOLOGY
IV principle
Epidemic process originates and
maintained only due to combined
action of three main motive forces:
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Presence of infectious agent’s source;
Realization of transmission mechanism;
Population susceptibility to the infection.
If any of these factors is excluded,
epidemic process stop
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
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)
ANTIEPIDEMIC MEASURES IN
THE FOCUS OF INFECTION
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Measures concerning infectious agent’s 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
DEGREES OF INFECTION’S SPREADING:
1.
2.
3.
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.
PRINCIPLES OF INFECTIOUS DISEASES
CLASSIFICATION
(ACCORDING TO L. GROMASHEVSKY)
1.
2.
Localization of infectious agent
in organism
Mechanisms responsive for
transmission of infectious agent
GROUPS OF INFECTIOUS DISEASES
(according to Gromashevsky)
Intestinal infections – are transferred by fecaloral mechanism
2.
Respiratory infections – are transferred by the
droplet mechanism
3.
Blood infections – by means of transmissive
mechanism of transfer
4.
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
1.
Infectious agents, discovered during recent
25 years
Year
Micro organism
Disease
Acute leukemia of T-lymphocytes (ATL)
T-cell Tropical spastic affection (TSP)
Myelopathy, connected with HTLV-1 (HAM)
Leukemia
borreliosis (Laim’s disease)
HIV-infection/AIDS, AIDS-dementia
1980
HTLV-1
(human
lymphotropic virus)
1982
1982
1983
HTLV-2
Borrelia burgdorferi
HIV-1, HIV-2
1983
JC virus
Progressive multifocal leuko-encephalopathy
1983
Escherichia coli O157:H7
Enterohemorrhagic Escherichiosis, hemolyticuremic 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
Year
Micro organism
Disease
Nasopharyngitis, pneumonia, bronchial asthma,
angina pectoris, endocarditis.
1989
Chlamidia pneumoniae
1990
Herpes virus-7th type(HHV-7) Chronic fatigue syndrom
1990
Hepatitis E virus (HЕV)
Hepatitis E
1992
Vibrio cholerae O139:H7
Cholera
1992
Bartonella henselae
1993
Chlamidia pecorum
Benign lymphoreiculocytosis (disease of cat’s
scratches)
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
Year
Micro organism
Disease
1996
Prions
1997
Influenza virus A - H7N1
Prions diseases: Crointsfeldt-Jacob, Kuru,
Gerstman-Strausslar-Sheinker syndrome, fatal
family insomnia, Alpers disease, amyotrophic
leukospogiosis, myositis with prion-associative
inclusions
Influenza (Hong Kong)
1997
1997
1999
1999
1999
Hepatitis TT virus
Hepatitis TTV
Enterovirus -71st type
Nipag virus
Influenza virus A - H9N2
Hepatitis Sen virus
Severe acute respiratory
syndrome virus (SARS)
Epidemic meningitis
Meningitis and encephalitis
Influenza (Hong Kong)
Hepatitis SenV
2002
Severe acute respiratory syndrome
Epidemical
method of
investigation. Epidemic
diagnosis. Prevention of
Infectious Diseases &
Measures to Control
Them
Epidemiological methods
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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
Historic pandemics
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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.
Prevention & control
include:
Mass-scale measures aimed at improvement of
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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
Prophylaxis
Preventive
Antepidemic
The basic factors for
development of an
epidemic process:
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the source of infection;
transmission mechanism;
susceptibility of population
Control of infection source
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Timely revealing of sick persons. Active
detection is performed by medical
personnel at hospitals, polyclinics,
medical posts
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Isolation (in hospital, at home)
Treatment
Examination for the carrier
(sanation)
state
Disruption of infection
transmission pathways
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General sanitary measures
(community hygiene)
Health education of population
Disinfection
Sterilization
Disinsection
Deratization
Disinfection
Focal
Current
Preventive
Final
Preventive disinfection
Mechanical
Biological
Chemical
Chlorine-,
oxygencontaining
substances,
Phenols,
Acids,
Alkalis,
hydrogen
peroxide,
formaldehyde
Physical
Boiling,
Steam, UV
radiation &
others
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.
Disinsection
Destroying
Mechanical
Physical
Biological
Chemical
Genetic
Preventive
Deratization
(rodent control)
Destroying
Mechanical
Biologycal
Chemical
Preventive
Quarantine measures
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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)
Measures to increase
opportunity
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Specific – preventive vaccinations,
immune globulins, serums
Non-specific – improving of living and
labour conditions, nutrition, physical
training
Contraindications to
prophylactic vaccination
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Acute fever
Recently sustained infections
Chronic diseases
Second half of pregnancy, first nursing
period
Allergic diseases and states
Oncology pathology
Antepidemic measures in the
focus
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Examination by epidemiologist or a
rural physician
Final desinfection
Taking of material for microbiologic
investigation
Observation during the incubation
period
Health education of population