Definition of epidemiology as a science Epidemic process

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: n n n Source of infectious agent Mechanisms of infectious agent transfer Receptive organism Secondary motive forces of epidemiological process: n n Social factors Environmental factors

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 n Animals (domestic, wild) – zoonosis n Environment - sapronosis n

PRINCIPLES OF EPIDEMIOLOGY I principle n 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 1 st phase: excretion of the causative agent from the infected macroorganism 2 nd phase: staining of the causative agent in environment 3 rd 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: § § intestinal infections respiratory infections blood infections of external covers

PRINCIPLES OF EPIDEMIOLOGY IV principle Epidemic process originates and maintained only due to combined action of three main motive forces: n n n 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 q § § § § 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 1983 Acute leukemia of T-lymphocytes (ATL) HTLV-1 (human T-cell Tropical spastic affection (TSP) lymphotropic virus) Myelopathy, connected with HTLV-1 (HAM) HTLV-2 Leukemia Borrelia burgdorferi borreliosis (Laim’s disease) HIV-1, HIV-2 HIV-infection/AIDS, AIDS-dementia Progressive multifocal leuko. JC virus encephalopathy Escherichia coli Enterohemorrhagic Escherichiosis, O 157: H 7 hemolytic-uremic syndrome 1983 Helicobacter pylori 1986 Herpes virus-6 h (HHV-6) 1989 Ehrlichia spp. Ehrlichiosis Hepatitis C virus (HCV) Hepatitis C 1980 1982 1983 Gastrodeudenitis type Sudden exanthema (three-day fever)

Yea Micro organism r Disease Nasopharyngitis, pneumonia, bronchial 1989 Chlamidia pneumoniae asthma, angina pectoris, endocarditis. Herpes virus-7 th Chronic fatigue syndrom 1990 type(HHV-7) 1990 Hepatitis E virus (HЕV) Hepatitis E cholerae Cholera 1992 Vibrio O 139: H 7 Benign lymphoreiculocytosis (disease of 1992 Bartonella henselae cat’s scratches) Nasopharyngitis, pneumonia, bronchial 1993 Chlamidia pecorum asthma, angina pectoris, endocarditis. 1993 Sin Nombre virus Gantaviral pulmonary complex 1994 Sabia virus Brazilian hemorrhagic fever virus 1994 Herpes 8) type(HHV 1994 Gendra virus 8 th Sarcoma Kaposi Meningitis and encephalitis

Yea Micro organism r Prions diseases: Crointsfeldt-Jacob, Kuru, Gerstman-Strausslar-Sheinker syndrome, fatal family insomnia, Alpers disease, amyotrophic leukospogiosis, myositis with prion-associative inclusions 1996 Prions Influenza virus A 1997 H 7 N 1 1997 Hepatitis TT virus Disease - Influenza (Hong Kong) 1997 Enterovirus -71 st type 1999 Nipag virus 1999 Influenza virus A H 9 N 2 1999 Hepatitis Sen virus Severe acute 2002 respiratory syndrome virus (SARS) Hepatitis TTV Epidemic meningitis Meningitis and encephalitis Influenza (Hong Kong) Hepatitis Sen. V Severe acute respiratory syndrome

n. Epidemical method of investigation. Epidemic diagnosis. Prevention of Infectious Diseases & Measures to Control Them

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

Historic pandemics n n n n 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 15 th and 16 th 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 18 th 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 19 th 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 n n 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: n n n the source of infection; transmission mechanism; susceptibility of population

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

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

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 n n 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 Specific – preventive vaccinations, immune globulins, serums n Non-specific – improving of living and labour conditions, nutrition, physical training n

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

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