The word “epidemiology” has been used since when most of infection diseases were epidemic

1. Today: The concept of “epidemiology” includes the study of objective laws of etiology, distribution and control of infection diseases in a human community and also elaboration of methods to prevent and control these diseases.

2. Definition of the term “epidemiology” was formulated at the “Iternational Symposium of epidemiologists” in Prague (1960:

3. “Epidemiology is independent branch of medicine in a human community and is aimed at prevention, control and final eradication of these diseases”

The subject Matter of Epidemiology

Special epidemiology studies epidemiologic characteristics of each particular infection diseases and the methods to prevent and control it.

General epidemiology studies the law of distribution of infection diseases among people (characteristics of sources of infection, the mechanism of transmission, Susceptibility to infection diseases and the like) and the general principles of prevention and control of these diseases

History of Epidemiology

The numerous epidemics of black plague, smallpox and typhus in the 14-15th centures aroused such suspicions in physicians Fracastorius, an Italian physician (1483-1553)

Produceda theory that proved contagiosity of these diseases

In Russia of the 11th centure they isolated people with contagiosus diseases and burried the dead separately from the others.

First quarantines were organized in 16th centure patients where separated from their

relativers, and funeral services over the dead were forbidden.

History of Epidemiology

In the 18 th centure Edward Jenner (English physician, 1749-1823) devised a safe and effective method of preventive natural smallpox by inoculating people with cowpox vaccine.

At about the same time The Russian epidemiologist \D Samoilovich (1744-1805) vas among The first who attempt to discover microscopically the causative factor of plague in exrementers and various tissues of diseased.

He organized quarantines At the Black Sea coastal area and become world famous for his work in epidemiology.

The scientific discoveries made by Paster, Koch, Mechnicov, Ivanovsky, promoted the study of aetiology, Pathogenesis, course of infection disease and also their Epidemiology

History of Epidemiology

Minch 91836-1896) +Mochutcovsky

Inoculated themselves with a blood of patirnt with reccurent fever and Typhoid fever. They proved by their experiments that the diseases could be tansmitted by blood-sucking insects.

Gabrichevsky (1860-1907) made an important contribution to the study of diphteria (serotherapy), Scarlet fever (etiology, manufacture of vaccines and vaccinatin, Epidemiology of malaria etc.

History of Epidemiology

Zabolotny (1866-1929) is the founder of Soviet Epidemiology. He is The other of “Fundamentals of Epidemiology”.

Sysin, Semashko, Soloviev, Bashenin and Martshinovsky worked much to create anti-epidemic cervice.

Pavlovsky developed the theory of natural nidality of some infection diseases. Soviet epidemiologists are the first and the second laws of sourses of infection and the teaching of epidemic process.

ACCORDING TO THE LOW any lnfected person or animal cfn be the sourse of infection.

ACCORDING TO THE second LOW there exist agreement between location of the causative microorganism in a macroorganism fnd mechanism of infection.

The theory of epidemic process

process developes only througt interaction between the sourses of infection, the specific mechanism of transmission and susceptibility of population which respect to a given disease

An infection process is the interaction of a pathogenic microorganism with a macroorganism under certain social and environmental condition. mechanism of infection.

The consept of infection disease

The condition manifested by a disease state of a patient and so called carrier state

The condition of developing infection process:

1. The specific propertics of infection agent

2. Various pathogenicity

3. Virulence of this agent

4. The quantity of microorganism that enter the macroorganism

5. Resistanse of macroorganism

6. Duration of specific immunity account for the multitude of clinical manifestation of infection

infection can be clinically pronounced or it may be asymptomatic

A clinically manifest infection can run a typical or atypical course.

A clinically manifest infection disease is usually classed as mild, Moderate, and severe: according to the duration

the disease can be acute or chronic.

An acute infection (smallpox, measles, plague) is characterized by a shot stay of the causative agent in the body and development of specific immunity in the patient towards the given infection

A chronic infection (Brucellosis, Tuberculosis) can last for years

Asymptomatic infection can be subclinical and latent.

A person with subclinical infection (acute or chronic) looks in full health. Fnd a disease can be diagnosed by detecting the causative agents, specific antibodies, and functional and morphological changes in the organs and tissue that are specific for a given disease.

Such patients ( or carriers) are special danger for the surrounding people since they are the source of infection

Latent or persistant forms of human or animal infection

At the same time a repeated subclinical infection in Poliomielitis, Diphtheria, influenza promotes formation of an immune group of people (herd immunity).

Acute or chronic subclinical forms (carriers states) are more common in Typhoid fever A and B, Sallmonellesis, Viral hepatitidis.

Latent or persistent forms of human and animal infection are a prolonged asymptomatic interaction of macroorganism with the pathogenic agents which are present in modified (defective) forms.

There are defective interfering particles in latent viral infection and L-forms, spheroplastsin bacterial infection.

Being inside the host cell these forms survives for long periods of time and there are not released into the environment.

Under the action various provoking factors (such as thermal effects, injuries, physic trauma, transplantation, blood transfusion, various disease states) persistant infection can be activated and become clinically manifest.

The microbe regains its pathogenic properties.

Threre are famous L-forms of streptococci streptococci streptococci

Cholera vibrio, Bacillus diphtheria, Typhoid fever, tetanus

Protosoa and rickettsia

Protosoa and rickettsia can also persist. Latent epidemic recrudescent typhus is manifested by relapses of epidemic recrudescent typhus (Brills

Disease)