GENERAL EPIDEMIOLOGY

Dr. Amany R.AboEL-Seoud

Prof. of Community Medicine

Zagazig University, EGYPT

INFECTIOUS CYCLE

agent

exit

Mode of transmiss

ioninlet

host

AGENT

bacteria virus

parasite rickettsia

Protozoa& fungi

CASES

CARRIERS

SOIL

ANIMAL

RESERVOIRSOURSE

CASES

CARRIERS

Timing period exit

ANIMALS & SOIL

MODE OF TRANSMISSION DROPLET \air borne

FOOD BORNE INFECTIONS

CONTACT INFECTIONS

ARTHROPOD INFECTIONS

CONGENITAL TRANSMISSION

WHEN INFECTION OCCURS?

EcologyEpidemiological triad

Host

Agent

Environment

HOST FACTORS Age, sex, pregnancy, occupation, education Nutrition Socioeconomic status Level of immunity: types of immunity: Inherited & acquired (natural ,

artificial)

AGENT Number Virulance Pathogenicity

ENVIRONMENT Sanitation of air Sanitation of water Sanitation of housing Sanitation of food Sanitation of waste disposal Sanitation of animals, rodents control

TYPES OF SPREAD OF INFECTIONS Sporadic Outbreak Epidemic: common source / propagated Pandemic Endemic Epizootic

METHODS OF PREVENTION OF INFECTIOUS DISEASE AIM AT:

Eradication of infectious diseases Elimination or control of reservoir of

infection (man, animal, soil) Interruption of mode of transmission

(sanitary environment) Protection of susceptible host

(immunization) 

PREVENTION OF COMMUNICABLE DISEASES

Primary prevention: to prevent the occurrence of infection (called also general prevention).

Secondary prevention: to prevent the spread of infection to others, to prevent the complications among cases (may be called specific prevention or control measures).

Tertiary prevention: to prevent further deterioration of cases, to help complicated cases to cope with their handicapped conditions.

EMERGING/ RE-EMERGING OF INFECTIOUS DISEASE Population growth and demographic changes Increased travel Global climatic change Wars, famines and disasters affecting many parts

of the world Abuse of drugs and antibiotics Microbial adaptation and mutations Bioterrorism Increased nursing homes, old age institutions Deforest and changing natural areas Building dams, changing irrigation systems Unequal distribution of health services, vaccines,

drugs etc

Examples of emerging infections: SARS Anthrax Hantavirus Arenaviruses Swine influenza Ebola virus Examples of reemerging infections: Tuberculosis Malaria AIDS

CLASSIFICATION OF INFECTIOUS DISEASES Air borne Food borne Contact/ blood borne Arthropod borne congenital