Epidemiology Introduction

Changing Patterns of Community Health Health patterns in constant state of flux (الانماط الصحية في حالة تغير متواصل) Infectious versus chronic diseases (الامراض المعدية مقابل الامراض المزمنة) Population and age-related (السكان والعلاقة السنيه)

Chain of Infection Etiological agent Source/Reservoir Portal of exit Mode of transmission Portal of entry Susceptible host

Modes of Transmission Contact transmission Vehicle transmission Vector transmission

Classes of Epidemics Common source (vs. sporadic:متقطع) Point source Intermittent Continuous Propagated Your Assignment: Define these terms & identify which apply to the following three graphs

Disease Investigation Establish diagnosis Identify specific agent Describe according to person, place and time Identify source of agent Identify mode of transmission Identify susceptible populations

Epidemiology and Clinical Practice Clinical practice dependent on epidemiology Epidemiology defines natural history of disease Even descriptive information is useful

The Epidemiologic Approach Multistep process - First - determine association - Then prove causation(اثبات العلاقة السببية) - Not all associations are causal - Examine validity, false assumptions- e.g. - fluoride in water

Analytic Studies Type of study - Design - Analysis of data

Epidemiology and Prevention Identify high risk populations Modify risks Prevent exposures

Levels of Prevention Primary Secondary Tertiary

Levels of Prevention (cont’d) Primary Involves halting(وقف) any occurrence of a disease or disorder before it happens

Levels of Prevention (cont’d) Secondary Health screening and detection activities

Levels of Prevention (cont’d) Tertiary Retard(تأخير) or block the progression of condition

Yes may be invo… Common source – All victims acquire the infection from the same source (e.g. a contaminated water supply). Continuous source – Common source outbreak where the exposure occurs over multiple incubation periods Point source – Common source outbreak where the exposure occurs in less than one incubation period Propagated – Transmission occurs from person to person.