Modifiable Risk

Lifestyle factors: smoking, obesity, diet, exercise, drinking

Epidemiology

Non-modifiable risk

Gender, age, genetics, race

Primary Prevention

• No disease is present 
• Action can be taken to prevent disease ocurrence
• eg immunizations, condoms, anti-smoking commericals

Secondary Prevention

Disease is present but early stages

treatments are more effect in early stages

e.g. early stage breast cancer

Population-based Prevention

prevention measure is widely applied to the general population

e.g. water floridation

Example of skin-skin

transmission?

Direct or indirect?

Herpes Type 1

DIRECT

Example of food-borne

transmission?

Direct or indirect?

salmonella

INDIRECT

Example of mucous-mucous

transmission?

Direct or indirect?

STI

DIRECT

Example of water-borne

transmission?

Direct or indirect?

Hepatitis A

INDIRECT

Example of across placenta

transmission?

Direct or indirect?

toxoplasmosis

DIRECT

Example of vector-borne

transmission?

Direct or indirect?

MALARIA

INDIRECT

Example of through breast milk

transmission?

Direct or indirect?

HIV

DIRECT

Example of AIR-BORNE

transmission?

Direct or indirect?

CHICKENPOX

INDIRECT

Example of SNEEZE-COUGH

transmission?

Direct or indirect?

INFLUENZA

DIRECT

Example of TING-BORNE

transmission?

Direct or indirect?

SCARLATINA

INDIRECT

2 MODES of Contact Transmission

DIRECT

INDIRECT

3 MODES of Vehicle Transmission

AIRBORNE

WATERBORNE

FOODBORNE

2 Modes of Vector Transmission

Mechanical (on insect bodies)

Biological (lice, mites, mosquitos)

Epidemiologic triad

• A concept that helps explain that disease does not occur randomly.  Rather, disease occurrence is the result of the interaction between characteristics of the agent, host and environment (and, in some cases, vector).

Iceberg concept

A concept that helps explain that only a proportion of those persons who are exposed will become infected, and an even smaller proportion go on to develop symptoms and seek medical care.  As a result, often the cases of disease we are able to count are only “the tip of the iceberg.”

Endemic

Habitual presence of disease in a defined area.

Epidemic

An outbreak or any increase in disease that is above what is expected

Pandemic

• An epidemic that spans multiple countries.

Herd immunity

A concept that explains how a large group of people can be resistant to disease due to the fact that a high proportion of the population is immune (either due to vaccination or previous exposure).  The few in the group who are not immune only have a small chance of coming into contact with someone that is infected and thus are protected by herd immunity

Incubation period

The period of time between exposure and the development of symptoms.  For chronic diseases, this period is often very long and is sometimes referred to as the latent period

Epidemic curve

·         A graph that plots the number of cases (y-axis) over time (x-axis).  A true epidemic curve is drawn as a histogram, a special kind of bar chart in which there are no spaces between the vertical bars on the chart.  This is a tool that may be used during an outbreak investigation to help determine when most people became ill.

INDEX VS. PRIMARY CASE

(TRANSMISSION)

INDEX- 1ST CASE IDENTIFIED

PRIMARY- THE CASE THAT BRINGS THE INFECTION TO POPULATION

can be used interchangibly if unable to identify

EPIDEMIOLOGIC TRIAD

diseases is a result of forces w/i dynamic system consisting of:

AGENT, HOST, ENVIRONMENT

Reservoirs

A host that carries a pathogen w/o injury to itself and serves as a source of infection for other host organisms

(ASYMPTOMATIC INFECTIVE CARRIER)

VECTORS

a host that carries a pathogen w/o injury to itself and speads the pathogen to susceptible organisms

ASYMPTOMATIC CARRIERS OF PATHOGENS

EG. teste fly 

Sporadic level

occasional cases occurring at irregular intervals 

Hyperendemic level

persistently high level of occurrence

Surveillance

Passive Surveillance

Available data on reportable diseases or for which disease reporting is mandatory

• lacking quality-burden falls on busy health care provider
• inexpensive, easy to adopt

Active Surveillance

Hired staff carry out surveillance

Used to identify new cases

• Reporting more accurate
• expensive, time consuming

Sentinel Surveillance

Intensive active surveillance of cases of disease in portion of pop. 

• identifies trends
• may be hospital based

eg. surveillance systems: CDC reportable diseases

(i.e. AIDS, PERTUSSIS, SYPHILIS, MEASLES, E COLI)

Epidemiologic Transition

As income/development increases:

• childhood survival improves
• fertility decreases
• greater proportion of the population ages
• causes of death shift from infectious diseases to chronic diseases

Limitations of Prevalence

• does not consider the duration of illness
• prevalence cannot be used to estimate risk