Disease Detectives

Scioly Disease Detective events

Epidemiology

The study of the distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.

Frequency

The number of health events and its relationship to the size of the population

Pattern

The occurrence of health-related events by time, placement and person.

Determinants

Any factor, whether event, characteristic, or other definable identity that brings about a change in a health condition or other defined characteristic

Endemic

Regularly occurring in an area or community

Public health surveillance

Ongoing, systematic collection, analysis, interpretation, and dissemination of health data to help guide public health decision making and action. Essentially equivalent to monitoring the community

Field investigation

Results from surveillance. It may be limited, like a phone call, or could be coordinated efforts of many people to characterize the extent of an epidemic and its cause.

Analytic studies

Designing, conducting, analyzing, and interpreting a study to investigate an outbreak further

Effectiveness

The ability of a program to produce the intended or expected results in the field

Case definition

A set of standard criteria for classifying whether a person has a particular disease, syndrome, or other health condition.

Case classifications

Suspected, probable, confirmed

Rate

# of cases/size of population per unit of time

Descriptive epidemiology

Covers time, place and person

Secular (long-term) trends

Graphed over years or long periods of time

Epidemic period graph

y axis: # of cases

x axis: time period

Displayed as a histogram with boxesS

Spot map

A map used for clusters or outbreaks with limited case numbers. An x or dot is marked on the location most relevant to the disease of interest (ex: John snow’s cholera investigation)

Personal characteristics

Are analyzed because they can affect illness. The two most common are age and gender at birth, but ethnicity, race and socioeconomic status may also be considered

Analytic epidemiology

Uses observations made by descriptive Epidemiology to create and test hypotheses

Experimental studies

The investigator controls and manipulates variables, uses a controlled process of exposure, and then tracks the individuals or community over time to detect the effects of the exposure

Observational study

Observation of the exposure and disease status of each study participant (ex: John Snow cholera outbreak)

Cohort studies

Epidemiologist records whether or not a person was exposed or not, and then follows up to see if they developed the disease

Follow up or prospective cohort study

The participants are enrolled as the study begins and then followed over time to identify outcomes of interest

Retrospective cohort study

The exposure and outcomes have already occurred

Case-control study

A type of observational study where a group of people with the disease is compared to a group without the disease to compare previous exposures between the two groups. They can then estimate what exposure caused the disease based on the differences between the two groups.

Cross sectional study

A type of observational study that measures exposure and disease status at the same time. It is often used to assess the prevalence of a disease without considering the duration.

Epidemiologic triad

A traditional model for causation of infectious disease. It consists of an agent, a susceptible host, and an environment that brings the host and the agent together

Causal pies

Individual factors that contribute to the diseases make up the pie, called component causes, build up to make a full pie that might be a causal pathway, called a sufficient cause. A component that occurs in every pathway is known as a necessary cause

Natural history of a disease

The progression of a disease process in an individual over time in the absence of treatment

Incubation period (infectious diseases) or latency period (chronic disease)

The time between exposure to the disease and onset of disease symptoms. It is harder to detect diseases during this period, but treatments are often more effective if administered.

Subclinical disease

A condition where the diseased state has begun, but no symptoms have yet occurred

Clinical disease

A condition in disease where symptoms have begun

Spectrum of disease

The range in severity of an illness from being hidden (subclinical) to being severe or fatal.

Infectivity

The proportion of people exposed to an infectious agent that become infected

Pathogenicity

The proportion of infected individuals who develop clinically apparent disease

Virulence

The proportion of clinically apparent cases that are severe or fatal

Carriers

People who are infectious but have subclinical diseases

Chain of transmission

When an agent leaves its reservoir or host through a portal of exit, is conveyed through some mode of transmission, and enters through an appropriate portal of entry to infect a susceptible host

Resevoir

The habitat in which the agent normally lives, grows, and multiplies. May be human, animal, environmental

Portal of exit

The path by which the a pathogen leaves its host

Direct transmission

An infectious agent is spread from a reservoir to a susceptible host via direct contact or droplet spread

Indirect transmission

The transfer of an infectious agent from a reservoir to a host by suspended air particles, inanimate objects (vehicles), or animate intermediaries (vectors)

Vehicles

May indirectly transmit an infectious agent and include water, food, biologic products (blood), and other inanimate objects

Vectors

May carry an infectious agent through purely mechanical means or may support growth or changes in the agent, and include mosquitoes, fleas, ticks, and other organisms.

Portal of entry

The manner in which a pathogen enters a susceptible host

Interventions

Aimed at controlling or eliminating agent at the source of transmission, protecting portals of entry, or increasing host’s defenses

Endemic level

The amount of a disease that is usually present in a community

Sporadic

a disease that occurs infrequently or irregularly

Hyperendemic

When there is a high and persistent level of disease in an area

Epidemic

An often sudden increase in the number of cases beyond what is usually expected for a population in that certain area

Outbreak

Carries the same definition as epidemic, but usually used for a more limited area

Cluster

An aggregation of cases grouped in a place and time that are suspected to be greater than the number expected

Pandemic

An epidemic that has spread over several countries or continents, usually affecting a large number of people

Common source outbreak

An outbreak in which a group of people are all exposed to an infectious agent or toxin from the same sourve

Point-source outbreak

A type of common-source outbreak where the group is exposed over a brief period, so everyone becomes ill within one incubation period. The graph of this has a steep upslope and a gradual downslope

Continuous outbreak

A type of common-source outbreak where case-patients are exposed over a period of days, weeks, or longer

Intermittent outbreak

A common-source outbreak where the exposure to the disease is intermittent

Propogated aoutbreak

Results in transmission from one person to another. Cases here occur over multiple incubation periods

Mixed epidemics

Have features of both common-source epidemics and propagated epidemics. Occur often when a common-source outbreak is followed by a person-to-person spread.