2025 Science Olympiad: Disease Detectives Study Guide

Clinical Approach

primary role is diagnosis and treatment of illness in individuals, preventive medicine (e.g., immunizations, smoking cessation, obesity counselling and other behavioral/lifestyle concerns) has only been addressed recently - focus remains on the individuals.

Public Health Approach

primary role is in control and prevention of disease in populations or groups of individuals, some activities (e.g., diagnosing cases associated with outbreaks and treating persons with communicable diseases such as tuberculosis or syphilis) may overlap with those in clinical medicine.

John Snow

father of epidemiology

Clinical care

prevention, treatment, and management of illness and the preservation of mental and physical well-being through the services offered by medical and allied health professions; also known as health care

Determinant

factor that contributes to the generation of a trait

Health outcome

result of a medical condition that directly affects the length or quality of a person's life

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.

Descriptive epidemiology

involves identifying to the time, place, and the person involved in the onset of the health related event.

Analytical epidemiology

mainly concerned with finding the causes of the health-related event and to identify the interventions of the health problem.

Experimental study

investigators can control certain factors within the study from the beginning

Descriptive study

the epidemiologist collects information that characterizes and summarizes the health event or problem.

Analytic study

the epidemiologist relies on comparisons between different groups to determine the role of different causative conditions or risk factors.

endemic

disease or condition present among a population at all times

Outbreak

More cases of a particular disease than expected in a given area or among a specialized group of people over a particular period of time.

Epidemic

Large numbers of people over a wide geographical area are affected

Pandemic

an epidemic occurring worldwide, or over a very wide area, crossing international boundaries, and usually affecting a large number of people

Cluster

An aggregation of cases over a particular period closely grouped in time and space, regardless of whether the number is more than the expected number

Sporadic

A disease that occurs infrequently and irregularly.

risk

The probability that an individual will be affected by, or die from, an illness or injury within a stated time or age span.

rate

number of cases occurring during a specific period; always dependent on the size of the population during that period

ratio

the value obtained by dividing one quantity by another: a ratio often compares 2 rates

proportion

the comparison of a part to the whole as the number of cases divided by the total population--does NOT have a time dimension, can be expressed by fraction, decimal, or percentage

Normal flora

Microbes have a positive symbiotic relationship with other organisms

Mutualism

both organisms benefit

Commensalism

A relationship between two organisms in which one organism benefits and the other is unaffected

Parasitism

the condition (one organism is helped and the other is harmed) which takes place when humans are invaded by infectious microbes. A parasite-host relationship is created. The parasite is often called the infectious agent.

Natural history of a disease

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

Incubation period

the period between exposure to an infection and the appearance of the first symptoms for infectious diseases

Latency period

The period between exposure and disease appearance for chronic diseases

Agent

A microbial organism with the ability to cause disease.

Reservoir

A place where agents can thrive and reproduce.

Portal of exit

a place of exit providing a way for an agent to leave the reservoir

Mode of transmission

method of transfer by which the organism moves or is carried from one place to another

Portal of entry

An opening allowing the microorganism to enter the host

Susceptible host

A person who cannot resist a microorganism invading the body, multiplying, and resulting in infection.

vector

An animate intermediary in the indirect transmission of an agent that carries the agent from a reservoir to a susceptible host.

Fomite

A physical object that serves to transmit an infectious agent from person to person.

Zoonosis

An infectious disease that is transmissible from animals to humans.

Infectious dose

the amount of pathogen required to cause an infection in the host. Varies according to agent and and consumer's age/health

Period of communicability

the period when you are infectious and can spread your germs (whether bacteria, viruses, or parasites) to an uninfected person

Contamination

when a potentially infectious agent exists in the host but has not yet in invaded the tissues of the host. The microbe may be destroyed by the body defenses or it may become part of the normal flora

Infection

when the infectious agent begins its invasion of the host tissue and its rapid multiplication. The infection may be localized or it may spread to alternative sites as deeper organs or tissues becoming systemic

Disease

when the cumulative effects of the infection causes damage in the tissues

Infectivity

proportion of exposed persons who become infected

Pathogenicity

proportion of infected individuals who develop clinically apparent disease

Virulence

The proportion of persons with clinical disease, who after becoming infected, become severely ill or die.

Incidence Rate

the rate of occurrence of an event; number of new cases of disease occurring over a specified period of time; may be expressed per a known population size

Prevalence

number of cases of disease occurring within a population at any one given point in time

Goal of surveillance

Provide information that can be used for health action by public health personnel, government leaders, and the public to guide public health policy and programs

Step 1: Data Collection

Reported diseases or syndromes

Electronic health records (e.g., hospital discharge data)

Vital records (e.g., birth and death certificates)

Registries (e.g., cancer, immunization)

Surveys (e.g., National Health and Nutrition Examination Survey [NHANES])

Step 2: Data Analysis

__ by place is the usual method used to examine reports either by where the case was reported or, ideally, by where the illnesses occurred

__ by location allows prevention resources to be directed to where the exposure occurred.

Step 3: Data Interpretation

closely coupled with data analysis

By identifying the person, place, and time, one can more easily determine how and why the health event happened

Step 4: Data Dissemination

describes how to distribute information to those who need to know.

Methods of distribution include:

health agency newsletters, bulletins, or alerts

surveillance summaries and reports

medical and epidemiologic journal articles

press releases and social med

Step 5: Link to Action

without action, the collected data serves no purpose

Passive Surveillance

more common form of surveillance used by most local and state health departments; health care providers (like physicians) report notifiable conditions

Active surveillance

public health surveillance in which the health agency solicits reports. The health agency takes action, not the healthcare providers

Sentinel

Reporting of health events by health professionals who are selected to represent a geographic area or a specific reporting group

Is used when high-quality data are needed about a particular disease that cannot be obtained through a passive system

May be a disease, event, or population

Syndromic surveillance

Focuses on one or more symptoms rather than a physician-diagnosed or laboratory-confirmed disease

Is the analysis of medical data to detect or anticipate disease outbreaks

Has been historically used to target the investigation of potential cases

Its use for detecting outbreaks associated with bioterrorism is increasingly being explored by public health officials