Part One Disease Detectives (Foundational)

Disease

An infection that results in signs (objective) and symptoms (subjective).

Opportunistic disease

A disease that causes sickness when given the opportunity of a damaged or weakened immune system.

Nosocomial disease

An infection that is acquired in a hospital.

Iatrogenic disease

An illness that is caused by medication or a physician.

Chronic infection

An infection where the agent is continuously present and detectable.

Latent infection

An infection where the agent is continuously present, but can remain dormant before reactivation.

Incubation period

Time in between when a person comes into contact with an agent of disease and when they first show symptoms or signs of disease.

Latent period

Time in between when a person comes into contact with a pathogen and when they become infected.

Asymptomatic

Displays no signs or symptoms, but is infected and can carry the disease.

Susceptibility

To what extent a member of a population is able to resist infection.

Susceptible individual

A member of a population at risk of becoming infected by a disease.

Pathogenicity

The property of causing disease following infection. (proportion of infected individuals who develop disease; e.g. rabies is almost guaranteed you will get the disease)

Virulence

The property of causing severe disease.

Infectivity

The property of establishing infection following exposure. (how easily organism infects the host; measured often by ID50; ability of pathogen to ENTER, SURVIVE, and MULTIPLY; norovirus has high infectivity, only need a few particles)

Index case

Also known as 'patient zero'; the first case of a disease in a specific setting.

Etiology

The cause of a disease.

Pathology

The science of the study and diagnosis of disease and injury.

Determinant

Any factor that brings about change in a health condition.

Herd immunity

A critical proportion of a population is immune to a disease such that the entire population is protected.

Fulminant

A sudden and severe onset.

Quarantine

When you may have been exposed.

Isolation

When you have been exposed.

Vector

An organism that transmits disease, such as mosquitoes.

Vehicle

Any substance or object that can transmit disease to a host, not via a vector.

Agent

A factor that must be present in order for the disease to occur, including chemicals, bacteria, microorganisms, etc.

Arbovirus

Any of a group of viruses transmitted by mosquitoes, ticks, or other arthropods, including encephalitis, dengue, and yellow fever.

Zoonosis

Disease from animals to humans.

Holoendemic

A disease that is constantly present in a population at a very high level of infection, characterized by high prevalence and early onset.

Hypoendemic

A disease constantly present in a population at a relatively low level of infection.

Active Carriers

Individuals who are actively infected with a pathogen and can transmit it to others, even if they don't show symptoms.

Convalescent Carriers

Individuals who are recovering from an illness but continue to harbor and transmit the pathogen. (think themselves cured)

Healthy (or Asymptomatic) Carriers

Individuals who are infected with a pathogen but never develop symptoms, yet can still transmit the disease.

Incubatory Carriers

Individuals who are in the early stages of infection and are capable of transmitting the disease before showing symptoms.

Intermittent Carriers

Individuals who harbor and transmit the pathogen intermittently, with periods of shedding the pathogen and periods where they do not.

Passive Carriers

Individuals who are not infected but can mechanically transmit pathogens from one place to another, often on their skin or clothing.

Passive

Diseases are reported by healthcare providers. This type of surveillance, though simple and inexpensive, is often limited by incomplete reporting and quality variation in reporting.

Active

Health agencies contact health provers seeking reports. This ensures more complete reporting of conditions. Active surveillance is often used with a specific epidemiological investigation or during an outbreak.

Syndromic

Signs of the disease (such as school absences or prescription drug sales) are monitored as a proxy for the disease itself. The symptom must be infrequent and severe enough to warrant investigation of each identified case, and must be unique. This form of surveillance is often used when timeliness is key, diagnosis is difficult or time-consuming, or when detecting and defining the scope of an outbreak.

Sentinel

Professionals selected to represent a specific geographic area or group report health events to health agencies. This is used when high-quality data can't be obtained through passive surveillance. It involves monitoring trends or key health indicators and a limited network of reporting sites. Advantages include being able to implement intervention earlier and not being as reliant on doctors to diagnose disease. One downside to sentinel surveillance is that it's not as effective for detecting rare diseases or diseases that occur the outside the catchment areas of the sentinel sites.

Endogenous Transmission

overgrowth of organisms that are normally present in the genital tract

Fecal/Oral Transmission

through contaminated water or food (Cholera, Norovirus, Shigella)

Chronic Carrier

transmit the disease for extended period of time (carry pathogen for extended period of time)

Transient Carrier

Someone who can transmit an infectious disease for a short amount of time

Genetic Carrier

has inherited a disease trait but shows no symptoms