Acute Disease Epidemiology

Question 0

Induction period

Answer 0

Similar to incubation period but refers to non-infectious disease

Question 1

Incubation period

Answer 1

This extends from the time of first internalization of the agent to the time of the first symptom.

Question 2

Cluster

Answer 2

Refers to set of cases that appear to have been diagnosed unusually close to each other in time and space. After investigation, a cluster may be judged to have appeared by chance, or may turn out to be represent an outbreak

Question 3

Outbreak, epidemic

Answer 3

Both terms are formally defined as the occurrence of significantly more cases of a given condition than past experience would predict for that place, time and population, with the implication that an unusual level of exposure was responsible. While both terms are used to refer to a discrete local problem, the term epidemic may also refer to long term trend in occurrence

Question 4

Endemic

Answer 4

Term used to describe increasing levels of usual incidence in a population, in contrast with an unusual incidence, such as during an epidemic; endemic contrasts with epidemic, and refers to the usual existence of a condition

Question 5

Hyperendemic

Answer 5

Describes a circumstance wherein the level of endemicity is high

Question 6

Holoendemic

Answer 6

Refers to a circumstance in which the disease is universally present, usually first infecting persons at an early age

Question 7

Pandemic

Answer 7

An epidemic that has become widely distributed, usually internationally, and achieved a level of endemicity

Question 8

Agent

Answer 8

The infectious organism (RNA or DNA virus, prion, rickettsia, chlamydia, bacteria, mycobacterium, fungus, protozoan, helminth, arthropod), the toxin or genome produced by an organism (bacteria, algae, fungus, protozoan, coelenterate, arthropod, mollusk, fish, snake, lizard), the environmental hazard (dust, solvent, toxic chemical, metal, ionizing radiation, sunlight, heat, noise, repetitive trauma)

Question 9

Degree of infectiousness

Answer 9

Differs from pathogenicity or virulence. Infectious depends upon the nature of the source, the anatomical site from which transmission occurs, the number of viable infectious organisms transmitted, the viability of the agent between hosts, and the duration of the transmission. Thus: determined by characteristics of the transmitter, not the recipient, of the infection

Question 10

Reservoir

Answer 10

Prevalent repository and source of the agent: symptomatic case, asymptomatic carrier, animal, plant, soil, water, biologic product

Question 11

Biologic vector

Answer 11

Natural intermediate host for an agent (in which the agent grow or multiples). These include the mosquito (malaria, arbovirus), the tick (Lyme disease, Rocky Mountain spotted fever) or snail (schistosomiasis) which is responsible for spread to man

Question 12

Mechanical vector

Answer 12

Any contaminated object by means of which physical transmission occurs, such as food or fingers

Question 13

Infectious dose

Answer 13

That number of organisms required to produce a sustaining infection. Commonly measured in the laboratory by measures analogous to the LD50: I.e. That dose necessary to produce a lethal infection in 50% of those animals infected

Question 14

Susceptibility to infection

Answer 14

Used to describe the immunity of the exposed, whether inherited or acquires as a result of past exposure to disease or to vaccination. Not therefore a function of infectiousness. Susceptibility is a function of conditions at the time of transmission, to be distinguished from host conditions which bear on the subsequent effect of infection, and which influence pathogenicity

Question 15

Length and intensity of contact

Answer 15

The longer and closer the contact, the more likely the transmission

Question 16

Herd immunity

Answer 16

A characteristic of a population, this refers to the prevalence of non-susceptibility, and provides an inverse measure of the probability of spread

Question 17

Pathogenesis

Answer 17

Systemic or local toxin production, general or tissue-specific destruction, inactivation of defense mechanisms, competition for nutrients, physical obstruction of vital organs, induction of pathologic immune response

Question 18

Pathogenicity (virulence)

Answer 18

Infections vary greatly in the infection to disease ration, from a symbiotic relationship in which no symptoms are present, to invariable symptomatic disease. Once infection has occurred the damage done by the infection depends upon characteristics of the agent as well as upon those of the host. The ratio may be influenced in part by the transmitted doses, by factors which compromise the host defenses, and when considering the infections of animals, by the species of the host. Virulence is closely related to pathogenicity usually used when distinguishing between strains of the same agent

Question 19

Host pathogen natural history

Answer 19

The form that the infection takes depends upon the route by which the organism enters the body, the preference for and susceptibility of individual tissues, the period required for the replication of the organism, the means by which the agent spreads in the body, and the various immunologic and non-immunologic defenses of the host

Question 20

Specificity of symptoms and signs

Answer 20

The more easily the syndrome is recognized by experts, and especially by laypersons, the morse quickly the outbreak will be brought under control. This depends upon the uniqueness of the symptoms and the frequency of similar symptoms

Question 21

Legal responsibilities

Answer 21

State government has responsibility for acute disease control. The legislature mandates or instructs the state administration to nominate diseases to the reported. The responsibility for collecting reports, investigating hazards, including outbreaks, and instituting control measures if passed in to local governments. The federal government provides services through CDC including laboratory and epidemiology assistance, provided upon request from states. The CDC compiles reports of disease by state, monitors the trends, and passes the information back to states

Question 22

Reporting process

Answer 22

Physicians from the early warning network in the national disease surveillance effort. They along with the other health workers are legally responsible for reporting each case of a reportable condition by notifying the local health authority, either by telephone. If circumstance warrant, or, as usual, by mail using a confidential morbidity report form. The local health department forwards the report to the state health department, who in turn, if there has been an agreement to report the condition nationally, sends it on to the CDC. The latter is only authorized to investigate problems in federal facilities, such as veterans hospitals, Indian reservations, military hospitals, and federally administered territories.

Question 23

Surveillance

Answer 23

This term describes the public monitoring of health indices, not only reportable diseases but events and characteristic (incidence and prevalence) that serve as surrogates for the disease themselves. Surveillance differs from simple reporting or case ascertainment, because the works implies that a response is anticipated, especially if the events in question are disturbing, novel or otherwise important.

Question 24

Outbreak investigation

Answer 24

Done to identify the agent and the mode of spread and implement appropriate control measures, ensure their effectiveness, and predict future occurrence

Question 25

Intervention

Answer 25

The means depend entirely on the circumstance of disease and occurrence. They may include the interruption of a common source of exposure, control of insect vectors by eradication or placement of barriers, elimination of a biologic reservoir (removing animals, altering ecosystems, or even treating human cases), quarantine or isolation, passive or active immunization, or prophylactic treatment

Question 26

Regulation

Answer 26

Setting standards and monitoring restaurants and the food industry, water quality, maintaining control of tuberculosis, HIV, and other sexually transmitted disease, establishing vector control, and control of other environmental hazards

Question 27

Nosocomial

Answer 27

Within the hospital environment

Question 28

Person to person

Answer 28

Transmission by direct contact: airborne fomite, fecal-oral spread, venereal contact, congenital transfer (mother to infant during parturition), mechanical transfer (needle, blood transfusion, wound contamination)

Question 29

Iatrogenic

Answer 29

As a result of medical care

Question 30

Case-fatality ratio

Answer 30

The proportion of affected cases of a disease who do not survive

Question 31

Contamination

Answer 31

Introduction of a hazard, whether biological or chemical

Question 32

Common source

Answer 32

Origin of agent responsible for infecting or intoxicating multiple persons. If a food, can be a component of the original plant or animal, the result of contamination of the original plant or animal, contamination during transport, or contamination during food preparation or serving

Question 33

Point source

Answer 33

Refers to the appearance of a cluster of unusual cases appearing to vary in onset only by chance: I.e. Without biologically meaningful intervening periods. Such a finding suggests that the cases may have been exposed at the same point in time, with the interference that one exposure was common to all

Question 34

Vector-borne

Answer 34

By virtue of transmission by a biologic disease vector

Question 35

Zoonosis

Answer 35

Directly or indirectly acquired through animal contact

Question 36

Autochthonous

Answer 36

Locally generated

Question 37

Eradication

Answer 37

Complete elimination of a hazard, in contrast with control

Question 38

Bioterrorism

Answer 38

Terrorism by means of biologic hazards, exclusive of chemical means

Question 39

Secondary attack rate

Answer 39

The term used to denote the cumulative incidence rate among those exposed to a case of disease spread by person to person transmission