Acute Disease Epidemiology Flashcards
Induction period
Similar to incubation period but refers to non-infectious disease
Incubation period
This extends from the time of first internalization of the agent to the time of the first symptom.
Cluster
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
Outbreak, epidemic
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
Endemic
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
Hyperendemic
Describes a circumstance wherein the level of endemicity is high
Holoendemic
Refers to a circumstance in which the disease is universally present, usually first infecting persons at an early age
Pandemic
An epidemic that has become widely distributed, usually internationally, and achieved a level of endemicity
Agent
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)
Degree of infectiousness
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
Reservoir
Prevalent repository and source of the agent: symptomatic case, asymptomatic carrier, animal, plant, soil, water, biologic product
Biologic vector
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
Mechanical vector
Any contaminated object by means of which physical transmission occurs, such as food or fingers
Infectious dose
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
Susceptibility to infection
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
Length and intensity of contact
The longer and closer the contact, the more likely the transmission
Herd immunity
A characteristic of a population, this refers to the prevalence of non-susceptibility, and provides an inverse measure of the probability of spread
Pathogenesis
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
Pathogenicity (virulence)
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
Host pathogen natural history
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
Specificity of symptoms and signs
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
Legal responsibilities
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
Reporting process
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.
Surveillance
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.
Outbreak investigation
Done to identify the agent and the mode of spread and implement appropriate control measures, ensure their effectiveness, and predict future occurrence
Intervention
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
Regulation
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
Nosocomial
Within the hospital environment
Person to person
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)
Iatrogenic
As a result of medical care
Case-fatality ratio
The proportion of affected cases of a disease who do not survive
Contamination
Introduction of a hazard, whether biological or chemical
Common source
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
Point source
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
Vector-borne
By virtue of transmission by a biologic disease vector
Zoonosis
Directly or indirectly acquired through animal contact
Autochthonous
Locally generated
Eradication
Complete elimination of a hazard, in contrast with control
Bioterrorism
Terrorism by means of biologic hazards, exclusive of chemical means
Secondary attack rate
The term used to denote the cumulative incidence rate among those exposed to a case of disease spread by person to person transmission
