Acute Disease Epidemiology Flashcards
(40 cards)
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.
