X, Human Disease and Epidemiology Flashcards
Science dealing with the study of diseases.
Pathology
Entry of an infectious agent into the host.
Infection
Colonization
Invasion by an infectious agent resulting in the manifestation of signs and symptoms in the host.
Disease
Objective changes in the host as observed and measured by a physician (e.g. blood pressure, fever etc.)
Signs
Changes in bodily function felt by the patient (e.g. pain, malaise)
Symptoms
A specific group of signs and symptoms accompanying a particular disease. (e.g. AIDS)
Syndrome
The cause of an infectious disease process, the causative agent.
Etiology
Manner by which a disease develops. (mechanisms and
microbe-host dynamics)
Pathogenesis
A relationship in which microbes establish permanent residence in the host without producing disease.
Symbiosis
Normal microbiota prevent overgrowth of pathogens by competing for nutrients and producing inhibitory substances such as bacteriocins produced by E. coli against Salmonella and Shigella.
Microbial antagonism
A symbiotic relationship that benefits one organism while the other is not affected.
Commensalism
A relationship in which both organisms are benefited.
Mutualism
A relationship in which one organism is benefitted at the expense of another.
Parasitism
A harmless organism becomes pathogenic due to the
suppression of normal microbiota or when host’s immune response is impaired.
Opportunism
Two microbes acting together have greater effect than either acting alone (e.g. Mycoplasma infected cells are susceptible to death from viral
infections).
Syngergism
Koch’s postulates must be fulfilled in order to demonstrate that a specific microbe is the cause of a specific disease
The same pathogen must always be present in every case of the disease.
The pathogen must be isolated from the diseased host in pure culture on artificial media.
The pathogen recovered in pure culture must cause the disease when inoculated into a healthy susceptible laboratory animal.
The pathogen must be isolated from the infected animal again and must be shown to be the same pathogen as the original organism.
Spread of disease directly or indirectly from one host to another (e.g. tuberculosis)
Communicable diseases
Disease caused by microbes that cannot be spread from one host to another (e.g. tetanus via rusty nail)
Non-communicable diseases
Diseases that are easily spread from one person to another (e.g. flu)
Contagious disease
Fraction of the population (number of new cases/total
population) experiencing the disease during a certain period of time (e.g. 5-years of AIDS in the U.S., 2001-2005)
Incidence of a disease
Fraction of the population that has the disease at a given time (e.g. influenza during in winter)
Prevalence of a disease
Occasional occurrence of a disease (e.g. Legionnaire’s disease occurring at the American Legion Convention)
Sporadic
Constantly present in the population (e.g. Malaria is in Africa)
Endemic
Occurrence of disease beyond the normal experience of the population within a short period of time (e.g. cholera in Bangladesh after the tsunami)
Epidemic
Develops rapidly and lasts for a short time (e.g. Influenza)
Acute disease
Develops slowly but continuous and recurrent for long periods of time (e.g. leprosy)
Chronic disease
A category falling in between acute and chronic disease
e.g. bacterial endocarditis –SBE
Subacute infection
Pathogen is inactive for some time but becomes active later to produce symptoms (e.g. genital herpes)
Latent infection
A phenomenon when many people in the community are
immune to a certain disease (e.g. milkmaids vs. smallpox)
Herd immunity
Diseases that are new or changing, showing an
increase incidence in recent past or a potential for increase in the future (e.g. E. coli O157:H7)
Emerging infectious diseases
Invading microbes are limited to a small area of the body (e.g. boils and pimples)
Local infection
A local infection/microbes that spreads to other parts of the body via the blood and lymphatic system (e.g. Streptococcus sanguis introduced during a dental procedure)
Focal infection
Systemic or generalized infection
Presence of bacteria in the blood
Rapid multiplication of bacteria in the blood
Presence of toxins in the blood
Bacteremia
Septicemia
Toxemia
Acute infection causing the initial illness (e.g. Flu)
Primary infection
Caused by an opportunist after the primary infection
weakened the host’s defenses (e.g. pneumonia after the flu)
Secondary infection
Gender, genetic background, climate, age and nutrition = any factor that can greatly affect the occurrence of diseases in individuals.
Predisposing factors
Time between onset of infection and the appearance of
signs and symptoms.
Incubation period
Follows incubation period (in some diseases) as mild
symptoms of the disease.
Prodromal period
Overt signs and symptoms appear.
Period of illness
Signs and symptoms subside
Period of decline
Patient regains his pre-diseased state.
Period of convalescence
Continual source of the pathogen (e.g. animal or fomites)
Reservoir of infection
People harboring pathogens and transmitting these to others.
If they are diseased they are obvious transmitters. If asymptomatic, carriers.
Human reservoirs
Wild and domestic animals that serve as sources of pathogens causing zoonotic infections.
Through direct contact, contaminated food and water, consumption of infected animal products, insect
borne, or contact with contaminated fur or hide.
Animal reservoirs
Soil (e.g. tetanus), water contaminated with human
and animal feces (e.g. Salmonellosis)
Nonliving reservoirs
Transmission involving kissing, handshaking, bites or sexual intercourse.
Direct contact
Transmission in which agents of disease are spread over short distances, less than a meter. e.g. droplets of saliva or mucus from coughing sneezing.
Droplet infection
Transmission that involves an inanimate object such as drinking cup or soiled linen, also called fomites.
Indirect contact
Inanimate reservoirs such as food, water or blood that
serve as means of transmission of disease.
Vehicle transmission
Microbes in droplet nuclei or on dust carried over
distances beyond 1 meter (e.g. spores of fungi)
Airborne transmission
Arthropods that carry pathogens from host to another.
Vectors
Insects like flies that carry pathogens on their hairy bodies to food that is later swallowed by the host.
Mechanical vectors
Pathogens develop inside the insect and transmitted by bite or feces introduced into the bite wound.
Biological vectors
Routes by which a pathogen leaves the body (e.g. feces)
Portals of exit
.Most often caused by opportunistic pathogens on compromised patients due to broken skin or mucous membrane, suppressed immune system, impaired cell defense.
Previously caused by gram+ bacteria, gram- such as
Pseudomonas aeruginosa and E. coli now predominate. The emergence of MRSA and VRE has complicated the problem.
Nosocomial infections
Science which deals with the study of the frequency and spread of occurrence of diseases.
Epidemiology
Involves the collection of data such as geographical distribution, demographics, and the causative agent (where and when the disease occurred in the population)
Descriptive epidemiology
Epidemiologists look for common factors among the affected individuals in the population that might have preceded the disease outbreak.
Analytical epidemiology
Tests a hypothesis by experimentation (e.g. clinical trials for Ciprofloxacin using a double-blind study)
Experimental epidemiology
Central source for epidemiological information in the U.S. Publishes the Morbidity and Mortality Weekly Report (MWWR), which contains data about the morbidity (relative incidence of the disease) and mortality (deaths from a disease)
Centers for Disease Control (CDC) in Atlanta, Georgia
Those that physicians must report to the U.S. Public Health Service=USPHS. (e.g. anthrax, typhoid fever). The CDC is a branch of this agency.
Notifiable diseases
Coordinates public health efforts worldwide
World Health Organization. WHO
