Pathology

is the scientific study of disease

etiology

the study of the cause of a disease.

pathogenesis

the manner in which a disease develops

infection

- the growth of microorganisms in the body

- the invasion or colonization of the body by pathogenic microorganisms

- the presence of a particular type of microorganisms in a part of the body where it is not normally found

disease

- an abnormal state in which part of all of the body is not properly adjusted or is incapable of performing normal functions

- occurs when an infection results in any change of a state of health.

normal microbiota

- the microoorganisms that colonize a host without causing disease

- aka normal flora

transient microbiota

- the microorganisms that are present in am animal for a short time without causing diease

- may be present for several days, weeks, or months, and then disappear

microbial antagonism

- growth of some microbes prevents the growth of other microbes

- normal microbiota protect the host against colonization by potentially pathogenic microbes by competing for nutrients, producing substances harmful to the invading microbes.

- aka competitive exclusion

symbiosis

- the living together of two different organisms or populations

-a relationship between two organisms in which at least one organism is dependent on the other

commensalism

a symbiotic relationship in which two organisms live in association and one is benefited while the other is neither benefited nor harmed.

mutualism

a symbiotic relationship in which both organisms or populations are benefited

probiotics

- live microbial cultures applied to or ingested that are intended to exert a beneficial effect

- probiotics may be administered with prebiotics, which are chemicals that selectively promote the growth of beneficial bacteria.

parasitism

- a symbiotic relationship in which one organisms exploits another without providing any benefits in return

- one organisms benefits by deriving nutrients at the expense of the other

- many disease-causing bacteria are parasites

opportunistic pathogens

a microorganism that does not ordinarily cause a disease but can become pathogenic under certain circumstances.

Koch's postulates

- criteria used to determine the causative agent of infectious disease

1) the same pathogen must be present in every case of the disease

2) the pathogen must be isolated from the diseased host and grown in pure culture

3) the pathogen from the pure culture must cause the disease when it is inoculated in a healthy, susceptible laboratory animal

4) The pathogen must be isolated from the inoculated animal and must be shown to be the original organism

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symptoms

- changes in body functions

- a change in body function that is felt by a patients as a result of a disease

sign

a change due to a disease that a person can observe and measure

syndrome

a specific group of sings or symptoms that accompany a disease

communicable disease

any disease that can be spread from one host to another, either directly or indirecly

contagious disease

a disease that is easily spread from one person to another

noncommunicable disease

a disease that is not transmitted from one person to another.

incidence

the fraction of the population that contracts a disease during a particular period of time

prevalence

- number of people in a populate who develop a disease at a specific time, regardless of when it first appeared

- takes into account both old and new cases

sporadic disease

a disease that occurs occasionally in a population

endemic disease

a disease constantly present in a population

epidemic disease

a disease acquired by many hosts in a given area in a short time

pandemic disease

epidemic disease that occurs worldwide

acute disease

develops rapidly but lasts only a short time

chronic disease

develops more slowly, and the body's reactions may be less sever, but the disease is likely to continue or reoccur for long periods.

subacute disease

a disease with symptoms that are intermediate between acute and chronic.

latent disease

a disease in which the causative agent remains inactive for a time but then becomes active to produce symptoms of the disease

herd immunity

the presence of immunity in most of a population

local infection

an infection in which pathogens are limned to a small area of the body

systemic (generalized) infections

- an infection throughout the body

- microorganism or their products are spread throughout the body by the blood or lymph

focal infection

- a systemic infection that began as an infection in one place

- Agents of a local infection enter a blood or lymphatic vessel and spread to other specific areas of the body

- can arise from infections in areas such as the teeth, tonsils, or sinuses.

Sepsis

- a toxic inflammatory condition arising from the spread of microbes

- the presence of a toxin or pathogenic organism in the blood and tissue

Septicemia

-systemic infection arising from the multiplication of pathogens in the blood

- the proliferation of pathogens in the blood, accompanied by fever; sometimes causes organ damage

- common example of sepsis

- aka blood poisoning

bacteremia

- presents of bacteria in the blood

Toxemia

presents of toxin in the blood

viremia

presence of viruses in the blood

primary infection

- an acute infection that causes the initial illness

secondary infection

- cause by an opportunistic pathogen after the primary infection has weakened the body's defenses.

subclinical (inapparent) infection

- an infection that does not cause any noticeable illness

predisposing factor

- makes the body more susceptible to a disease and/or may alter the course of the disease

incubation period

(1st development of disease)

- the interval between the initial infection and the first appearance of any signs of symptoms.

- no signs or symptoms

- the time of incubation depends on the specific microorganism involved, its virulence, the number of infecting microorganism, and the resistance of the host.

prodromal period

(2nd development of disease

- relatively short period that follows the period of incubation in some disease

- characterized by early, mild symptoms of disease

Period of illness

(3rd development of disease)

- the disease is most sever

- exhibits overt signs and symptoms of disease

- most sever signs and symptoms

period of decline

(4th development of disease)

- signs and symptoms subside

- vulnerable to secondary infections

period of convalescence

(5th development of disease)

- regains strength and the body returns to its prediseased state.

reservoir of infection

-a continual source of infection

carriers

organisms (usually refers to humans) that harbor pathogens and transmit them to others.

zoonoses

diseases that occur primarily in wile and domestic animals and ca be transmitted to humans.

contact transmission

spread of agent of disease by direct contact, indirect contract, or droplet transmission

Direct contact transmission

- is the direct transmission of an agent by physical contact between its source and a susceptible host

- no intermediate object is involved

- aka person-to-person

Indirect contact transmission

- occurs when the agent of disease is transmitted from its reservoir to a susceptible host by means of a nonliving object

fomite

a nonliving object that can spread disease

droplet transmission

- which microbes are spread in droplet nuclei (mucus droplets) that travel only a short distance

- disease agents that travel short distances are not regarded as airborne transmission

Vehicle transmission

- transmission of disease agents by a medium, such as water, food, or air.

- other media include blood and other body fluids,drugs, and intravenous fluids

waterborne transmission

pathogens are usually spread by water contaminated with untreated or poorly treated sewage

foodborne transmission

pathogens are generally transmitted in foods that are incompletely cooked, poorly refrigerated, or prepared under unsanitary conditions.

airborne transmission

spread of agents of infection by droplet nuclei in dust that travel more than 1 meter from the reservoir to the host.

vectors

animals that carry pathogens from one host to another

mechanical transmission

passive transport of the pathogens on the insect's feet, or other body parts.

Biological transmission

- the transmission of a pathogen from one host to another when the pathogen reproduces in the vector.

- arthropod bites an infected person or animal and ingests some of the infected blood.

nosocomial infection

- an infection that develops during the course of a hospital stay and was not present at the time the patient was admitted.

Nosocomial infection result from the interaction of several factors:

1) microorganisms in the hospital environment

2) the compromised (or weakened) status of the host

3) the chain of transmission in the hospital

compromised host

- a host whose resistance to infection is impaired.

- two principal conditions can compromise the host: broken skin or mucous membranes, and a suppressed immune system.

emerging infectious diseases (EIDs)

a new or changing disease that is increasing or has the potential to increase in incidence in the near future.

epidemiology

the science that studies when and where diseases occur and how they are transmitted

descriptive epidemiology

- entails collecting all data that describe the occurrence of the disease under study.

- relevant information usually includes information about the affected individuals and the place and period in which the disease occurred.

Analytical epidemiology

- analyzes a particular disease to determine its probable cause

- case control method: the epidemiologist looks for factors that might have preceded the disease.

- cohort method: epidemiologist studies two population: one that has had contact with the agent causing a disease and another that has now.

Experimental epidemiology

-begins with a hypothesis about a particular disease; experiments to test the hypothesis are then conducted with a group of people

Centers for Disease Control and Prevention (CDC)

- a branch of the U.S. Public Health Service located in Atlanta, Georgia, is a central source of epidemiological information in the United States.

Morbidity and Mortality Weekly Report (MMWR)

- CDC issues a publication

- is read by microbiologists, physicians, and other hospital and public health professional.

- contains data on morbidity and mortality

morbidity

the incidence of specific notifiable diseases

mortality

the number of deaths from these diseases

notifiable infectious diseases

are diseases for which physicians are required by law to report cases in the U.S. Public Health service.

Morbidity rate

the number of people affected by a disease in a given period of time in relation to the total population

Mortality rate

the number of deaths resulting from a disease in a population in a given period of time in relation to the total population