BIO3 - Chapter 14

Principles of Disease & Epidemiology

pathology

the study of disease

etiology

the study of the cause of a disease

pathogenesis

the development of disease

infection

colonization of the body by pathogens

disease

an abnormal state in which the body is not functioning normally

about the human microbiome

established in the utero, can be acquired from food, people, and pets, remaint throughout life

normal microbiota

permanently colonize the host & don’t cause disease under normal conditions

transiet microbiota

may be present for days, weeks, or months

factors that determine distribution & composition of normal microbiota

nutrients, physical & chemical factors, host defenses & mechanical factors

microbiome in vaginal birth

lactobacillus & bacteroides

microbiome in cesarean birth

resembles the human skin; S. aureus

microbial antagonism (aka competetive exclusion)

competition between microbes

how do normal microbiota protect the host

competing for nutrients, producing substances harmful to invading microbes, affecting pH & available O2

probiotics

live microbes applied to or ingested into the body, inteded to exert a beneficial effect

symbiosis

the relationship between normal microbiota & the host

types of symbiosis

commensalism, mutualism, parasitism

commensalism

one organism benefits, the other is unaffected

mutualism

both organisms beneft

parasitism

one organism benefits at the expense of the other

opportunistic pathogen

pathogen that doesn’t cause disease but takes advantage of a “weakened opportunity” to cause infection; E. coli

Koch’s postulates procedure

• sample from diseased animal

• mirobe grown in pure culture & identified

• microbe innoculated into healthy animal

• disease reproducted in animal

• microbe from animal is isolated & grown in pure culture

koch’s postulates purpose

to prove the cause of an infectious disease

exceptions to Koch’s posstulates

• some pathogens can cause several disease conditions

• some pathogens cause disease only in humans

• some microbes have never been cultured

symptoms

changes in the body function that are felt by a patients as a result of disease

signs

changes in a body that can be measured or observed as a result of disease

syndrome

a specific group of signs & symptoms that accompany a disease

communicable disease

a disease that is spread from one host to another

contagious diseases

diseases that are easily & rapidly spread from one host to another

noncommunicable disease

a disease that is not spread from one host to another

incidence

fraction of a pop. that contracts a disease during a specific time; indicates the spread of disease

prevalence

fraction of a pop. having a specific disease at a given time; include both old & new cases; indicate severity of the disease

sporadic disease

disease that occurs occasionally in a pop.

endemic disease

disease constantly present in a pop. - common cold

epidemis disease

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

pandemic disease

worldwide epidemic - covid

herd immunity

immunity in most of a pop.

acute disease

symptoms develop rapidly

chronic disease

disease develops slowly

subacute disease

symptoms between acute & chronic

latent disease

disease with a period of no symptoms when the causative agent is inactive

local infection

pathogens are limited to a small area of the body

systemic (generalized) infection

an infection throughout the body

focal infection

systemic infection that began as a local infection

sepsis

toxic inflammatory conditions arising from the spread of microbes, especially bacteria or their toxins, from a focus of infection

septicemia

growth of bacteria in the blood

bacteremia

bacteria in the blood

toxemia

toxins in the blood

viremia

viruses in the blood

primary infection

acute infection that causes the initial illness

secondary infection

opportunistic infection after a primary (predisposing) infection

subclinical disease

no noticeable signs or symptoms (inapparent infection)

predisposing factors

factors that make the body more susceptible to disease

predisposing factors examples

gender, inherited traits, climate & weather, fatigue, age, lifestyle, chemotherapy, emotional distrubances

incubation period

interval between initial infection & first signs & symptoms

preodromal period

short period after incubation;early, mild symptoms

period of illness

disease is most severe

period of decline

signs & symptoms subside

period of convalescence

body returns to its prediseased state

causes of the spread of infection

reservoirs of infection & transmission of disease

reservoirs of infection ex

human (AIDS, gonorrhea)

animal (rabies, lyme disease)

nonliving (botulism, tetanus)

significance of human carriers

may have inapparent infections or latent diseases

methods of transmission of disease

contact, vehicle, vectors

methods of contact

direct, congenital transmission, indirect, droplet

direct contact

req close association between infected & susceptible host

congenital transmission contact

transmission from mother to fetus or newborn at birth

indirect contact

spread by fomites

fomite

any nonliving object involved in the spread of an infection, such as clothes, utensils, & furniture

droplet contact

transmission via airborne droplets

vehicle transmission

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

vectors

arthropods (fleas, ticks, mosquitoes, most common); transmission via mechanical or biological transmission

what are the 2 general methods vectors transmit disease by

mechanical transmission & biological transmission

mechanical transmission

arthropod carries pathogen on feet

biological transmission

pathogen reproduces in vector

healthcare-associated infections (HAIs)

aka nosocomial infections; acquired while recieveing treatment in a health care facility

factors that make it easy for HAI to occur

microorganisms in the hospital env

compromised host

chain of transmission in a hospital

compromised host

an individual whose resistnce to infection is impaired by disease, therapy, or burns

methods of controlling HAIs

• universal precautions

• reducing number of pathogens

• infection control committees

what are the universal precautions

standard & transmission-based precautions

standard precautions

basic, minimum practices

transmission-based precautions

supplemental to standard precautions; designed for known or suspected infections

types of transmission-based precautions

contact, droplet, airborne precautions

ways to reduce # of pathogens

handwashing, disinfecting tubs used to bather patients, cleaning instruments scrupulously, using disposable bandages & intubation

emerging infectious diseases (EID)

diseases that are new, increasing in incidence, or showing potential to increase in the near future

contributing factors of EIDs

genetic recombination, evolution of new strains, inappropriate use of antibiotics & pesticides, changes in weather patterns, modern transportation, ecological disaster, war, & expanding human settlement, animal control measures, public health failure

epidemiolody

study of where & when diseases occur

role of epidemiologists

determine the etiology of a disease, ID other important factors concerning the spread of disease, develop methods for controlling a disease, assemble data & graphs to outline incidence of disease

descriptive epidemiology

collection & analysis of data

analytical epidemiology

comparison of a disease group & a healthy group

experimental epidemiology

controlled experiments

what is case reporting

health care workers report specified disease to local, state, & national offices

significance of nationaly notifiable diseases

physicians are required to report occurrence

morbidity

incidence of a specific notifiable disease

mortality

deaths from notifiable diseases

morbidity rate

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

mortality rate

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

A

incubation period

B

prodromal period

C

period of illness

D

period of decline

E

period of convalescence