biol 343 priniciples of disease epidemiology and pathology

pathology

the study of disease

etiology

the cause of a disease

pathogensis

the manner in which a disease develops

infection

invasion/colonization of the body by pathogens

infectious disease

infections that cause changes in health states

kochs postulates

1. same pathogen in every case of the disease

2. pathogen must be isolated from the diseased host and cultured

3. the pathogen must cause the disease when inoculated in a healthy, susceptible laboratory animal

   1. the pathogen must be isolated from the inoculated animal and proven to be the original organism

when do koch’s postulates fail?

1. isolate cannot be cultured

2. isolate is not able to grow in laboratory animals

3. different diseases/conditions caused by the same organism

   1. similar symptoms caused by different microorganisms

symptoms

subjective changes in bodily function that are felt by a patient and usually not aparent to an observer

signs

objective changes in bodily function that can be measured or observed as a result of diseasesy

syndrome

a group of signs and symptoms that accompany a disease

communicable disease

disease that is spread from host to host

contagious disease

disease that is easily spread from one host to another

noncomunicable diseases

diseases that are not spread from one host to another

incidence

number of people who develop a disease during a particular time periodpe

prevalence

number of people who have a disease at a specified time, regardless of when it first appeared

sporadic disease

disease that occurs occasionallyend

endemic disease

disease constantly present in a population

epidemic disease

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

pandemic

worldwide epidemic

duration

average time that individuals have a disease from diagnosis to either being cured or dying

acute disease

symptoms develop rapidly, duration is short

chronic disease

symptoms develop slowly, last for a long periodsub

subacute disease

intermediate between acute and chronic

latent disease

causative agent is inactive for a time but then activates and produces symptoms

herd immunity

immunity in most of a population

severity

presence and extensiveness of a disease in the body and its ability to cause death

asymptomatic

no signs/symptoms

mild symptoms of COVID-19

fever, dry cough, tired, muscle pain, sore throat

moderate symptoms of COVID-19

breathlessness, tachycardia, persistent cough, higher fever

severe symptoms of COVID-19

pneumonia, extreme breathlessness, chest pain, high temperature, bluish lips/face

critical symptoms of COVID-19

SARS, inflamed alveolis

sepsis

toxic inflammatory condition arising from the spread of microbes/toxins from a focus of infection

infection fatality ratio

number of deaths by a disease:total number of infected individuals within a specific time period

case fatality ratio

proportion of individuals diagnosed with a disease who die from that disease within a certain period of time

local infection

pathogens are limited to a small area of the bodyse

systemic (generalized) infection

infection spread throughout the body by blood and lymph

focal infection

systemic infection that began as a local infection

bacteremia

bacteria in the bloods

septicemia

growth/proliferation of bacteria in the blood

toxemia

toxins in bloodv

viremia

viruses in the bloodpr

primary infection

acute infection that causes the initial illness

secondary infection

opportunistic infection after a primary infectionsu

subclinical infection

infection with no noticable signs or symptoms

predisposing factors for illness

nutrition, sex, genetic inheritance, climae, environment, vaccination status, age, lifestyle, behaviors, compromised host

disease development stages

incubation period, prodromal period, period of illness, period of decline, period of convalescence

incubation period

interval between initial infection and first signs/symptoms

prodromal period

short period after incubation, accompanied by early, mild, nonspecific symptoms

period of illness

disease is at its most severe point

period of decline

signs and symptoms subsidep

period of convalescence

body returns back to its prediseased state

reservoirs of infection

human reservoirs, animal reservoirs, nonliving reservoirs

zoonoses

diseases primarily present in wild/domestic animals that can be transmitted to humans

examples of non-living reservoirs

soil, water, food

direct contact transmission

transmission through close association between the infected and the susceptible host

congenital transmission

transmission from mother to fetus/newbord at birth

indirect contact transmission

spreads from host to host by fomites

fomites

non-living objects capable of carrying diseases

droplet transmission

transmission via airborne droplets within less than 1 meter

vehicle transmission

transmission by an inanimate reservoir

examples of vehicle transmission mechanisms

airborne, waterborne, foodborne

cross-contamination

transfer of pathogens from one food to another

vectors

arthropods

mechanism of vector transmission

mechanical or biologicalm

mechanical transmission

arthropod carries pathogen on its feet

biological transmission

pathogen reproduces in vector, is transmitted to host via bites or feces

nosocomial infections

infections acquired while receiving treatment in a health care facility

compromised host

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

leading cause of hospital associated infections

clostridium difficile (C. diff)

compromised host

individual whose resistance to infection is impaired, usually by disease, therapy, or burns

universal precautions to control healthcare associated infections

measures designed to reduce the transmission of microbes in health care settings that protect patients, residents, staff, and visitors from contact with pathogens

standard precautions to control healthcare associated infections

basic minimum practices for healthcare workers (i.e. hand hygiene, PPE, respiratory hygiene, cleaning and disinfection, patient placement)

transmission-based precautions

supplemental to standard precautions that are designed for suspected or known infections that are highly transmissible

how are pathogen numbers reduced

handwashing, disinfecting tubs used to bathe patients, cleaning instruments, disposable bandages

how is resistance to infection improved

prescribing antibiotics only when necessary, avoiding invasive procedures, minimizing use of immunosuppressants

why are E. coli O157:H7 and avian influenza emerging?

genetic recombination between organisms results in increased pathogen resilience

why is Vibrio cholerae O139 becoming an emerging infectious disease

evolution of exisiting organism has resulting in increased pathogen resilience

contributing factors for emerging infectious diseases

genetic recombination, evolution, widespread use of antibiotics, and inherent genetic instability of some microbes, changes to global climate, modern transportation, transport of vectors, ecological disaster, animal control measures

what kinds of microbes are considered genetically unstable?

RNA viruses

epidemiology

study of where and when diseases occur and how they are transmitted in populations

john snow

mapped the instance of cholera in london to a single water pump

ignaz semmelweis

showed that handwashing decreased instances of sepsis

florence nightingale

showed that improved sanitation decreased the incidence of epidemic typhus

reproductive number (Ro)

average number of people who will contract a disease from 1 infected individual

why is epidemiology important

it identifies factors and patterns concerning the spread of diseases, assembles data to outline disease incidence, predicts the probability of spread, and explores methods of disease control

descriptive epidemiology

collection and analysis of data (Snow)

analytical epidemiology

analyzes a particular disease to determine its probable cause or risk factors (Nightingale)

experimental epidemiology

involves a hypothesis and controlled experiments (Semmelweis)

clinical trial

test and control group

significance of case reporting

enables researchers to establish a chain of transmission and provide early warning of possible outbreaks of certain diseases

CDC

collects and analyzes epidemiological information in the US

Morbidity and mortality weekly report (MMWR)

reports of disease outbreaks, case histories, and summaries of the status of particular diseases

morbidity

incidence of a specific notifiable disease

mortality

deaths from notifiable disease

notifiable infectious diseases

diseases that physicians are required to report occurence

morbidity rate

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

mortality rate

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