Ch18 Exam 4 Flashcards
disease
a disturbance in the normal functioning of an organism
infectious disease
any disease caused by a microbe
communicable diseases
What is the opposite called? (easy)
infectious diseases that can be transmitted between individuals
non-communicable diseases
contagious disease
a communicable disease that can be transmitted easily
What types of diseases are:
Tetanus
AIDS
measles
How are they all alike?
non-communicable
communicable
contagious
All are infectious diseases (caused by microbes)
zoonotic diseases
(give an example)
caused by microbes naturally in animals that cause disease when transmitted to humans
rabies
pathogen
pathogenesis
infection
a microbe that causes disease
the way in which a pathogen causes disease
the replication of a pathogen in/on a host
symptoms
signs
disease state apparent to the patient (difficult to quantify)
disease state noticed by an outside party
Primary pathogens
Opportunistic pathogens
produce disease readily anytime (like “Bacillus anthracis”/”Yersinia pestis”)
cause disease only under certain circumstances (like “Candida albicans” in a WEAKENED immune system)
People with HIV disease represents the largest group of people with ____________.
weakened immune systems
Is poliovirus an opportunistic or primary pathogen?
primary
case to infection (CI) ratio
the number of people infected that develop the disease
What is the CI ratio of :
Measles?
Poliovirus?
.95 (95% of people with the measles virus will develop the disease)
<.01 (less than 1% of people infected will develop the disease)
pathogenicity
virulence
What is the pathogenicity of species in the:
Shigella genus?
Salmonella genus?
The ability of a microbe to cause disease (measurement)
The intensity of the disease caused by the microbe
high pathogenicity (the ingestion of a few cells can cause disease)
low pathogenicity (ingestion of 1000s of cells causes disease)
Give an example of a strain with high virulence
1918 strain of influenza
What may account for differences in virulence?
Can the virulence of one pathogenic species to another be compared? Why/Why not?
genetic differences between strains of a pathogen
Not really, diseases that cause different symptoms, make it hard to figure out which is more serious or not (page 628)
attenuation
decrease in the virulence of a pathogen
What provides more accurate/objective measures of virulence?
The LD50 (amount of pathogen/toxin that kills about 50% of test subjects)
The ID50 (amount of pathogen/toxin that infects about 50% of test subjects)
What is the LD50 of the Tetanus Toxin?
Vibrio cholerae?
What does this indicate
about 0.001 μg kg−1
about 250 μg kg−1
(Tetanus toxin is 250,00 times more potent; lower values = higher potency)
carrier
one that becomes infected but shows no symptoms (and may transmit to others); asymptomatic
how to microbes cause disease (generally)
(1) entry in host
attachment/invasion of specific cells
evade host defenses
obtain nutrients from host
leave the host
(like a robber coming to steal and dipping)
virulence factors
products that boosts the ability of a pathogen to cause disease
what determines the host range of a pathogen?
what can alter this?
(give an example)
the ability to attach, invade, and replicate within a host
molecular changes in the pathogen
canine parvoviruses (CPV2a & CPV2b)
antigenic variation
a host immune system evasion mechanism; pathogen alters surface antigens so as to prevent host recognition;
thus the avoidance of elimination
latent infection
When does reactivation occur?
What type of virus does this
the genome/micobr is present within the cells but does not produce new virions (if so, very few)
when host experiences some cellular stress
herpes virus
autophagy
the induction of cell death by the host to limit virus spread, though intracellular degradatipn
apoptosis
induction of cell death by host, resulting in cell suicide through DNA fragmentation
necrosis
host-induced cell death that results in cell rupture/ release of toxic cell contents
causing more damage/ inflammation
(unlike apoptosis quietly dying)
this occurs when cells are injured by structural damage/ loss of oxygen (due to trauma/ infection)
What is the difference between apoptosis and necrosis?
Necrosis causes collateral damage to other healthy cells
What do viruses commonly do relative to apoptosis to ensure virions are produced?
prevent apoptosis early in infection cycle
induce apoptosis late in infection cycle
OR infection through apoptotic body formation
restriction-modification system
What can pathogens do to evade this system
methylation (adding methyl groups) of host DNA to avoid self-cleavage by restriction enzymes
`
unmethylated DNA OF Invading pathogens may be cleaved and degraded by host restriction enzymes
inhibit host cell inhibition enzymes
methylated DNA prior to cleavage
CRISPR-Cas
an adaptive immune system existing in most bacteria/ archaea, preventing infection
the system allows researchers to alter DNA
Cas9
Cas13
(protein most used by researchers) targets dsDNA
targets RNA
toxins
what component of gram+ bacteria can act as a toxin
gram-?
substances produced by an organism that damage the host
lipoteichoic acid
lipopolysaccharide
Do viruses produce toxins? If not, how so?
Generally not, they usually replicate within a cell
For a pathogen to survive, what must they do? Why?
They must successfully transmit to other hosts, or other environments (as hosts eventually die)
transmission
the spread of an infectious agent from its source to a new host
direct transmission
indirect transmission
the spread of an infectious agent via physical contact between infected and susceptible individuals
the spread via other objects like water, food, etc.
fomite
a contaminated inanimate object capable of spreading pathogens
fecal-oral transmission
airborne/aerosol transmission
transmission in which pathogens excreted in feces of one individual is ingested by another
pathogens that replicate in the respiratory tract transmitted
vector-borne transmission
mechanical transmission
biological transmission
an arthropod vector (like a mosquito/tick) carries a pathogen from one host to another
a type of transmission that involves a vector PHYSICALLY carrying pathogen (the vector does not get infected)
vector borne transmission where that vector gets infected
sexual transmission
STIs
transmission that occurs through vaginal/anal/oral sex
sexually transmitted infections - infectious diseases spread through sex (like HIV)
vertical transmission
horizontal transmssion
transmission that occurs from parent to child (what HIV can do)
transmission that occurs amongst members of a species
zoonotic transfers
reservoir host
dead-end-hosts
transmission from an animal reservoir host to a human
species that a pathogen usually infects
incidental hosts for zoonotic transfers (not efficiently transferred from person to person) (like H5N1 influenza)
epidemiology
the study of disease patterns in populations (like cancer, obesity, genetic diseases, etc.)
morbidity rate
mortality rate
rate of disease
rate or death associated with diseases
(these rates are investigated by epidemiologists)
a case
how are asymptomatic individuals identified as a case?
an individual that exhibits the disease/ infected but may/may not be showing signs/symptoms
through PCR, culture, or ELISA (diagnostic testing)
incidence
prevalence
Which is larger? WHY?
of new cases appearing in a population during a SPECIFIC time period
total # of cases in a population at a particular point in time/ during a particular time period
prevalence since it includes both new/ preexisting cases
What do measures of incidence and prevalence show?
tell the level of infectious disease in a population
allow comparisons between populations over time
emerging diseases
emerging pathogens
known/unknown diseases with a recent significant increase in incidence
pathogens associated with emerging diseases
endemic diseases/agents
one that is consistently present in a specific population (like rabies in North American foxes)
incidence can decrease/ increase depending on seasons, immunity, etc.
epidemic
outbreak
incidence of a disease that significantly rises above normally expected for a population
An unexpected cluster of cases within a short period of time in a localized population
(to terms may be used interchangeably)
pandemic
an epidemic affecting populations globally at the same time (concurrently)
made up of (interpandemic, alert, pandemic, and transition phase)
T or F: cases of infectious diseases occur randomly.
False; they occur in patterns
common source epidemic
an outbreak that occurs when the single source that infects the population is exposed
incubation period
the period in which the pathogen enters and the illness appears
T or F: Cases in common source epidemics tend to remain isolated NEAR the local source of infection
True
propagated epidemic (page 647)
an outbreak that results from infection passing from one host to another indirectly or directly (like from COVID-19)
What is the common trend of propagated outbreaks
and increase in incidence as people are getting infected, until reaching a peak,
where a good amount of people are infected, immune, or dead
What is the difference between a common source epidemic (CSE) and a propagated epidemic (PE)
PEs continue to appear in more than one incubation period (as infected people spread to others, the case #s ^)
What doesn’t epidemiology allow us to determine
Whether a specific microbe has a specific disease (only how infections spread through a population)
Koch’s postulates
demonstrates that a specific microbe causes a specific disease
According to Rob Koch, what criteria should be met to prove a microbe causes a disease?
- the microbe exists in every individual with the disease and account for signs/symptoms
- should not be associated with other diseases
- should cause same disease after being isolated
Warren/Marshal
got nobel prize for proving stomach ulcers are caused by H. pylori
What did Koch observe relative to pathogens and individuals?
Not all individuals react to pathogens in the same way
molecular Koch’s postulates
by Stanley Farklow
virulence factor gene (VGF) should be present/ expressed
inactivation of VGF should = decreased virulance
reversion of VGF = virulence restoration
VGF should be expressed during an infection
resistance to VF must have protection
pathogenicity islands (PAIs)
regions of chromosome that contain virulence factor genes
T or F: Evolutionary pressure, it appears, has selected for the linkage of these individual virulence factor genes into a cohesive genetic structure
True
How may an emerging/ new disease arise?
zoonotic transfer
microbe becomes more virulent
pathogen becomes resistant to antimicrobial drugs
spillover
when an existing pathogen encounters a new population
SIV (simian immunodeficiency virus)
HIV evolved from this, a virus found in various non-human primates throughout Africa
clades
genetically distinct subtype of a species
What causes Lyme disease?
the bacterium Borrelia burgdoferi
