Epidemiology & Host-parasite Relationships

Question 0

Attack rate

Answer 0

Number of persons who developed on this versus the number exposed to the agent during a disease outbreak

Question 1

Incidence

Answer 1

Number of new occurrences of disease , injury, or desk in the study population during the time period being examined.

Indicates the frequency, rate of disease, ease of transition, and incubation period. It also indicates the attack rained and the secondary attack rate which is an indication of the ease of spread (transmission) of an agent.

Question 2

Secondary attack rate

Answer 2

Number of individuals who contract the disease within the incubation period from the first person with it i.e primary or index case

Question 3

seasonality

Answer 3

If the incidence rate is consistently higher during a specified time of year, the risk of developing the disease goes up at that time.

Question 4

Prevalence

Answer 4

Incidence (new cases) + old cases;

Number of people who currently have the disease

Question 5

Endemic

Answer 5

Disease of humans present in a particular region at an essentially constant level (expected incidents).

Question 6

Epidemic

Answer 6

Is that an increase in the incidence of a particular disease above the expected incidence – 1 standard deviation above endemic

Question 7

Pandemic

Answer 7

Applied to epidemics of unusually large proportions.

For example worldwide epidemic

Question 8

Zoonosis

Answer 8

A disease of animals present in a particular region at an essentially constant level

Question 9

Epizootic

Answer 9

A sudden increase in the incidence of a particular disease in the animal population

Question 10

Carrier

Answer 10

A person or animal contains, spreads or harbors an infectious agent

(Inapparent carrier, immune carrier, transient carrier)

Question 11

Inapparent (sub clinical) infection

Answer 11

No detectable clinical symptoms of infection but sero-conversion occurs

Question 12

Dormant (latent) infection

Answer 12

Carrier state

Question 13

Opportunistic infection

Answer 13

Infection caused by normal flora or transient bacteria when normal host offenses are compromised.

Example yeast infection after antibiotics

Question 14

Primary infection

Answer 14

Clinically apparent invasion and multiplication of microbes and body tissues, causing local tissue injury

Question 15

Secondary infection

Answer 15

Microbial invasion subsequent to primary infection.

Ex: bacterial infection after viral URI

Question 16

Mixed infection

Answer 16

Two or more microbes infecting the same tissue.

Example abscesses

Question 17

Acute infection

Answer 17

Rapid onset – hours or days ;

brief duration – days or weeks

Question 18

Chronic infection

Answer 18

Prolonged duration – weeks months or years

Question 19

Localized infection

Answer 19

Confined to a small area or to an organ

Question 20

Generalized infection

Answer 20

Disseminated to many body regions

Question 21

Pyogenic infection

Answer 21

Pus-forming

S. Aureus

Question 22

Fulminant

Answer 22

Actions that occur suddenly and intensely and are rapidly progressive

Question 23

Pathogenicity

Answer 23

The ability to produce disease and a host organism.

Question 24

Virulence

Answer 24

Degree of pathogenicity

Determined by virulence factors

Question 25

Frank pathogen

Answer 25

An organism which can cause disease any normal post; when identified in clinical specimens is considered to be the probable agent of disease

Question 26

Opportunistic pathogen

Answer 26

Etiologic agent isolated from a patient whose host defense mechanisms have been compromised

Question 27

Herd immunity

Answer 27

The spread of a communicable disease within a group based on the proportions of susceptible and immune individuals in the group.
Epidemics or outbreaks of disease occurs when the proportion of susceptible individuals is high and disappear as a proportion of immune individuals increase.

Question 28

Diseases spread by the ________ ______ require a higher proportion of immune individuals to prevent an outbreak than disease spread by _______ ________

Answer 28

Airborne route

Direct contact

Question 29

Portals of entry

Answer 29

Likelihood of infection increases the closer the proximity the POE is to the target tissue

Ex influenza virus

Question 30

Dose

Answer 30

Virulence of an organism is usually expressed as the amount that will infect (ID50) or kill (LD50) 50% of susceptible animals.

The larger the dose received the greater the chance for disease.

If an organism is highly virulent then fewer organisms will be required to cause disease.

Question 31

Adherence is a prerequisite for_______

Answer 31

Pathogenicity

Question 32

Rapidly growing organism produces _______ disease which is characterized by ______ onset and _________ progression

Answer 32

Acute disease

Rapid

Rapid

Question 33

In general a slow-growing organism produces a ________ disease which is characterized by a indolent or insidious onset and progression

Answer 33

Chronic

Question 34

Endotoxin (LPS)

Answer 34

A. Pyrogenic
B. Heat stable- survives autoclave
C. Does not form toxoids 
D. Broad spectrum of activity ( affects many species)
E. Produced by GRAM NEGATIVE organisms

Question 35

Exotoxins

Answer 35

A. Polypeptides are proteins that are either secreted or sell associated
B. Can be chromosome, plasmid encoded or carried on temperate bacteriophages
C. Usually heat labile
D. Can form toxoids (highly immunogenic)
E. Generally do not induced fever
F. Produced by gram-positive and Graham negative bacteria