BIOL 251 Exam 3 Epidemiology

T/F: Normal microbiata usually cause disease.

F, they do not usually cause disease.

T/F: Normal microbiata do not usually cause disease.

T

T/F: Normal microbiata never cause disease.

F. Normal microbiata usually do not cause disease.

What is symbiosis?

The relationship between 2 organisms where at least one organism benefits

What is commensalism?

One organism benefits, the other is unaffected

Staphylococcus epidermis on the skin is what type of relationship between microbe and host?

Commensalism -  One organism benefits, the other is unaffected

Escherichia coli in the intestine is what type of relationship between microbe and host?

Mutualism — Both organisms benefit

What is mutualism?

Both organisms benefit

What is parasitism?

One organism benefits; other is harmed

Pathogenic microorganisms is what type of relationship between microbe and host?

Parasitism — One organism benefits; other is harmed

What are opportunisitic pathogens?

A microorganism that usually/typically does not cause disease in healthy individuals but can cause serious infections in people with weakened immune systems. 

What kind of factors affect normal microbiota?

Host factors 

What is transient microbiota?

• Microorganisms that may be present for several days, weeks, or months, but then disappear.

• May or may not cause disease

Microorganisms that may be present for several days, weeks, or months, but then disappear are called

transiet microbiota

Microorganisms that establish a permanent residence are called

normal microbiota

Microorganisms that do not USUALLY cause disease are called

normal microbiota

Microorganisms that may or may not cause disease are called

Transient microbiota

What is microbial antagonism? What is another name for it?

Competitive exclusion — members of the microbiome protect the host from colonization by pathogens

Competition for nutrients and space in the gut microbiome is an example of

microbial antagonism, a benefit of normal microbiota

T/F: When members of the microbiome protect the host from colonization by pathogens, microbial antagonism, this is a benefit of transient microbiota 

F, this is a benefit of NORMAL microbiota 

E. coli producing bacteriocins in the intestine is an example of

The production of harmful substances, which is microbial antagonism, a benefit of normal microbiota

lactobacilli produce acid and hydrogen peroxide in the vagina, and some members of the microbiome use up oxygen in the intestine, is an example of

Effect conditions (pH, O2 availability) in the surrounding environment which is microbial antagonism, a benefit of normal microbiota

What is an infection? Microorganisms carry out how much of their life cycle in the host body?

• Invasion or colonization of the body with pathogenic microorganisms 

• Microorganisms carry out at least part of their life cycle in the host body

What is disease?

Any change in health caused by an infection

What is pathology?

Scientific study of disease

What is etiology?

causative agent of a disease

What is pathogenesis?

Manner in which a disease develops

What does Koch’s postulates show? What are its conditions?

Shows that a specific infectious disease is associated with a particular microorganism. 

classic steps used to prove that a specific microbe causes a specific disease:

Koch's postulates were devised as general guidelines to identify infectious microbes that could be detected with the available methods and that were demonstrably alive (i.e., capable of independent metabolism, growth, and reproduction).

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 same disease when inoculated into a healthy, susceptible host. 

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

What are the exceptions to Koch’s postulates?

• Culture requirements – may not be possible to grow an organism in pure culture on artificial media (Mycobacterium leprae)

• Multiple pathogens may cause the same signs and symptoms (meningitis)

• Some pathogens can cause multiple disease conditions (Streptococcus pyogenes)

• Lack of a non-human host (HIV)

When classifying infectious disease, what are symptoms?

Symptoms: Subjective changes in body function (things you feel)

When classifying infectious disease, what are signs?

Signs: Objective changes in body function that can be observed and measured

When classifying infectious disease, what is a syndrome?

Syndrome: a specific group of signs and/or symptoms that may always accompany a particular disease

Jason is a 28 year-old man. Yesterday, he started experiencing a headache, fever, nausea, and diarrhea. Which of these are signs of a disease and which are symptoms?

• Headache - Symptom

• Fever - Sign

• Nausea - Symptom

• Diarrhea - Sign

What is a communicable disease?

a disease in which an infected person transmits an infectious agent to another person (directly or indirectly)

What is a contagious disease?

highly communicable disease that can spread easily and quickly from one person to another. 

What is a noncommunicable disease?

not spread from host to host

Tetanus is an example of what kind of infectious disease?

Noncommunicable disease — not spread from host to host

What is contact transmission?

spread of a disease agent by contact

What is direct contact transmission?

transmission by physical contact with an infected person

• Touching 

• Kissing 

• Sexual intercourse 

What is indirect contact transmission?

transmission by a nonliving object (fomite)

What is droplet transmission?

transmission by droplet nuclei that travel less than 1 meter

What is a vector? What is mechanical and biological transmission?

Vector – animal that carry pathogens from one host to another

• Mechanical transmission – passive transport of pathogen on body

• Biological transmission – active process

  • Insect vector bites host and ingests infected blood

  • Pathogen replicates in the vector

  • Insect passes pathogen to new host (feces, biting)

What is vehicle transmission?

spread of a disease agent by a medium

What is waterborne transmission, and what type of disease transmission is it?

Waterborne transmission, transmission by contaminated water. It is a type of vehicle transmission. 

What is foodborne transmission, and what type of disease transmission is it?

transmission by consumption of contaminated food (improperly cooked, poorly refrigerated, prepared in unsanitary conditions). It is a type of vehicle transmission. 

What is airborne transmission, and what type of disease transmission is it?

transmission by droplet nuclei that travel more than 1 meter. It is a type of vehicle transmission. 

T/F: Masks can catch droplets and some aerosols.

T. Aerosols are slowed and travel shorter distance. Reduces risk of transmission.

T/F: Masks cannot catch droplets and aerosols.

F. Masks can catch droplets and some aerosols. Aerosols are slowed and travel shorter distance. Reduces risk of transmission.

Jason’s doctor indicates that he likely acquired this infection due to food he had consumed. What type of transmission is this?

Vehicle transmission

What is an acute disease?

a disease that develops rapidly, but lasts only a short time

What is a chronic disease?

a disease that develops slowly, but is often less severe; likely to continue or recur for long periods

What is a latent disease?

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

What is subclinical disease?

no noticeable illness

What is a local infection?

infection in which the invading microorganisms are confined to a relatively small area of the body

What is a systemic infection?

infection in which the invading microorganisms are spread throughout the body (blood or lymph)

What type of infection is Septicemia? (Septicemia– bacteremia, toxemia, viremia)

a life-threatening systemic infection

What is a primary infection?

acute infection that causes the initial illness

What is a secondary infection?

infection caused by an opportunistic pathogen after the body’s defenses have been weakened by a primary infection

Describe the incubation period in the development of disease.

• Period between initial infection and the appearance of signs or symptoms

• Number of microbes increases, but no signs or symptoms

Describe the prodromal period in the development of disease.

• Period of early, mild symptoms in some disease

• Relatively short 

Describe the period of illness in the development of disease.

• Disease is most severe

• Overt signs and symptoms

• Ends when the host immune system starts to overcome the pathogens

  • If immune response is unsuccessful, the patient dies

Describe the period of decline in the development of disease.

• Signs and symptoms subside, but are still present

• Vulnerable to secondary infections

Describe the period of convalescence in the development of disease.

• Body returns to pre-disease state

• No more signs or symptoms

• Microbes are eliminated

Jason’s doctor tells him that he has an infection caused by Salmonella enterica. She indicates that he should start to feel better in a few days, but that he needs to stay hydrated. Which stage of the disease is Jason currently in?

C

Jason is currently in the period of illness, as he is showing the most severe signs and symptoms. As his body's defense combat the infection, he will start to feel better and enter the period of decline.

What is epidemiology?

Study of where and when diseases occur. How diseases are transmitted

Who is John Snow and why is he important in epidemiology?

• Cholera outbreak 1848-1849

• Mapped cases

• Linked illness to a single water pump

What is descriptive epidemiology?

• Collecting all data to describe the occurrence of the disease

  • Affected individuals

  • Time and location

• Usually retrospective 

What is incidence?

Incidence – number of people who develop a disease during a particular time period

New cases of a disease

What is prevalence?

Prevalence – number of people in a population who have a disease at a specified time regardless of when it first appeared

Accounts for old and new cases

What is a sporadic disease?

Sporadic disease – a disease that occurs only occasionally

What is an endemic disease?

Endemic disease – disease that is constantly present in a population

What is an epidemic?

Epidemic – many people in a given geographic area acquire a disease in a short period of time

What is a pandemic?

A worldwide epidemic

What is analytical epidemiology? What are the 2 methods utilized?

Analysis of a particular disease to determine the probable cause

• Case-control method – compare a group of ill people to an unaffected group; use statistics to determine which factors may have contributed to illness

  • Sick vs. not sick

• Cohort method – compare a group of people who had contact with the agent of disease and one group that has not

  • Exposed vs. not exposed

What is experimental epidemiology?

• Begins with a hypothesis about a particular disease

• Test hypothesis with a group of people

• Example: effectiveness of a drug

Testing the effectiveness of a drug is an example of what type of epidemiology?

Experimental epidemiology: Begins with a hypothesis about a particular disease

Describe the case reporting process for diseases.

• Healthcare workers report specified diseases to identify the chain of transmission.

• Nationally notifiable diseases (must be reported to US Public Health Service)

Including Jason, 261 confirmed Salmonella cases were recorded in 24 states. No single restaurant or restaurant chain was found to be associated with the outbreak. Epidemiologists compared the foods eaten by 53 affected individuals and 53 unaffected individuals in order to determine the source of the infections. What type of study is this? (Select all that apply).

B and E

This is a case-control study. The diets of affected an unaffected individuals were compared to identify the source of the infections. Case-control studies are a type of analytical epidemiology.