Chapter 14

Question 1

What is etiology in the context of disease?

Answer 1

Etiology refers to the cause of a disease.

Question 2

How is disease defined when there is a change from a state of health?

Answer 2

Disease is defined as any change from a state of health, where part or all of the body is incapable of performing its normal functions.

Question 3

What is infection?

Answer 3

Infection is the invasion or colonization of the body by a pathogenic microbe.

Question 4

What is the primary cause of death worldwide?

Answer 4

Infectious disease is the primary cause of death worldwide.

Question 5

What are some factors affecting the distribution and composition of the human microbiota?

Answer 5

Factors affecting the distribution and composition of human microbiota include:

• Nutrients,
• Physical
• Chemical factors (temperature, pH, O2, CO2),
• Host defenses (immune system)
• Mechanical factors.

Question 6

What is the role of normal microbiota in protecting the host?

Answer 6

Normal microbiota protect the host by:
* Competing for nutrients
* Producing substances harmful to invading microbes
* Affecting pH and available oxygen

Question 7

There are three types of symbosis depending on the relationship between the microbe and the host. What are the three types?

Answer 7

1. Commensalism: One organism benefits, and the other is unaffected.
2. Mutualism: Both organisms benefit.
3. Parasitism: One organism benefits at the expense of the other.

Question 8

What are opportunistic pathogens, and when do they cause disease?

Answer 8

Opportunistic pathogens do not cause disease in their normal habitat in a healthy person but may do so in a different environment.

Question 9

What are Koch’s postulates, and how are they used to prove the cause of an infectious disease?

Answer 9

Koch’s postulates are a set of criteria used to prove the cause of an infectious disease. They include:

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 disease when inoculated into a healthy, susceptible laboratory animal.
4. The pathogen must be isolated from the inoculated animal and shown to be the original organism.

Question 10

What are some exceptions to Koch’s postulates?

Answer 10

• Some diseases are caused by a variety of microbes (Pneumonia, Meningitis)
• Some pathogens can cause several disease conditions
• Some pathogens cause disease only in humans (HIV)
• Some microbes have never been cultured

Question 11

What scientific theory is Koch’s work related to?

Think about Chapter 1

Answer 11

Germ Theory of Disease.

Question 12

What is the difference between symptoms and signs in the context of disease?

Answer 12

Symptoms are changes in body function that are felt by a patient as a result of a disease, such as pain or malaise.

Signs are changes in the body that can be measured or observed as a result of disease.

Question 13

What is communicable disease and give an example. What is a non-communicable disease?

Answer 13

• A communicable disease is a disease that can be spread from one host to another. They are very dangerous when it becomes a contagious disease, because they easily spread from one host to another. For example, chickenpox is a contagious communicable disease.
• Non-communicable diseases are diseases that do not spread from one host to another, such as tetanus.

Question 14

What is the difference between incidence and prevalence in epidemiology?

Answer 14

• Incidence refers to the frequency of new cases of a disease. Incidence measures how often new cases occur
• Prevalence refers to the frequency of existing cases of the disease. Prevalence measures how widespread the disease is in the population.

Question 15

Differentiate between sporadic, endemic, epidemic, and pandemic diseases.

Answer 15

Sporadic disease occurs only occasionally.
Endemic disease is constantly present in a population.
Epidemic disease is acquired by many people in a given area in a short time.
Pandemic disease is a worldwide epidemic that spreads across continents or even globally.

Question 16

Describe the different types of diseases based on their duration: acute, chronic, subacute, and latent.

Answer 16

Acute disease: Symptoms develop rapidly, but the disease lasts only a short time.
Chronic disease: Symptoms develop slowly.
Subacute disease: Intermediate between acute and chronic.
Latent disease: The causative agent is inactive for a time but then activates and produces symptoms.

Question 17

What is herd immunity, and how does it affect the spread of diseases?

Answer 17

Herd immunity refers to the immunity in most of a population, which limits the spread of outbreaks. It occurs when a sufficient portion of the population becomes immune to a disease through vaccination or previous infections, reducing the number of susceptible individuals.

Question 18

Explain the difference between local infection, systemic infection, and focal infection.

Answer 18

• Local infection: Pathogens are limited to a small area of the body.
• Systemic infection: An infection spreads throughout the body, usually in the bloodstream.
• Focal infection: A systemic infection that began as a local infection and can have multiple sites of infection.

Question 19

What are the different methods that microbes will spread throughout the blood?

Answer 19

• Sepsis is a toxic inflammatory condition that arises from the spread of microbes, especially bacteria or their toxins, from a focus of infection.
• Bacteremia refers to bacteria in the bloodstream,
• Septicemia, also known as blood poisoning, is characterized by the growth of bacteria in the blood.
• Toxemia indicates the presence of toxins in the bloodstream
• Viremia means the presence of viruses in the blood.

Question 20

What is the differene between a primary infection and a secondary infection? Provide examples of each.

Answer 20

• A primary infection is an acute infection that causes the initial illness, such as strep throat.
• A secondary infection is an opportunistic infection that occurs after a primary (predisposing) infection. Examples include Pneumocystis infection and sinus infection.

Question 21

What is a subclinical disease, and can you provide examples of it?

Answer 21

Subclinical disease is a condition with no noticeable signs or symptoms, often referred to as an inapparent infection.

Examples include Streptococcus pyogenes carriers, individuals carrying the polio virus, or the hepatitis A virus without displaying symptoms.

Question 22

What are some factors that can make the body more susceptible to disease?

Answer 22

Various factors can increase susceptibility to disease, including gender, inherited traits (like the sickle cell gene), climate and weather conditions, lack of vaccination, fatigue, age, lifestyle choices, nutrition, and the effects of chemotherapy.

Question 23

Describe the typical sequence of events that occur during infection and disease. List the five periods of infection.

Answer 23

1. Incubation period: Interval between the initial infection and any signs or symptoms.
2. Prodromal period: Early mild symptoms of disease, often characterized by general aches and malaise.
3. Illness period: The most severe phase of the disease with pronounced signs and symptoms.
4. Decline period: Signs and symptoms subside, and the patient may recover.
5. Convalescence period: The patient regains strength.

Able to spread illness at any stage. You are subject to reinfection at the Decline period.

Question 24

Explain the concept of reservoirs in the context of disease transmission. What are some examples of reservoirs?

Answer 24

Reservoirs are continual sources of infection. They include:
* Human reservoirs, where carriers may have inapparent infections or latent diseases.
* Animal reservoirs, contributing to zoonoses (diseases transmitted from animals to humans).
* Nonliving reservoirs, such as soil and water, that can carry disease agents.

Question 25

What are the principle routes of transmission for infectious diseases?

Answer 25

The three principle routes of transmission for infectious diseases are:
1. Contact
2. Vehicles
3. Vectors

Question 26

What are the three ways of spreading disease through contact transmission?

Answer 26

1. Direct Transmission (Touching, kissing, sex)
2. Indirect Transmission (Bedding, Towels, Tissues)
3. Droplet Transmission (Sneezing, Coughing, Laughing)

Question 27

What is direct contact transmission? Provide examples of diseases transmitted through direct contact.

Answer 27

Direct contact transmission involves the transfer of pathogens from one person to another through physical contact.

Examples include diseases like the common cold, influenza, staphylococcal infections, scarlet fever, and sexually transmitted infections (STIs).

Question 28

What is indirect contact transmission, and how does it occur? Give examples of diseases transmitted through indirect contact.

Answer 28

Indirect contact transmission involves the transfer of pathogens via nonliving objects (fomites).

It can occur through contaminated items such as stethoscopes, tissues, bedding, towels, or even contaminated syringes. Diseases like AIDS and hepatitis B can be transmitted through indirect contact.

Question 29

What is droplet transmission, and what are the common methods of droplet transmission?

Answer 29

Droplet transmission involves the spread of microbes in mucus droplets when an infected person coughs, sneezes, laughs, or talks. These droplets can contain pathogens and are the primary means of transmission for diseases like influenza, pneumonia, and whooping cough

Question 30

What is vehicle transmission and what three examples of vehicle transmission?

Answer 30

Vehicle tranmission is the spread of disease agents through a medium.
1. Air
2. Water
3. Food

Question 31

How do diseases transmit through air, and can you provide examples of diseases transmitted through the airborne route?

Answer 31

Airborne transmission occurs when microbes travel more than 1 meter through the air. Diseases like tuberculosis and the measles virus are commonly transmitted through this route. Additionally, dust particles may carry streptococci and staphylococci, while spores can carry fungal pathogens.

Question 32

What is waterborne transmission, and provide examples of diseases transmitted through contaminated water.

Answer 32

Waterborne transmission occurs when diseases are spread through untreated or poorly treated sewage. Examples include cholera, shigellosis, and leptospirosis, which are caused by pathogens that enter the water supply through contaminated sewage.

Question 33

How do diseases transmit through foodborne transmission? Give examples of diseases transmitted through contaminated food.

Answer 33

Foodborne transmission occurs when diseases are spread through the consumption of contaminated food. Common examples include food poisoning, infections with pathogenic bacteria like Salmonella, or infestations by parasites like tapeworms.

Question 34

What are vectors in the context of disease transmission, and how do they contribute to the spread of diseases?

Answer 34

Vectors are animals, often arthropods, that carry pathogens from one host to another. There are two main types of transmission by vectors:

• Mechanical transmission, where the vector passively transports pathogens on its body parts.
• Biological transmission, which is an active process involving the vector biting an infected host, ingesting infected blood, and transmitting the pathogens. Examples of vectors include ticks and mosquitoes.

Question 35

What is a nosocomial infection, and what factors contribute to its occurrence?

Answer 35

Nosocomial infections, also known as healthcare-associated infections (HAIs), are infections that result from microorganisms in the hospital environment.

Several factors contribute to their occurrence, including the weakened (compromised) status of the host, the presence of microorganisms in the hospital environment, and the chain of transmission within the hospital setting.

Question 36

What are some examples of microbes that cause nonsocomial infections?

Answer 36

Question 37

What is herd immunity? How does it impact the spread of diseases?

Answer 37

Herd immunity refers to immunity in a large part of the population. When a significant portion of a population becomes immune to a disease, it limits the spread of that disease. Outbreaks are limited due to the reduced number of susceptible individuals. Factors contributing to this include vaccination and a lack of vulnerable individuals, such as unvaccinated children.