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Questions and Answers
What disease is spread primarily via mosquitoes?
What disease is spread primarily via mosquitoes?
Which disease is characterized by a high contagious rate and a majority of the population being vaccinated?
Which disease is characterized by a high contagious rate and a majority of the population being vaccinated?
Which disease is known as a serious and rare illness contracted through animal bites?
Which disease is known as a serious and rare illness contracted through animal bites?
What is the most telling characteristic of herpes infections?
What is the most telling characteristic of herpes infections?
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Which of the following diseases is highly contagious and usually occurs in seasons?
Which of the following diseases is highly contagious and usually occurs in seasons?
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What is the primary role of resident microbiota in the human body?
What is the primary role of resident microbiota in the human body?
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Which factor is NOT typically associated with causing disease?
Which factor is NOT typically associated with causing disease?
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Which of the following defines a pathogen?
Which of the following defines a pathogen?
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How does microbial antagonism protect the host?
How does microbial antagonism protect the host?
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What aspect defines virulence in pathogens?
What aspect defines virulence in pathogens?
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What does the term 'infectious dose (ID50)' refer to?
What does the term 'infectious dose (ID50)' refer to?
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What do opportunistic pathogens require to cause disease?
What do opportunistic pathogens require to cause disease?
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Which of the following is an example of a benefit provided by normal microbiota?
Which of the following is an example of a benefit provided by normal microbiota?
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What does the term 'pathogenesis' specifically refer to?
What does the term 'pathogenesis' specifically refer to?
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Which statement about transient microbiota is correct?
Which statement about transient microbiota is correct?
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What does the incidence of disease measure?
What does the incidence of disease measure?
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Which type of epidemic arises from a single source of infectious agents?
Which type of epidemic arises from a single source of infectious agents?
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What characterizes a pandemic?
What characterizes a pandemic?
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Emerging Infectious Diseases (EIDs) are primarily characterized as:
Emerging Infectious Diseases (EIDs) are primarily characterized as:
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Which term is used to describe occasional cases of a disease reported at irregular intervals?
Which term is used to describe occasional cases of a disease reported at irregular intervals?
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What is the mortality rate a measurement of?
What is the mortality rate a measurement of?
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Which of the following is an example of a re-emerging disease?
Which of the following is an example of a re-emerging disease?
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What does the term 'index case' refer to in epidemiological investigations?
What does the term 'index case' refer to in epidemiological investigations?
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Which factor is NOT considered a contributing factor to emerging infectious diseases?
Which factor is NOT considered a contributing factor to emerging infectious diseases?
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Which of the following diseases is considered endemic to a particular geographic area?
Which of the following diseases is considered endemic to a particular geographic area?
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Which step follows the adhesion process in the establishment of an infection?
Which step follows the adhesion process in the establishment of an infection?
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What type of strategies do pathogens use to evade phagocytes?
What type of strategies do pathogens use to evade phagocytes?
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What is a characteristic of exotoxins compared to endotoxins?
What is a characteristic of exotoxins compared to endotoxins?
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Which type of infection remains localized yet can exert systemic effects through toxins?
Which type of infection remains localized yet can exert systemic effects through toxins?
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What is the primary mode of entering the human body for most pathogenic microbes?
What is the primary mode of entering the human body for most pathogenic microbes?
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In what way do leukocidins function in the pathogen's defense mechanism?
In what way do leukocidins function in the pathogen's defense mechanism?
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What differentiates primary infections from secondary infections?
What differentiates primary infections from secondary infections?
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Which portal of exit do pathogens primarily use to spread through respiratory droplets?
Which portal of exit do pathogens primarily use to spread through respiratory droplets?
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Which of the following best describes the role of quorum sensing in pathogens?
Which of the following best describes the role of quorum sensing in pathogens?
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What is the main function of exoenzymes secreted by infectious agents?
What is the main function of exoenzymes secreted by infectious agents?
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Which of the following statements accurately defines endotoxins?
Which of the following statements accurately defines endotoxins?
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What typically triggers a secondary infection following a primary infection?
What typically triggers a secondary infection following a primary infection?
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What characterizes chronic infections compared to acute infections?
What characterizes chronic infections compared to acute infections?
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Which of the following is a sign that can be objectively measured by a non-patient observer?
Which of the following is a sign that can be objectively measured by a non-patient observer?
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Which type of infection is characterized as asymptomatic or subclinical?
Which type of infection is characterized as asymptomatic or subclinical?
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What term describes the long-term or permanent damage caused by an infectious disease?
What term describes the long-term or permanent damage caused by an infectious disease?
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What is the main difference between a reservoir and a source of infection?
What is the main difference between a reservoir and a source of infection?
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Which type of vector is required for the life cycle of a pathogen?
Which type of vector is required for the life cycle of a pathogen?
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How do horizontal and vertical transmission differ?
How do horizontal and vertical transmission differ?
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Which disease is primarily categorized as noncommunicable?
Which disease is primarily categorized as noncommunicable?
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What is the goal of Koch's postulates in studying infectious diseases?
What is the goal of Koch's postulates in studying infectious diseases?
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What is the most common way to acquire healthcare-associated infections (HAIs)?
What is the most common way to acquire healthcare-associated infections (HAIs)?
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Which of the following pathogens is known to enter a latent stage?
Which of the following pathogens is known to enter a latent stage?
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Which type of carrier is described as not showing any symptoms but can still infect others?
Which type of carrier is described as not showing any symptoms but can still infect others?
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Which statement about zoonotic infections is incorrect?
Which statement about zoonotic infections is incorrect?
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What is an example of indirect transmission through vehicles?
What is an example of indirect transmission through vehicles?
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Study Notes
Health and Disease
- Colonization describes microbes living on or in the human body. Resident microbiota (normal flora) don't cause disease. They help defend against other pathogens, such as vitamin K. Transient microbiota come and go.
- Infection occurs when pathogenic microbes penetrate host defenses, enter tissues, and multiply.
- Disease is a deviation from normal health, characterized by disruption of body's functions. Factors include infections, genetics, aging, environmental agents, and malfunctions in systems or organs. This leads to infectious disease, a disruption of tissues or organs caused by microbes or their products.
- Pathogens are microbes capable of causing disease. Pathology studies disease, etiology identifies its cause, and pathogenesis explains its development.
Normal Microbiota
- Microbes can cross the placenta during childbirth.
- The gut, skin, eyes, respiratory tract, urogenital system, and other areas are colonized by microbes, some of which are considered resident, and some transient. Some reside in tissues that were previously thought to be sterile, such as lungs, bladder, breast milk, and placenta.
- The human microbiome project sequences biota of humans. Human cells have 21,000 protein-encoding genes; microbes inhabiting humans contain ~8 million. Healthy people harbor many potentially dangerous pathogens, though in low numbers. Studying changes in the microbiome helps in understanding disease.
Pathogens
- True pathogens can cause disease in healthy individuals with normal immune systems.
- Opportunistic pathogens cause disease in compromised hosts (weak immune systems) and when they colonize parts of the body not typically inhabited.
- Virulence describes a pathogen's degree of pathogenicity, indicated by its ability to establish itself in a host and cause damage. Virulence factors are characteristics that enhance pathogenicity, such as contributing to toxin production. Microbes with smaller infectious doses are generally more virulent. An infectious dose is the number of organisms needed to cause disease in 50% of those inoculated; and a lethal dose the number of organisms needed to kill 50% of those inoculated..
Infection Process
- Step 1: Entrance. Microbes enter the body through skin, mucous membranes, or the parenteral route (wounds, punctures).
- Step 2: Attachment. Microbes adhere to host tissues using specific molecules called adhesions to establish themselves.
- Step 3: Surviving host defenses. This stage involves avoiding host immune responses, such as those carried out by phagocytes (white blood cells). Antiphagocytic factors are virulence factors that help microbes avoid phagocytes.
- Step 4: Causing disease. Microbes harm host cells directly through enzymes and toxins or indirectly inducing an excessive host response.
- Step 5: Vacating the host. Pathogens exit the body through various portals like the respiratory tract.
Types of Disease
- Localized. Microbes remain confined to a specific tissue; examples include boils and fungal skin infections.
- Systemic. Infection spreads to multiple sites and tissue fluids; this usually involves the bloodstream and may include viruses, bacteria, and fungi.
- Focal. When an infection spreads to other parts of a body from an initial local infection. Pathogens break loose and spread to other tissues or organs, like streptococcal pharyngitis, which can lead to scarlet fever if not controlled.
- Mixed. Several agents establish disease simultaneously at the infection site.
- Primary. The first infection that occurs.
- Secondary. A second infection occurring in a host compromised by the primary infection. This has a different causative agent.
Acute vs. Chronic Infections
- Acute infections: develop rapidly, have short-lived effects, and include examples like the flu.
- Chronic infections: have a prolonged course and last for extended periods, such as Valley fever.
Disease Patterns
- Endemic: a disease that exhibits relatively steady frequency over long periods in a particular region.
- Epidemic: disease that occurs in a large number of individuals within a community or region in a short period.
- Sporadic. A disease that occurs in scattered cases that are infrequent or irregular.
- Pandemic: an epidemic that spreads across continents.
Reservoirs
- Reservoirs are the primary habitats in the natural world from which outbreaks originate, such as humans, animals, water, or soil.
- Living reservoir: these are mainly animals or humans that serve as sources where pathogens can persist.
- Nonliving reservoirs: environmental sources where some pathogenic agents may reside.
- Passive carriers: individuals or objects containing pathogens, which are then transferred to other hosts.
- Chronic carriers: these individuals have latent infections and transmit pathogens without showing obvious signs or symptoms for a prolonged period.
Transmission
- Horizontal transmission: spread of pathogens through contact or other means between individuals.
- Vertical transmission: transmitted from parent to offspring (e.g., during pregnancy or childbirth.)
- Direct contact: transmission of pathogens via physical contact between infected and uninfected individuals.
- Indirect contact: transmission of pathogens via intermediary objects or vectors.
- Vehicle transmission: pathogens are spread via contaminated inanimate objects, food, water, or air.
- Vector transmission: pathogens are carried by insects and other living vectors, like flies and mosquitoes.
Healthcare-Associated Infections (HAIs)
- Nosocomial infections are those acquired during a hospital stay. These infections result in a variety of methods, including faulty procedures, and contaminated instruments. Factors that contribute include the high number of pathogens present, and the compromised immune systems of patients.
- Iatrogenic infections are HAIs due to medical procedures and treatments.
- Control of HAIs involves reducing pathogens through aseptic techniques and maintaining sterile environments.
Koch's Postulates
- Series of criteria to establish the causative agent of an infectious disease. This includes methods to isolate the agent, and to reproduce the disease using this agent in other animals.
Epidemiology
- Epidemiology studies factors related to the rate, distribution, frequency, and frequency of disease and other health factors in a population. Diseases are studied through rates, incidence and prevalence.
- Reportable diseases: some diseases are required by law or convention to be reported to health authorities.
- Epidemiological statistics: measure of disease prevalence, incidence and mortality.
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Description
Explore the concepts of colonization, infection, and disease in human health. This quiz covers the roles of normal and transient microbiota, as well as the factors that lead to infectious diseases. Understand the definitions and differences between pathogens, pathology, and etiology.
