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Questions and Answers
What distinguishes infectious diseases from non-infectious diseases?
What distinguishes infectious diseases from non-infectious diseases?
Which of the following is considered a non-infectious disease?
Which of the following is considered a non-infectious disease?
What is meant by pathogenicity in the context of infectious diseases?
What is meant by pathogenicity in the context of infectious diseases?
What is the main characteristic of a virus that allows it to replicate?
What is the main characteristic of a virus that allows it to replicate?
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During which phase is a disease transmissible to others?
During which phase is a disease transmissible to others?
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Which of the following pathogens is NOT categorized as an infectious disease?
Which of the following pathogens is NOT categorized as an infectious disease?
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What is a virion?
What is a virion?
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Which of the following is a correct sequence of virus infection steps?
Which of the following is a correct sequence of virus infection steps?
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Which of the following viruses is an example of a DNA virus?
Which of the following viruses is an example of a DNA virus?
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What is a characteristic of RNA viruses that makes them particularly challenging to manage?
What is a characteristic of RNA viruses that makes them particularly challenging to manage?
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What type of viruses evade the immune system by down regulating MHC?
What type of viruses evade the immune system by down regulating MHC?
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What is one of the methods for treating viral infections?
What is one of the methods for treating viral infections?
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What role do commensal bacteria play in health?
What role do commensal bacteria play in health?
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What is a common outcome of immune cell memory being ineffective against RNA viruses?
What is a common outcome of immune cell memory being ineffective against RNA viruses?
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What is the primary purpose of gram staining in a clinical setting?
What is the primary purpose of gram staining in a clinical setting?
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Which type of viruses are known to be zoonotic?
Which type of viruses are known to be zoonotic?
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What type of disease is caused by pathogens?
What type of disease is caused by pathogens?
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Which of the following is a characteristic of a virus?
Which of the following is a characteristic of a virus?
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What allows viruses to evade the immune system effectively?
What allows viruses to evade the immune system effectively?
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Which phase describes the period before the disease becomes transmissible?
Which phase describes the period before the disease becomes transmissible?
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What is one of the main characteristics of Type A infection compared to Type B infection?
What is one of the main characteristics of Type A infection compared to Type B infection?
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What happens during the latency period of a viral infection?
What happens during the latency period of a viral infection?
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Which category includes the pathogens responsible for causing malaria?
Which category includes the pathogens responsible for causing malaria?
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What occurs during the release phase of a viral infection?
What occurs during the release phase of a viral infection?
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What makes RNA viruses particularly problematic in terms of immune response?
What makes RNA viruses particularly problematic in terms of immune response?
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Which of the following are examples of DNA viruses?
Which of the following are examples of DNA viruses?
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What is one of the main reasons new vaccines for RNA viruses need to be regularly developed?
What is one of the main reasons new vaccines for RNA viruses need to be regularly developed?
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How do herpes viruses manage to evade the immune system?
How do herpes viruses manage to evade the immune system?
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What is a significant function of commensal bacteria in the gut?
What is a significant function of commensal bacteria in the gut?
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What type of therapy is typically used for managing viral infections?
What type of therapy is typically used for managing viral infections?
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Why is gram staining an important procedure in clinical settings?
Why is gram staining an important procedure in clinical settings?
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Why are many pox viruses categorized as zoonotic?
Why are many pox viruses categorized as zoonotic?
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What characteristic of RNA viruses contributes to their ability to frequently change their antigen structure?
What characteristic of RNA viruses contributes to their ability to frequently change their antigen structure?
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Which of the following is a reason why new vaccines for RNA viruses need to be developed regularly?
Which of the following is a reason why new vaccines for RNA viruses need to be developed regularly?
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Which virus category is known for having a significant number of zoonotic members?
Which virus category is known for having a significant number of zoonotic members?
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Which statement accurately describes the nature of viruses?
Which statement accurately describes the nature of viruses?
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What is one of the main challenges in developing treatment strategies for RNA viruses?
What is one of the main challenges in developing treatment strategies for RNA viruses?
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What is implied by the term 'contagious' in relation to diseases?
What is implied by the term 'contagious' in relation to diseases?
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Which type of virus is known to down regulate MHC as a mechanism to evade the immune system?
Which type of virus is known to down regulate MHC as a mechanism to evade the immune system?
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During which phase does a viral infection primarily utilize the host cell's machinery for replication?
During which phase does a viral infection primarily utilize the host cell's machinery for replication?
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What differentiates pathogenic from non-pathogenic organisms?
What differentiates pathogenic from non-pathogenic organisms?
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Which of the following statements about gram staining is accurate?
Which of the following statements about gram staining is accurate?
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What is a critical factor that makes enveloped viruses easier to eliminate compared to non-enveloped viruses?
What is a critical factor that makes enveloped viruses easier to eliminate compared to non-enveloped viruses?
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What role do commensal bacteria play in the health of the gut?
What role do commensal bacteria play in the health of the gut?
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What describes a characteristic of commensal bacteria in the context of health?
What describes a characteristic of commensal bacteria in the context of health?
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What is one effective method for promoting herd immunity against viral infections?
What is one effective method for promoting herd immunity against viral infections?
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Which infectious disease category is responsible for causing infections like athlete's foot?
Which infectious disease category is responsible for causing infections like athlete's foot?
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Which of these statements about the immune system's memory in relation to RNA viruses is accurate?
Which of these statements about the immune system's memory in relation to RNA viruses is accurate?
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Study Notes
Infectious and Non-Infectious disease
- Infectious disease is caused by pathogens, like influenza.
- Non-infectious disease is caused by factors other than pathogens, like cancer.
- Pathogenicity refers to the ability of a pathogen to cause disease.
- Transmissible (Contagious) implies a disease can spread from person to person, directly or indirectly.
How Infection Develops
- Preclinical phase (incubation period): the time between exposure and the onset of symptoms
- Infectious period: the time when a disease is contagious and can be transmitted.
Two Types of Infection
- Type A infection: the infection is present in the body, but there are no symptoms.
- Type B infection: The infection is present in the body and the host is experiencing symptoms.
The Immune System
- The immune system plays a key role in how we feel when we are sick.
- The immune system reacts to viruses, bacteria, fungi, and parasites.
Viruses
- Viruses are the most abundant biological entities on Earth.
- A virus consists of a protein coat (capsid), an envelope (not always), and a core of DNA or RNA.
- Viruses require a host cell (bacteria, animal, or plant) to replicate.
- Most viruses are pathogenic, meaning they cause disease.
- A single viral particle is called a virion.
Viral Structure
- Enveloped viruses are easier to kill with alcohol.
- The structure of a virus helps it evade the immune system and resist destruction.
- Non-enveloped viruses have a tougher protein coat and are harder to destroy.
Viral Replication
- Step 1: Entry - the virus binds to the host cell and enters.
- Step 2: Release of DNA or RNA - the virus releases its genetic material inside the host cell.
- Step 3: Hijacking host cell machinery for replication - The virus uses the host cell's resources to replicate its own viral parts.
- Step 4: Latency period - The virus may remain dormant within the host cell.
- Step 5: Shedding of viral particles - New virus particles are released from the host cell.
DNA Virus Examples
- Poxviruses: such as cowpox, monkeypox, smallpox, and myxoma virus. Many are zoonotic.
- Parvoviruses: infect a variety of hosts, including dogs, pigs, humans, rats, and ferrets.
- Herpesviruses: infect practically every species and are considered endemic. Herpesviruses evade the immune system by downregulating MHC.
RNA Virus Examples
- Rhabdoviruses: cause rabies.
- Coronaviruses: caused COVID-19.
- Retroviruses: include FIV (Feline Immunodeficiency Virus) and Avian Influenza.
Why RNA Viruses are Problematic
- Mutation: RNA viruses mutate frequently, making them difficult to target with vaccines and treatments.
- Genome Reassortment: RNA viruses can exchange genetic information between strains, leading to new and potentially more dangerous variants.
Treatment and Prevention of Viral Infection
- Supportive therapy: focuses on managing symptoms and supporting the body's natural defenses.
- Antivirals: medications that can sometimes target specific viral processes.
- Vaccination: aims to stimulate the body's immune system to recognize and fight off a specific virus.
- Herd immunity: occurs when a significant portion of a population is immune to a disease, making it difficult for it to spread.
- Good management: includes hygiene practices, quarantine, and isolation to prevent transmission.
Bacteria: Prokaryotes
- Single-celled organisms that lack a nucleus, mitochondria, or other membrane-bound organelles.
- Free-living.
- Fewer than 100 species known to cause disease.
- Many bacteria live in symbiosis with us as commensals, aiding in our overall health.
The Importance of Bacteria
- Bacteria in the rumen of cattle, sheep, and goats, and the caecum of horses and rabbits, are essential for breaking down cellulose.
- Bacteria in the gut and immune system play a crucial role in maintaining healthy function.
Bacterial Morphology
- Bacteria come in various shapes:
- Cocci (spherical)
- Bacilli (rod-shaped)
- Spirilla (spiral-shaped)
- Bacteria can also be classified by their arrangement:
- Staphylococcus: clustered cocci
- Streptococcus: chain-like cocci
- Diplococcus: pairs of cocci
- The arrangement and morphology of bacteria can be used for identification.
Gram Staining
- Gram staining is a rapid diagnostic test used to identify bacteria.
- The test differentiates bacteria into two groups:
- Gram-positive bacteria: retain the violet dye used in the staining process.
- Gram-negative bacteria: do not retain the violet dye, appearing reddish-pink under a microscope.
The Importance of Gram Staining
- Gram staining is important for:
- Rapid identification of bacteria.
- Determining the appropriate antibiotic treatment.
- Monitoring the effectiveness of antibiotic therapy.
- Understanding the nature of bacterial infections.
Infectious & Non-infectious Diseases
- Infectious disease: Illness caused by pathogens. Examples: influenza.
- Non-infectious disease: Illness caused by factors other than pathogens. Examples: cancer.
- Pathogenicity: Ability of a pathogen to cause disease. Example: Commensal bacteria are non-pathogenic while E. coli O157 is highly pathogenic.
- Transmissible (contagious): Ability to spread from one individual to another.
Infectious Disease Processes
- Infectious period: When disease is transmissible.
- Preclinical phase: Also known as the incubation period.
- Two types of infection: Type A and Type B.
The Immune System
- Part of how you feel when sick is due to your immune system.
- Viruses, bacteria, fungi, and parasites are all pathogens that can trigger the immune response.
Viruses
- Most abundant biological entities on earth.
- Consist of a protein coat (capsid), envelope (not all), core of DNA or RNA.
- Require a host cell to replicate (bacteria, animal or plant).
- Most viruses cause disease.
- Each particle is called a "virion".
- Structure of virus helps evade immune system and resist destruction.
- Enveloped viruses are easier to kill with alcohol.
Viral Infection Stages
- Entry: The virus enters the host cell.
- Release DNA or RNA: The virus releases its genetic material into the host cell.
- Hijack host cell machinery for replication: The virus uses the host cell's resources to replicate itself.
- Latency period: The virus may remain dormant within the host.
- Shedding of viral particles: New viral particles are released from the host cell.
DNA Virus Examples
- Pox viruses: Cow pox, monkey pox, small pox, myxoma virus (many are zoonotic).
- Parvo viruses: Can infect a variety of hosts including dogs, pigs, humans, rats, ferrets.
- Herpes viruses: Infects almost every species and considered "endemic" (evades the immune system by down regulating MHC).
RNA Virus Examples
- Rhabdoviruses: Rabies
- Corona viruses: Covid-19
- Retrovirus: FIV, Avian influenza
RNA Viruses: Challenges
- RNA viruses are problematic due to their "shapeshifter" nature: Genome mutation and genome reassortment.
- Immune cell memory is ineffective because the antigen changes frequently.
- New vaccines need to be developed, not always feasible.
Treatment and Prevention of Viral Infection
- Supportive therapy: Assists with symptoms.
- Anti-virals: Medications that target specific viruses.
- Vaccination: Induces immunity and provides herd immunity.
- Good management: Practices that help prevent the spread of viruses, such as hygiene and sanitation.
Bacteria
- Prokaryotic: Single-celled organisms that lack a nucleus, mitochondria, or other membrane-bound organelles.
- Free living: Can exist independently.
- Fewer than 100 species known to cause disease.
- Commensal: Most bacteria live symbiotically with humans.
Importance of Bacteria
- Commensal bacteria are required in the rumen of cattle, sheep, and goats and the caecum of horses and rabbits to break down cellulose.
- Essential for the normal function of the gut and immune system.
Gram Staining
- Important for quick identification of bacteria in clinical settings.
- A staining technique that distinguishes bacteria based on their cell wall structure.
Infectious vs Non-Infectious Diseases
- Infectious diseases are caused by pathogens, such as bacteria, viruses, fungi, and parasites.
- Non-infectious diseases are caused by factors other than pathogens, such as genetics, environmental factors, or lifestyle choices.
- Pathogenicity refers to the ability of a pathogen to cause disease.
- Transmissible or contagious diseases can be spread from one person to another.
Infectious Disease Development
- Preclinical phase or incubation period: the time between exposure to a pathogen and the onset of symptoms.
- Infectious period: the time when a person is contagious and can spread the disease.
Types of Infection
- Type A infection: characterized by a rapid onset of symptoms and a short duration.
- Type B infection: characterized by a slower onset of symptoms and a longer duration; can lead to chronic illness.
Immune System and Infectious Disease
- The immune system plays a crucial role in fighting off infections.
- When the immune system is compromised, the body is more susceptible to disease.
Viruses
- Viruses are the most abundant biological entities on earth.
- They consist of a protein coat (capsid), an envelope (not all), and a core of DNA or RNA.
- Viruses require a host cell to replicate.
- Most viruses cause disease; they are not commensal.
- Each viral particle is called a "virion."
- The structure of a virus helps it evade the immune system and resist destruction. Enveloped viruses are easier to kill with alcohol.
Virus Replication Cycle
- Entry: The virus enters the host cell.
- Release of DNA/RNA: The virus releases its genetic material into the host cell.
- Hijacking host cell machinery: The virus uses the host cell’s machinery to replicate its own DNA or RNA.
- Latency period: The virus remains dormant within the host cell.
- Shedding of viral particles: The virus produces new viral particles, which are released from the host cell and can infect other cells.
Examples of DNA Viruses
- Pox viruses: Cow pox, monkeypox, smallpox, myxoma virus (many are zoonotic).
- Parvo viruses: Can infect a variety of hosts, including dogs, pigs, humans, rats, and ferrets.
- Herpes viruses: Infect almost every species and are considered "endemic." They can evade the immune system by down-regulating MHC.
Examples of RNA Viruses
- Rhabdoviruses: Rabies.
- Corona viruses: COVID-19.
- Retroviruses: FIV (feline immunodeficiency virus), Avian influenza.
Challenges with RNA Viruses
- RNA viruses are "shapeshifters." They exhibit genome mutation and genome reassortment.
- This makes it difficult for the immune system to remember the virus and mount an effective response.
- New vaccines may be needed frequently to address evolving viral strains.
Treatment and Prevention of Viral Infection
- Supportive therapy: Provides symptomatic relief.
- Anti-virals: Some anti-viral medications can target specific viral proteins or processes.
- Vaccination: Stimulates the immune system to develop antibodies against the virus, providing immunity and reducing the risk of infection.
- Herd immunity: Occurs when a large proportion of the population is immune to a virus, making it difficult for the virus to spread.
- Good management: Maintaining good hygiene practices, such as handwashing, can prevent the spread of viruses.
Bacteria
- Prokaryotic: Single-celled organisms that lack a nucleus, mitochondria, or other membrane-bound organelles.
- Free living: Most bacteria are not pathogenic.
- Commensal: Many bacteria live in a symbiotic relationship with humans and other organisms, providing benefits to their host.
- Pathogenic: Fewer than 100 bacterial species are known to cause disease.
Importance of Bacteria
- Bacteria are essential for health.
- They play important roles in digestion, nutrient cycling, and immune system development.
- Commensal bacteria are required in the rumen of cattle, sheep, and goats and the caecum of horses and rabbits to break down cellulose.
- Bacteria are essential for the normal function of the gut and immune system.
Bacterial Structure and Function
- Cell wall: Provides structural support and protection for the bacteria.
- Cytoplasm: Contains the genetic material of the bacteria.
- Ribosomes: Involved in protein synthesis.
- Flagella: Help bacteria move.
- Pili: Help bacteria attach to surfaces.
- Capsule: A protective layer that can help bacteria evade the immune system.
Bacterial Reproduction
- Bacteria reproduce asexually through binary fission.
- One bacterial cell divides into two identical daughter cells.
Bacterial Disease
- Exotoxins: Toxic proteins released by bacteria that can harm host cells.
- Endotoxins: Components of bacterial cell walls that can trigger an inflammatory response in the host.
Gram Staining
- Gram staining is a technique used to classify bacteria based on their cell wall structure.
- Gram-positive bacteria: Have a thick peptidoglycan layer in their cell wall. They stain purple.
- Gram-negative bacteria: Have a thinner peptidoglycan layer and an outer membrane. They stain pink.
Significance of Gram Staining
- Gram staining allows for rapid identification of bacteria in a clinical setting.
- This information can help guide treatment decisions and prevent the spread of infection.
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Description
Explore the differences between infectious and non-infectious diseases in this quiz. Learn about how infections develop, the types of infections, and the role of the immune system. Test your knowledge on pathogens and their impact on health.
