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Microbiology and Parasitology > Introduction to Viruses > Flashcards

Introduction to Viruses Flashcards

1
Q

__________ include viruses that are difficult to detect or study.

A

Elusive virus

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2
Q

UNDER THE SEARCH FOR THE ELUSIVE VIRUS

  • He postulated/suggested that rabies was caused by a virus (1884).
A

Louis Pasteur

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3
Q

UNDER THE SEARCH FOR THE ELUSIVE VIRUS

  • They showed a disease in tobacco was caused by a virus (1890s).
A

Ivanovski and Beijerinck

Note:

  • Dmitri Ivanovski and Martinus Beijerinck demonstrated that a disease affecting tobacco plants (later known as tobacco mosaic disease) was caused by an agent that could pass through filters fine enough to block bacteria.
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4
Q

In 1950s, virology was multifaceted scientific discipline, combining biology, chemistry, and medicine to study viruses.

  • _________ were defined as noncellular particles with a definite size, shape, and chemical composition.
A

Viruses

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5
Q

There is ___________ on how and when viruses originated.

A

no universal agreement

ADD:

  • Some theories suggest they evolved from cellular organisms, while others propose they emerged from genetic elements that escaped from cells.
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6
Q

Viruses are considered the most _________ microbes on Earth.

A

abundant

ADD:

  • They exist in every environment, including extreme conditions, and outnumber all other forms of life combined.
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7
Q

Viruses have influenced the evolution of these 3. What are these?

A

Bacteria, Archaea, and Eukarya

ADD:

  • This has contributed to genetic diversity and the development of new traits in different species.
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8
Q

Viruses cannot reproduce independently and must infect a host cell to replicate.

Hence, they are called _______________.

A

Obligate intracellular parasites

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9
Q

FAMILIARIZE ONLY!

“PROPERTIES OF VIRUSES”

A
  • Obligate intracellular parasites of bacteria, protozoa, fungi, algae, plants, and animals
  • Ultramicroscopic size, ranging from 20 nm up to 450 nm (diameter)
  • Not cellular in nature; structure is very compact and economical
  • Do not independently fulfill the characteristics of life
  • Inactive macromolecules outside the host cell and active only inside host cells.
  • Basic structure consists of protein shell (capsid) surrounding nucleic acid core.
  • Nucleic acid can be either DNA or RNA but not both.
  • Nucleic acid can be double-stranded DNA, single-stranded DNA, single-stranded RNA, or double-stranded RNA.
  • Molecules on virus surface impart high specificity for attachment to host cell
  • Multiply by taking control of host cell’s genetic material and regulating the synthesis and assembly of new viruses
  • Lack enzymes for most metabolic processes
  • Lack machinery for synthesizing proteins
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10
Q

Viruses are extremely small, with most measuring ________ in diameter.

A

less than 0.2 (μm)

Note:

  • Due to their size, they cannot be seen with a light microscope and require an electron microscope for detailed visualization.
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11
Q

FAMILIARIZE ONLY!

“Viral Structure”

A

No Resemblance to Cells

  • Viruses are not cellular and lack organelles like ribosomes, mitochondria, and a nucleus.
  • They cannot synthesize proteins on their own, relying entirely on a host cell for replication.

Minimalist Design for Infection

Viruses contain only the essential components needed to invade and control a host cell:

  • Genetic material (either DNA or RNA, but never both)
  • Capsid (a protein coat that protects the genetic material)
  • Some viruses also have an envelope (a lipid membrane derived from the host cell) that aids in infection.
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12
Q

GENERAL STRUCTURE OF VIRUSES:

  • All viruses have a ________, this is their protein coat that enclose and protect their nucleic acid (DNA or RNA).
A

capsid

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13
Q

GENERAL STRUCTURE OF VIRUSES:

  • The capsid + nucleic acid together form the _________.
A

nucleocapsid

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14
Q

GENERAL STRUCTURE OF VIRUSES:

  • Some viruses have an __________, an external lipid membrane derived from the host cell.
A

envelope

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15
Q

GENERAL STRUCTURE OF VIRUSES:

  • Viruses without an envelope are called ___________.
A

naked viruses

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16
Q

GENERAL STRUCTURE OF VIRUSES:

  • The capsid is made up of identical (repeating) protein subunits called ___________, which self-assemble into specific shapes.
A

capsomers

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17
Q

What are the 2 Structural Capsid Types?

A
  • Helical
  • Icosahedral
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18
Q

UNDER GENERAL STRUCTURE OF VIRUSES

  • It is a continuous helix of capsomers forming a cylindrical nucleocapsid.
A

Helical or Helical capsid

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19
Q

UNDER GENERAL STRUCTURE OF VIRUSES

  • Has 20 triangular faces and 12 corners, forming a symmetrical geometric shape.
A

Icosahedral or Icosahedral Capsid

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20
Q

UNDER GENERAL STRUCTURE OF VIRUSES

  • Mostly animal viruses
  • Acquired when the virus leaves the host cell
  • Exposed proteins on the outside of the envelope, called spikes, are essential for attachment of the virus to the host cell.
A

Viral envelope

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21
Q

The ff are the functions of _____________.

  • Protects the nucleic acid when the virus is outside of the host cell.
  • Helps the virus bind to a cell surface and assists the penetration of the viral DNA or RNA into a suitable host cell.
A

Capsid/Envelope

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22
Q

Under GENERAL STRUCTURE OF VIRUSES – Complex Viruses

  • Do not have a typical capsid structure.
  • Instead, they are covered by a dense layer of lipoproteins
A

Poxviruses (Atypical Viruses)

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23
Q

Under GENERAL STRUCTURE OF VIRUSES – Complex Viruses

  • Have a polyhedral (icosahedral) nucleocapsid.
  • Possess a helical tail and attachment fibers used to bind and inject genetic material into bacterial cells.
A

Bacteriophages (Viruses that Infect Bacteria)

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24
Q

FAMILIARIZE ONLY!

“Viral Nucleic Acids”

A

Viral Genome

  • A virus contains either DNA or RNA, never both.
  • The genome carries essential genes for infecting a host cell and taking control of its machinery to produce new viruses.
  • The number of genes varies significantly among viruses, ranging from a few to hundreds.

DNA Viruses

  • Usually double-stranded (dsDNA) but can also be single-stranded (ssDNA).
  • The DNA can be circular or linear.

RNA Viruses

  • Usually single-stranded (ssRNA) but can also be double-stranded (dsRNA).
  • Some RNA viruses have segmented genomes, meaning their genetic material is divided into separate RNA pieces.

Types of ssRNA viruses:

  • Positive-sense RNA (+ssRNA): Can be directly translated into proteins.
  • Negative-sense RNA (−ssRNA): Must be converted into a readable form (mRNA) before translation.
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25
Q

WHAT IS THIS?

  • ssRNA genomes ready for immediate translation are called __________.
A

positive-sense RNA

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26
Q

WHAT IS THIS?

  • ssRNA genomes that must be converted into proper form are called __________.
A

negative-sense RNA

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27
Q

Some viruses carry their own enzymes to assist in replication because they lack the cellular machinery needed for nucleic acid synthesis.

What are the (3) Viral Enzymes or Pre-formed enzymes?

A
  • Polymerases
  • Replicases
  • Reverse Transcriptase

NOTE:

  • These enzymes help viruses replicate inside host cells by facilitating nucleic acid synthesis and genome replication.
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28
Q

What enzyme is this?

  • Enzymes that synthesize DNA or RNA based on the virus’s genetic material.
A

Polymerases

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29
Q

What enzyme is this?

  • Enzymes that copy RNA to make more viral RNA.
A

Replicases

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30
Q

What enzyme is this?

  • An enzyme that synthesizes DNA from an RNA template.
  • Essential for AIDS virus to integrate their genetic material into the host genome.
A

Reverse Transcriptase

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31
Q

Viruses are classified based on these three. What are these?

A
  • Structure (capsid shape, presence of envelope)
  • Chemical composition (type of nucleic acid: DNA or RNA)
  • Genetic makeup (single-stranded vs. double-stranded, segmented vs. non-segmented)
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32
Q

In Current Viral Taxonomy, how many of the ff are currently recognized?

  • (a)___ orders
  • (b)___ families (end in -viridae)
  • (c)___ genera (end in -virus)

Note: (There are 3 answers)

A
  • (a) 3
  • (b) 63
  • (c) 263
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33
Q

Under How Viruses Are Classified

  • Family name ends in ________?
A

-viridae

Example: Herpesviridae

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34
Q

Under How Viruses Are Classified

  • Genus name ends in _______?
A

-virus

Example: Simplexvirus

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35
Q

Under How Viruses Are Classified

  • What species example is HSV-I?
A

Herpes Simplex Virus I

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36
Q

What are the 6 Phases in Animal Virus Multiplication Cycle?

A
  • Adsorption
  • Penetration
  • Uncoating
  • Synthesis
  • Assembly
  • Release

Remember the acronym APUSAR

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37
Q

Under ANIMAL VIRUS MULTIPLICATION

  • Binding of virus to specific molecules on the host cell.
A

Adsorption

Note:

  • The virus attaches to its host cell by specific binding of its spikes to cell receptors.
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38
Q

Under ANIMAL VIRUS MULTIPLICATION

  • Genome enters the host cell.
A

Penetration

Note:

  • The virus is engulfed into a vesicle and its envelope.
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39
Q

Under ANIMAL VIRUS MULTIPLICATION

  • The viral nucleic acid is released from the capsid.
A

Uncoating

Note:

  • Freeing the viral RNA into the cell cytoplasm
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40
Q

Under ANIMAL VIRUS MULTIPLICATION

  • Viral components are produced.
A

Synthesis

Note:

  • Under the control of viral genes, the cell synthesizes the basic components of new viruses: RNA molecules, capsomers, spikes.
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41
Q

Under ANIMAL VIRUS MULTIPLICATION

  • New viral particles are constructed.
A

Assembly

Note:

  • Viral spike proteins are inserted into the cell membrane for the viral envelope; nucleocapsid is formed from RNA and capsomers.
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42
Q

Under ANIMAL VIRUS MULTIPLICATION

  • Assembled viruses are released by budding (exocytosis) or cell lysis
A

Release

Note:

  • Enveloped viruses bud off of the membrane, carrying away an envelope with the spikes. This complete virus or virion is ready to infect another cell.
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43
Q

WHAT IS THIS?

  • A virus randomly collides with a susceptible host cell.
  • It binds specifically to receptor sites on the host cell membrane.
  • This interaction determines which cells a virus can infect.
A

Adsorption (Attachment)

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44
Q

What are the 3 Host Range (Types of Cells a Virus Can Infect)?

A
  • Narrow Host Range
  • Moderate Host Range
  • Broad Host Range
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45
Q

This is an example of Narrow Host Range where it infects only specific cells in a species.

  • Infects only human liver cells.

What is this?

A

Hepatitis B

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46
Q

This is an example of Moderate Host Range where it infects a limited group of species.

  • Infects primate intestinal and nerve cells.

What is this?

A

Poliovirus

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47
Q

This is an example of Broad Host Range where it infects many species.

  • Infects various cells of many mammals.

What is this?

A

Rabies virus

48
Q

After adsorption, the virus enters the host cell through one of two main methods. What are these?

A
  • Endocytosis (Engulfment)
  • Fusion (Membrane Merging)
49
Q

WHAT IS THIS?

  • This is the process where an entire virus is engulfed and enclosed in a vacuole or vesicle.
A

Endocytosis

50
Q

WHAT IS THIS?

  • This is where an envelope merges directly with membrane resulting in nucleocapsid’s entry into cytoplasm.
51
Q

Once new viruses are assembled, they exit the host cell in one of two ways. What are these?

A

Budding and Lysis

52
Q

WHAT IS THIS?

  • The nucleocapsid binds to the host cell membrane.
  • The virus gains an envelope from the host’s membrane as it is released.
  • The host cell remains alive longer, releasing viruses gradually.
A

Budding (Exocytosis)

53
Q

WHAT IS THIS?

  • Non-enveloped and complex viruses cause the host cell to burst when it is full of newly assembled viruses.
  • The host cell dies immediately.
A

Lysis (Cell Rupture)

54
Q

WHAT IS THIS?

  • These are virus-induced damage that alters host cells. These changes can be observed under a microscope and are often used to identify viral infections.
A

Cytophathic effects (CPEs)

55
Q

FAMILIARIZE ONLY!

“What are the Types of Cytopathic Effects”

A

Changes in Size and Shape

  • Infected cells may become enlarged, shrunken, or deformed.

Cytoplasmic Inclusion Bodies

  • Abnormal clusters of viral proteins or nucleic acids appear in the cytoplasm.

Inclusion Bodies

  • Compact masses of viruses or damaged cell organelles inside the cell.

Syncytia Formation (Multinucleated Cells)

  • Infected cells fuse together, forming large multinucleated cells (syncytia).

Cell Lysis (Destruction)

  • Viruses rupture the host cell, releasing viral particles.

Alteration of Host DNA

  • Some viruses insert their genetic material into the host’s DNA, disrupting normal functions.

Transformation into Cancerous Cells

  • Some viruses cause uncontrolled cell growth, leading to tumors and cancer.
56
Q

Determine which virus is this based on the Response in Animal Cell.

  • Cell round up; inclusions appear in cytoplasm.
A

Smallpox virus

57
Q

Determine which virus is this based on the Response in Animal Cell.

  • Cells fuse to form multinucleated syncytia; nuclear inclusions.
A

Herpes simplex

58
Q

Determine which virus is this based on the Response in Animal Cell.

  • Clumping of cells; nuclear inclusions.
A

Adenovirus

59
Q

Determine which virus is this based on the Response in Animal Cell.

  • Cell lysis; no inclusions.
A

Poliovirus

60
Q

Determine which virus is this based on the Response in Animal Cell.

  • Cell enlargement; vacuoles and inclusions in cytoplasm.
61
Q

Determine which virus is this based on the Response in Animal Cell.

  • Cells round up; no inclusions.
A

Influenza virus

62
Q

Determine which virus is this based on the Response in Animal Cell.

  • No change in cell shape; cytoplasmic inclusions (Negri bodies).
A

Rabies virus

63
Q

Determine which virus is this based on the Response in Animal Cell.

  • Syncytia form (multinucleate).
A

Measles virus

64
Q

WHAT IS THIS?

  • It occurs when a host cell harbors a virus without immediate destruction. These infections can last for weeks, months, or even a lifetime.
A

Persistent Infection

ADD: The virus remains in the host cell without causing immediate lysis.

65
Q

WHAT IS THIS?

  • This is when some viruses reactivate periodically, causing symptoms to return.
A

Chronic latent state

66
Q

What example of Persistent Virus is this?

  • Can remain hidden in brain cells for years.
A

Measles Virus

67
Q

What example of Persistent Virus is this?

  • Causes cold sores and genital herpes.
A

Herpes Simplex Virus

68
Q

What example of Persistent Virus is this?

  • Causes chickenpox in initial infection.
  • Reactivates later in life as shingles (painful rash along nerve pathways)
A

Herpes zoster virus

69
Q

WHAT IS THIS?

  • Some animal viruses enter the host cell and permanently alter its genetic material resulting in cancer. This is called as what?
A

“Transformation of the cell”

Characteristics of Transformed Cells:

✔ Increased rate of growth (uncontrolled cell division).
✔ Chromosomal alterations (mutations in DNA).
✔ Indefinite cell division (loss of normal cell death, leading to tumors).

70
Q

WHAT IS THIS?

  • These are viruses that can trigger cancer by integrating their genes into the host’s DNA.
A

Oncoviruses

Note:

  • These are mammalian viruses capable of initiating tumors.
71
Q

What type of Oncoviruses (Cancer-Causing Viruses) is this?

  • Causes cervical cancer, as well as throat and anal cancers.
A

Papillomavirus

72
Q

What type of Oncoviruses (Cancer-Causing Viruses) is this?

  • Associated with Burkitt’s lymphoma (a type of aggressive B-cell cancer.
A

Epstein-Barr Virus

73
Q

WHAT IS THIS?

  • These are viruses that infect bacteria (bacterial viruses). The most widely studied are phages that infect Escherichia coli (E. coli), which have complex structures and contain DNA genomes.
A

Bacteriophages

“Key Differences Between Bacteriophage & Animal Virus Multiplication:”

✔ Only the nucleic acid enters the bacterial cytoplasm (no need for uncoating).

✔ Lysis is the primary method of release, as phages break the bacterial cell open.

74
Q

WHAT IS THIS?

  • This is a process where the virus infects, replicates, and destroys the bacterial host.
  • Release is a result of cell lysis induced by viral enzymes and accumulation of viruses.
A

Lytic cycle

75
Q

Bacteriophages replicate inside bacteria through the lytic cycle, which results in the destruction of the host cell.

What are the (6) Steps in Phage Replication?

A
  • Adsorption
  • Penetration
  • Replication
  • Assembly
  • Maturation
  • Lysis & Release

Remember the acronym AP-RAM-L

76
Q

Under the Steps in Phage Replication

  • Binding of virus to specific molecules on host cell.
A

Adsorption

77
Q

Under the Steps in Phage Replication

  • Genome enters host cell.
A

Penetration

78
Q

Under the Steps in Phage Replication

  • Viral components are produced.
A

Replication

79
Q

Under the Steps in Phage Replication

  • Viral components are assembled.
80
Q

Under the Steps in Phage Replication

  • Completion of viral formation.
A

Maturation

81
Q

Under the Steps in Phage Replication

  • Virus leave the cell to infect other cells.
A

Lysis & Release

82
Q

Comparison of the two in _________.

  • Bacteriophage: Precise attachment of special tail fibers to cell wall.
  • Animal Virus: Attachment of capsid or envelope to cell surface receptors.
A

Adsorption

83
Q

Comparison of the two in _________.

  • Bacteriophage: Injection of nucleic acid through cell wall; no uncoating of nucleic acid
  • Animal Virus: Whole virus is engulfed and uncoated, or virus surface fuses with cell membrane; nucleic acid is released.
A

Penetration

84
Q

Comparison of the two in _________.

Bacteriophage:

  • Occurs in cytoplasm
  • Cessation of host synthesis
  • Viral DNA or RNA replicated
  • Viral components synthesized

Animal Virus:

  • Occurs in cytoplasm and nucleus
  • Cessation of host synthesis
  • Viral DNA or RNA replicated
  • Viral components synthesized
A

Synthesis and Assembly

85
Q

Comparison of the two in _________.

  • Bacteriophage: Lysogeny
  • Animal Virus: Latency, chronic infection, cancer
A

Viral Persistence

86
Q

Comparison of the two in _________.

  • Bacteriophage: Cell lyses when viral enzymes weaken it.
  • Animal Virus: Some cell lyse; enveloped viruses bud off host cell membrane.
A

Release from Host Cell

87
Q

Comparison of the two in _________.

  • Bacteriophage: Immediate
  • Animal Virus: Immediate or delayed
A

Cell Destruction

88
Q

Which of the following is a step found in animal virus
multiplication but not in bacteriophage replication?

A. Adsorption
B. Penetration
C. Uncoating
D. Assembly
E. Release

A

C. Uncoating

89
Q

This is also called as the Silent Virus Infection. What is this?

90
Q

FAMILIARIZE ONLY!

“Lysogeny: The Silent Virus Infection - Explanation of Each Point”

A

Not all phages complete the lytic cycle

*Some viruses do not immediately destroy the host cell. Instead of replicating and lysing the bacterial cell right away (as in the lytic cycle), they enter a dormant phase.

Some DNA phages, called temperate phages, undergo adsorption and penetration but don’t replicate

  • Temperate phages attach (adsorption) and inject their genetic material (penetration) into the bacterial cell. However, instead of immediately taking over the host machinery to replicate, they stay inactive.

The viral genome inserts into the bacterial genome and becomes an inactive prophage – the cell is not lysed

  • The viral DNA integrates into the bacterial chromosome and becomes part of its genetic material. In this inactive state, the virus is called a prophage. Since the virus does not produce new viral particles, the bacterial cell remains alive.

Prophage is retained and copied during normal cell division, resulting in the transfer of temperate phage genome to all host cell progeny – lysogeny

  • Each time the bacterium divides, it copies its DNA—including the prophage—to its daughter cells. This means all new bacterial cells inherit the viral DNA, making the infection spread silently without destroying the host cells.

Induction can occur, resulting in activation of lysogenic prophage followed by viral replication and cell lysis

  • Under certain conditions (e.g., UV light, chemicals, stress), the prophage “wakes up” and enters the lytic cycle. The virus then begins replicating, assembling new phages, and eventually bursts (lyses) the bacterial cell, releasing many new viruses.

Why is Lysogeny Important, and How Does It Affect Disease Spread?

✔ Hidden Infection: Since lysogeny does not kill the host right away, viruses can remain undetected for long periods, increasing survival chances.

✔ Silent Spreading: The viral genome spreads every time the bacterium divides, meaning hundreds or thousands of bacterial cells may carry the viral DNA without showing immediate effects.

✔ Increased Virulence (Toxin Production): Some bacterial infections only become dangerous when lysogenized by a phage carrying toxin genes.

91
Q

WHAT IS THIS?

  • Some DNA phages, called _________, undergo adsorption and penetration but don’t replicate.
A

temperate phages

92
Q

WHAT IS THIS?

  • The viral genome inserts into bacterial Genome and becomes an inactive __________ — the cell is not lysed.
93
Q

WHAT IS THIS?

  • Prophage is retained and copied during normal cell division resulting in the transfer of temperate phages genome to all host cell progeny — _________.
94
Q

WHAT IS THIS?

  • _______ can occur resulting in activation of lysogenic prophage followed by viral replication and cell lysis.
95
Q

WHAT IS THIS?

  • ________ results in the spread of the virus without killing the host cell.
A

Lysogeny

Note:

  • Unlike the lytic cycle, where viruses immediately replicate and destroy the host, lysogeny allows the virus to remain hidden inside the bacterial genome.
  • Since the virus is copied along with bacterial DNA during cell division, it can spread silently without harming the host cells right away.
96
Q

WHAT IS THIS?

  • Some temperate phages carry extra genes that change the behavior of the bacteria they infect.
  • What is the process where it can make harmless bacteria dangerous by making them produce toxins or enzymes that cause disease.
A

Lysogenic conversion

97
Q

FAMILIARIZE ONLY!

“Examples of Lysogenic Conversion in Pathogenic Bacteria”

A
  • Corynebacterium diphtheriae → Produces the diphtheria toxin, causing diphtheria (severe throat infection that can block airways).
  • Vibrio cholerae → Produces the cholera toxin, leading to severe diarrhea and dehydration (cholera).
  • Clostridium botulinum → Produces botulinum toxin, which causes botulism (paralysis and respiratory failure).
98
Q

Viruses are obligate intracellular parasites, meaning they cannot replicate on their own. They must infect a living host cell to reproduce. Because of this, growing viruses in a laboratory setting requires _____________.

What is this?

A

Living cells

99
Q

What are the (3) Techniques in Cultivating and Identifying Animal Viruses?

A
  • Cell (Tissue) Cultures
  • Bird Embryos (Embryonated Eggs)
  • Live Animal Inoculation
100
Q

WHAT IS THIS?

  • The most common and efficient method for growing viruses.
  • Cells are grown in monolayers (sheets of cells) in petri dishes or flasks.
  • Viruses infect the cells, leading to observable effects (Cytophathic Effects, CPE).
  • Used for Studying viral replication, drug testing, and vaccine production.
A

Cell (Tissue) Cultures

✅ Advantages:
✔ Allows easy observation of viral effects.
✔ Less expensive than live animals.
✔ Can be scaled up for vaccine production.

⚠ Disadvantages:
❌ Some viruses do not grow well in artificial cultures.
❌ Requires strict sterile conditions.

101
Q

WHAT IS THIS?

  • The egg is incubated, allowing the virus to multiply.
  • The virus is injected into the shell and into specific parts of the egg (amniotic sac, yolk sac, etc).
  • Used for vaccine production (like influenza vaccine)
A

Bird Embryos (Embryonated Eggs)

102
Q

WHAT IS THIS?

  • Used when cell culture or eggs are not suitable.
  • Animals (mice, rabbits, monkeys, etc.) are infected with the virus.
  • Observations are made for disease symptoms, immune responses, and viral effects.
A

Live Animal Inoculation

✅ Advantages:
✔ Useful for studying host-virus interactions.
✔ Necessary for studying viruses that do not grow in culture.

⚠ Disadvantages:
❌ Ethical concerns 😔
❌ Expensive and time-consuming.

103
Q

FAMILIARIZE ONLY!

“Medical Importance of Viruses”

A

1. Viruses are the most common cause of acute infections

Acute infections happen suddenly and last for a short time.

Examples:

  • Influenza (flu)
  • Common cold (rhinovirus, coronavirus)
  • Gastroenteritis (norovirus, rotavirus)

2. Several billion viral infections per year

3. Some viruses have high mortality rates

Some viruses cause severe disease and death, even though they are microscopic.

Examples of deadly viruses:

  • Rabies (almost 100% fatal if untreated)
  • Ebola (up to 90% fatality rate)
  • HIV/AIDS (destroys the immune system)

4. Possible connection of viruses to chronic afflictions of unknown cause

Some chronic (long-term) diseases may be caused by viruses, even if the link is not fully understood.

104
Q

WHAT IS THIS?

  • These are misfolded proteins that cause disease.
  • Unlike viruses, they contain no DNA or RNA – only protein.
  • They induce normal proteins to misfold, leading to severe brain damage.
A

PRIONS

Why Are Prions Dangerous?
✅ Extremely resistant to heat, radiation, and chemicals.
✅ Cannot be destroyed by usual sterilization methods (e.g., autoclaving).
✅ Cause slow but fatal neurodegenerative diseases.

105
Q

Prion diseases are known as ___________ because they create sponge-like holes in the brain.

A

Transmissible Spongiform Encephalopathies (TSEs)

106
Q

What are the (3) Common Prion Diseases in Animals?

A
  • Scrapie
  • Bovine Spongiform Encephalopathy (BSE)
  • Chronic Wasting Disease (CWD)
107
Q

What Prion Disease is this?

  • Affects sheep and goats; causes itching, loss of coordination, and death.
108
Q

What Prion Disease is this?

  • Also called as Mad Cow Disease; leads to erratic behavior and motor dysfunction in cattle.
A

Bovine Spongiform Encephalopathy (BSE)

109
Q

What Prion Disease is this?

  • Found in elk and deer; results in weight loss, lethargy, and neurological symptoms.
A

Chronic Wasting Disease (CWD)

110
Q

This is an Example of Prion Disease in Humans where it causes memory loss, personality changes, muscle twitching, and eventual death.

A

Creutzfeldt-Jakob Disease (CJD)

111
Q

Aside from viruses and prions, there are other infectious agents that can cause diseases despite lacking a full viral structure.

There are 2. What are these?

A

Satellite viruses and viroids

112
Q

WHAT IS THIS?

  • These are incomplete viruses that depend on other viruses for replication. They cannot reproduce on their own.
A

Satellite viruses

113
Q

Satellite viruses have 2 examples. What are these?

A
  • Adeno-associated Virus (AAV)
  • Delta Agent (Hepatitis D Virus, HDV)
114
Q

WHAT IS THIS?

  • Can only replicate if the adenovirus is present. However, it does not cause disease and is being explored for gene therapy.
A

Adeno-associated Virus (AAV)

115
Q

WHAT IS THIS?

  • A small, naked RNA virus that only becomes infectious in the presence of Hepatitis B Virus (HBV). It worsens liver disease when co-infection occurs.
A

Delta Agent (Hepatitis D Virus, HDV)

116
Q

WHAT IS THIS?

  • These are short strands of RNA with no protein coat. They are smaller than viruses and only infect plants.
117
Q

Exposure to Nucleases that degrade DNA and RNA would damage all of the following EXCEPT

A. Animal Viruses
B. Bacteriophage
C. Prions
D. Satellite Viruses
E. Viroids

A

C. Prions

Explanation:

  • Prions are misfolded proteins that do not contain nucleic acids (DNA or RNA). Since nucleases specifically degrade DNA and RNA, prions would remain unaffected.

Microbiology and Parasitology (5 decks)

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