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NUR1142 > Module 9 2.Patho: Describes the four main classes of infectious microorganism: Parasites/Protozoans: Viruses > Flashcards

Module 9 2.Patho: Describes the four main classes of infectious microorganism: Parasites/Protozoans: Viruses Flashcards

1
Q

What is the prevalence of viral diseases among humans?

A

Viral diseases are the most common afflictions in humans, spanning from mild conditions like the common cold to severe diseases like cancer and AIDS.

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2
Q

What is the basic structure of viruses?

A

Viruses are simple microorganisms characterized by a nucleic acid core protected by one or more protein layers, known as the capsid.

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3
Q

What are the different types of viral genomes?

A

Viral genomes can be double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), double-stranded RNA (dsRNA), or single-stranded RNA (ssRNA).

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4
Q

What distinguishes certain viruses like HIV, herpesviruses, and influenza virus in terms of their interaction with host cells?

A

These viruses bud from the surface of an infected cell, retaining a portion of the cell’s plasma membrane as an envelope, which adds protection

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5
Q

What is the primary factor determining the replication of viruses?

A

Viral replication is entirely dependent on their ability to infect a permissive host cell, one that cannot resist viral invasion and replication.

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6
Q

Why are viruses considered obligatory intracellular microbes?

A

Viruses are classified as obligatory intracellular microbes because they rely on host cells for their replication.

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7
Q

How do viruses typically spread from infected individuals to uninfected individuals?

A

Virus transmission commonly occurs through means like aerosols of respiratory tract fluids, contact with infected blood, sexual contact, or transmission from an animal reservoir, often involving a vector like mosquitoes.

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8
Q

What is the Baltimore Classification, and how is it used to categorize human diseases caused by specific viruses?

A

The Baltimore Classification system categorizes viruses based on their genetic material and characteristics, and it is used to classify human diseases caused by specific viruses.

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9
Q

Provide some examples of viruses belonging to the dsDNA category, and mention whether they have envelopes.

A

Examples include adenoviruses (no envelope) and herpesviruses (with envelope).

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10
Q

How is herpes simplex virus type 1 (HSV-1) primarily transmitted, and what disease does it cause?

A

HSV-1 is transmitted through direct contact with saliva or lesions and causes lesions in the mouth, pharynx, and conjunctivitis.

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11
Q

Which virus is known to cause chickenpox and shingles?

A

The Varicella-zoster virus (VZV) is responsible for causing chickenpox and shingles.

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12
Q

What is the main transmission route for hepatitis C virus, and what diseases does it cause?

A

Hepatitis C virus is transmitted through blood or sexual contact and can result in acute or chronic hepatitis and hepatocellular carcinoma.

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13
Q

What type of virus is influenza, and how is its genome structured?

A

Influenza is an ssRNA virus with a segmented genome composed of eight pieces of single-stranded RNA.

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14
Q

How is influenza primarily transmitted, and what is its level of infectivity?

A

Influenza is primarily transmitted through aerosols or body fluids and is highly infectious. Its typical infectivity rate ranges from 5 to 15%.

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15
Q

What are some common symptoms of influenza, and how soon do they appear after infection?

A

Symptoms of influenza include chills, fever, sore throat, muscle aches, severe headaches, coughing, weakness, generalized discomfort, nausea, and vomiting. They typically appear 1 to 4 days after infection.

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16
Q

Who is at higher risk of fatal outcomes from influenza?

A

Influenza can be fatal, particularly in young children and older individuals.

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17
Q

What is the estimated mortality rate for influenza, and how long does it usually take for recovery?

A

Influenza has an average mortality rate of about 0.1%, and most cases recover within 1 to 2 weeks.

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18
Q

How many deaths do yearly seasonal influenza outbreaks result in worldwide?

A

Yearly seasonal influenza outbreaks lead to approximately 250,000 to 500,000 deaths worldwide.

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19
Q

What is the initial step in the life cycle of every virus?

A

The first step in the virus life cycle is attachment to a receptor on the target cell.

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20
Q

Which two surface proteins of the influenza virus are essential for virulence, and what are their functions?

A

Hemagglutinin (HA) is essential for cell entry by binding to glycan receptors on the respiratory tract epithelium, and neuraminidase (NA) is necessary for the release of new virions from infected cells by cleaving cellular sialic acids.

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21
Q

What does the term “tropism” refer to in the context of viruses?

A

Tropism describes the specificity of the virus-receptor interaction, determining the range of host cells a virus can infect and influencing the clinical symptoms of infection.

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22
Q

What specific receptor does the HIV virus attach to, and on which type of cells?

A

HIV attaches to CD4 on T-helper cells.

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23
Q

Which receptor does Epstein-Barr virus (EBV) attach to, and what diseases are associated with it?

A

EBV attaches to complement receptor 2 (CR2) on B lymphocytes (B cells) and is linked to mononucleosis and Burkitt lymphoma.

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24
Q

What receptor does rhinovirus attach to, and what type of cells does it infect?

A

Rhinovirus attaches to intracellular adhesion molecule-1 (ICAM-1) on respiratory tract epithelium and is responsible for causing the common cold.

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25
Q

How does the SARS-CoV-2 virus responsible for COVID-19 gain entry into the host?

A

SARS-CoV-2 enters the host by binding to the ACE-2 receptor.

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26
Q

In which parts of the body are ACE-2 receptors expressed, and what is their primary function?

A

ACE-2 receptors are expressed in the lungs, kidneys, and gastrointestinal tract and serve a protective function.

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27
Q

What role does the ACE-2 receptor play in regulating angiotensin II?

A

ACE-2 receptors break down angiotensin II, regulating its levels.

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28
Q

What happens when SARS-CoV-2 binds to the ACE-2 receptor, and how does this affect angiotensin II levels?

A

SARS-CoV-2 binding inhibits ACE-2 function, leading to increased levels of angiotensin II.

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29
Q

What are the consequences of elevated angiotensin II in the body?

A

Elevated angiotensin II can cause tissue damage, inflammation, vasoconstriction, and adverse effects.

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30
Q

How does reduced ACE-2 activity in the lungs affect the alveoli and respiratory function in COVID-19 patients?

A

Reduced ACE-2 activity in the lungs can lead to cell death in the alveoli, decreased surfactant production, inflammation, vasoconstriction, and the development of acute respiratory distress syndrome (ARDS).

31
Q

What are the main steps in the viral life cycle?

A

he viral life cycle includes attachment, penetration, uncoating, replication, assembly, and release.

32
Q

How does the influenza virus enter respiratory tract epithelial cells?

A

The influenza virus enters respiratory tract epithelial cells via endocytosis.

33
Q

What triggers the fusion between the endosome and the viral envelope during viral entry?

A

Low pH conditions lead to the fusion between the endosome and the viral envelope, causing uncoating of the viral nucleic acid.

34
Q

Where is the viral ssRNA transported, and what processes occur there during the viral life cycle?

A

The viral ssRNA is transported to the nucleus, where transcription and replication take place using viral RNA-dependent RNA polymerase.

35
Q

Where do viral proteins assemble, and what is their role in the viral life cycle?

A

Viral proteins assemble in the cytoplasm to form the matrix around the viral genome, facilitating the budding of new virions from the cell surface.

36
Q

Why do infected cells typically die, and what influences the severity of clinical symptoms during a viral infection?

A

Infected cells often die as a direct effect of the virus. The severity of clinical symptoms is often related to the level of cytokines produced by infected cells or in response to cell death.

37
Q

How do the effects of a virus on the infected cell vary?

A

The effects of a virus on the infected cell can vary greatly.

38
Q

What is the latency phase in the life cycle of some viruses, like herpesviruses?

A

The latency phase is a period during which the host cell transforms, and the viral DNA integrates into the host cell’s DNA.

39
Q

What happens during latency, and how does the virus behave in this phase?

A

During latency, the viral DNA becomes a permanent part of the cell and its progeny, remaining dormant.

40
Q

What can trigger a virus to exit latency and enter a productive cycle?

A

Stimuli like stress, hormonal changes, or disease can trigger a virus to exit latency and become active.

41
Q

How do neurons contribute to the reactivation of herpesviruses 1 and 2, and what are the consequences of this reactivation?

A

Neurons can release herpesviruses 1 and 2, leading to their infection of skin epithelium, resulting in skin lesions caused by the immune response against the infected epithelium.

42
Q

What are cytopathic effects caused by viruses?

A

Cytopathic effects are detrimental changes in infected cells caused by viruses.

43
Q

Give an example of a cytopathic effect related to DNA, RNA, and protein synthesis.

A

Cessation of DNA, RNA, and protein synthesis can occur in infected cells, as seen with herpesvirus.

44
Q

How does herpesvirus disrupt host cell lysosomes, and what is the consequence?

A

Herpesvirus can disrupt lysosomal membranes, leading to the release of lysosomal enzymes that can harm and kill the infected cell.

45
Q

What is the cytopathic effect that results in the formation of multinucleated giant cells?

A

The formation of multinucleated giant cells is a cytopathic effect observed with viruses like respiratory syncytial virus.

46
Q

How does the alteration of antigenic properties by a virus affect the infected cell?

A

It causes the individual’s immune system to attack the infected cell as if it were foreign, as seen with hepatitis B virus.

47
Q

Which virus is known to transform host cells into cancerous cells?

A

Human papillomavirus is associated with the transformation of host cells into cancerous cells.

48
Q

How can viruses promote secondary bacterial infections in damaged tissues?

A

Viruses can damage tissues, making them susceptible to secondary bacterial infections.

49
Q

What are some health issues associated with the cytopathic effects of SARS-CoV-2?

A

Cytopathic effects of SARS-CoV-2 can lead to acute respiratory distress syndrome, vascular disease, gastrointestinal irritation, and autoimmune disorders.

50
Q

How does influenza virus evade the immune system?

A

Influenza virus evades the immune system by changing viral surface antigens through antigenic variation.

51
Q

Which viral antigens are responsible for protection against influenza?

A

Antibodies against the HA and NA antigens provide protection against influenza.

52
Q

Why does previous year’s protection against influenza not fully protect in the following year?

A

The HA and NA antigens of influenza undergo yearly changes, resulting in reduced effectiveness of previous protection.

53
Q

What causes minor antigenic variation in influenza viruses (antigenic drift)?

A

Mutations in the virus contribute to minor antigenic variation.

54
Q

How does partial protection from previous infections affect the severity of influenza?

A

Partial protection from previous infections can reduce the clinical effects and severity of the disease.

55
Q

What are the two groups of influenza viruses that infect humans?

A

Influenza A and influenza B are the two groups of influenza viruses that infect humans.

56
Q

What does the yearly influenza vaccine contain, and how is it composed?

A

The yearly influenza vaccine contains inactivated proteins from two influenza A subtypes and one influenza B subtype.

57
Q

Which type of influenza virus primarily infects humans and mutates at a lower rate?

A

Influenza B primarily infects humans and has a lower mutation rate compared to influenza A.

58
Q

How many distinct forms of HA and NA antigens are found in influenza A viruses?

A

Influenza A viruses have 17 distinct forms of HA antigens and 10 distinct forms of NA antigens.

59
Q

What are the main subtypes of influenza causing infections worldwide?

A

The primary influenza subtypes causing infections worldwide are H1N1, H1N2, and H3N2.

60
Q

What are major antigenic changes in influenza A called?

A

Major antigenic changes in influenza A are known as antigenic shifts.

61
Q

Which animals can be infected by Influenza A, leading to antigenic shifts?

A

Influenza A can infect both birds and mammals, allowing antigenic shifts to occur.

62
Q

What characteristic of the influenza A genome enables the emergence of new HA or NA antigens?

A

The segmented genome of influenza A allows segments to undergo recombination, leading to new antigen emergence.

63
Q

What is characteristic of clinical influenza when no major antigenic shift occurs?

A

Without antigenic shifts, clinical influenza is typically epidemic, with the usual number of new infections.

64
Q

What is the outcome when major antigenic changes occur in influenza A?

A

Major antigenic changes lead to the loss of previous protection and can result in major pandemics, characterized by widespread severe disease.

65
Q

What has the SARS-CoV-2 virus responsible for COVID-19 undergone?

A

The SARS-CoV-2 virus has undergone antigenic drift, resulting in variants with mutations.

66
Q

How many main mutations have been observed in the SARS-CoV-2 virus?

A

Notably, there are three main mutations in the SARS-CoV-2 virus.

67
Q

What is a concerning aspect of zoonotic influenza viruses?

A

Zoonotic influenza viruses can potentially transition from animals to humans and become lethal.

68
Q

Which organizations closely monitor novel infections, including COVID-19?

A

The World Health Organization (WHO) and Public Health Agency of Canada (PHAC) closely monitor novel infections.

69
Q

As of December 31, 2020, how many global COVID-19 cases were recorded?

A

As of December 31, 2020, there were 87,247,114 global COVID-19 cases.

70
Q

What are some zoonotic influenza outbreaks currently monitored by the PHAC?

A

The PHAC monitors outbreaks involving swine influenza virus (H1N1), pathogenic H5N1 avian influenza, and a new avian influenza strain (H7N9).

71
Q

How do some viral pathogens evade defense mechanisms?

A

They hide within cells and avoid normal immune responses.

72
Q

Which viruses spread through the bloodstream and are sensitive to neutralizing antibodies?

A

Viruses like influenza and rubella spread through the bloodstream and are sensitive to neutralizing antibodies.

73
Q

Why are some viruses like measles and herpes inaccessible to antibodies after the initial infection?

A

Measles and herpes viruses remain inside infected cells, making them inaccessible to antibodies post-infection.

74
Q

What additional defense mechanisms have many viruses developed?

A

Many viruses have developed additional defense mechanisms, such as the influenza virus’s NS1 protein, which blocks the antiviral effects of type I interferon.

NUR1142 (112 decks)

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