[W1] Viral infections

Question 1

What do all viruses require to replicate?

Answer 1

A host.

Question 2

What environmental factors inactivate most viruses?

Answer 2

Heat, desiccation, and UV light.

Question 3

Which type of viruses are more resistant to inactivation?

Answer 3

Viruses spread via the faecal-oral route.

Question 4

What are the three main stages of viral infection?

Answer 4

• Entry
• dissemination (spread from cell to cell)
• transmission (host to host spread)

Question 5

What are the types of transmission?

Answer 5

Horizontal, vector-borne, and vertical.

Question 6

Name common portals of entry for viruses.

Answer 6

Eyes, mouth, skin, urogenital tract, anus.

Question 7

Which viruses infect via the eyes?

Answer 7

Adenovirus (8, 22), Herpes simplex virus.

Question 8

Which viruses infect via skin abrasions?

Answer 8

Hepatitis B, HPV, HIV-1, HSV-2, Rubella (via placenta).

Question 9

What determines if infection remains localized or becomes systemic?

Answer 9

The primary cell interaction (tropism).

Question 10

Name three viral dissemination mechanisms.

Answer 10

Direct cell-to-cell contact, bloodstream (viraemia), nervous system.

Question 11

What is viral tropism?

Answer 11

The specificity of a virus for certain host cell types.

Question 12

What factors affect viral tropism?

Answer 12

Entry receptors, permissivity, accessibility, immunity.

Question 13

What is a cytocidal infection?

Answer 13

An infection resulting in cell death.

Question 14

What are the durations of viral infections?

Answer 14

Acute (1–2 weeks), chronic (months–years), latent (lifetime).

Question 15

What body fluids/tissues can shed viruses?

Answer 15

Respiratory secretions, saliva, blood, semen, urine, faeces, skin lesions, breast milk.

Question 16

Name common horizontal transmission media.

Answer 16

Saliva, blood, semen, urine, faeces, direct contact, animal bites.

Question 17

Why is the respiratory tract a common site for infection?

Answer 17

Large surface area, direct contact with air, presence of goblet cells.

Question 18

What protects the GI tract from viruses?

Answer 18

Acidic pH, enzymes, bile salts, IgA, mucus, and commensal bacteria.

Question 19

What makes the urogenital tract inhospitable to viruses?

Answer 19

Low pH, mucus, urine flow.

Question 20

What are common diagnostic methods?

Answer 20

Signs/symptoms, culture, microscopy, serology, molecular diagnostics.

Question 21

What is a Tzanck smear used to detect?

Answer 21

HSV-induced cell fusion (multinucleated giant cells).

Question 22

What is ELISA used for?

Answer 22

Detecting antigens or antibodies.

Question 23

What is the therapeutic index formula?

Answer 23

TI = CC50 / EC50.

Question 24

What is considered a good therapeutic index for antivirals?

Answer 24

100–1000.

Question 25

What is a major problem in antiviral drug development?

Answer 25

Selectivity and resistance.

Question 26

What are the types of vaccines?

Answer 26

Live attenuated, inactivated, subunit, VLP, nucleic acid, recombinant vector.

Question 27

What is the main risk of live attenuated vaccines?

Answer 27

Cannot be used in immunocompromised people.

Question 28

What are VLP vaccines?

Answer 28

Virus-like particles with no nucleic acid (non-infectious).

Question 29

What is passive immunisation?

Answer 29

Providing antibodies directly (e.g. Palivizumab, VZIG).

Question 30

What does HAART stand for?

Answer 30

Highly Active Antiretroviral Therapy.

Question 31

What are adjuvants used for in vaccines?

Answer 31

Enhancing the immune response.

Question 32

Why do viruses need a host?

Answer 32

Viruses lack the machinery to replicate on their own and require host cellular machinery to replicate.

Question 33

What factors easily inactivate most viruses?

Answer 33

Heat, desiccation (drying), and UV light.

Question 34

Which viruses are resistant to environmental factors?

Answer 34

Faecal-oral transmitted viruses.

Question 35

What are the three main stages of viral infection?

Answer 35

1. Entry into host 2. Dissemination within host 3. Transmission to new hosts.

Question 36

What are the three types of transmission between hosts?

Answer 36

Horizontal, vector-borne, and vertical.

Question 37

What are the portals of entry in mammals?

Answer 37

Eyes, mouth, skin, urogenital tract, anus.

Question 38

Name viruses that enter via the eye.

Answer 38

Adenovirus (types 8, 22), Herpes simplex virus.

Question 39

Which viruses enter via skin (animal bites)?

Answer 39

Japanese encephalitis virus, West Nile virus, Dengue virus, Rabies virus.

Question 40

Which viruses enter via skin abrasions or injury?

Answer 40

Hepatitis B, HPV, HIV-1, HSV-2, Rubella virus (via placenta).

Question 41

Which viruses infect through the respiratory tract?

Answer 41

Influenza, Rhinovirus, Parainfluenza, RSV, SARS, MERS, EBV, Measles, Mumps, Rubella, VZV, Adenovirus.

Question 42

Which viruses infect the GI tract?

Answer 42

Norovirus, Rotavirus, Adenovirus (40 & 41), Hepatitis A, Poliovirus.

Question 43

What is viral tropism?

Answer 43

The ability of a virus to infect specific cell types.

Question 44

What factors determine viral tropism?

Answer 44

Entry receptor presence, permissivity, accessibility, and immunity.

Question 45

What are the three dissemination mechanisms?

Answer 45

Direct cell-to-cell contact, bloodstream (viraemia), nervous system.

Question 46

What is passive vs. active viraemia?

Answer 46

Passive: direct entry into blood (e.g. transfusion); Active: virus replicates and enters blood.

Question 47

What is a cytocidal infection?

Answer 47

Infection that kills the host cell, often via lysis.

Question 48

What are the durations of viral infections?

Answer 48

Acute (1-2 weeks), Chronic (months to years), Latent (lifetime).

Question 49

What distinguishes latent infections?

Answer 49

Episodic reactivation, limited gene expression, genome persistence.

Question 50

How does the respiratory tract defend against viruses?

Answer 50

Goblet cells secrete mucin, cilia sweep mucus, secretory IgA neutralizes viruses.

Question 51

What protects alveoli from infection?

Answer 51

Alveolar macrophages (no cilia or mucus present).

Question 52

Why is the GI tract inhospitable for viruses?

Answer 52

Extreme pH, bile salts, proteases, mucus with IgA, commensal bacteria.

Question 53

What type of viruses commonly infect the GI tract?

Answer 53

Acid- and bile-stable non-enveloped viruses (e.g. Rotavirus, Norovirus).

Question 54

What protects the eyes from infection?

Answer 54

Basal tears and blinking remove particles.

Question 55

What can cause blindness via the eye?

Answer 55

HSV-1 can infect through corneal microabrasions and damage retina.

Question 56

Why is the skin an effective barrier?

Answer 56

The epidermis is made of dead, non-replicative cells without vasculature.

Question 57

How do viruses infect through skin?

Answer 57

Via injury, abrasion, or bites reaching subcutaneous tissues.

Question 58

How are arboviruses transmitted?

Answer 58

Via arthropods, often after replicating in their salivary glands.

Question 59

Name human dead-end hosts for arboviruses.

Answer 59

Japanese encephalitis, West Nile virus.

Question 60

Name arboviruses where humans are reservoirs.

Answer 60

Dengue, Yellow fever, Chikungunya.

Question 61

What are modes of vertical transmission?

Answer 61

In utero (placenta), during childbirth, via breast milk.

Question 62

Examples of vertically transmitted viruses?

Answer 62

HIV, Zika, Rubella, VZV.

Question 63

What are common diagnostic methods for viruses?

Answer 63

Symptoms, virus culture, microscopy, serology, molecular tests.

Question 64

What is a Tzanck smear used for?

Answer 64

Detecting HSV syncytia in skin lesions.

Question 65

What is 'owl eye' inclusion a sign of?

Answer 65

Cytomegalovirus infection in lung tissue.

Question 66

What tests detect viral nucleic acid?

Answer 66

PCR, RT-PCR, blotting (Southern/Northern), hybridization, sequencing.

Question 67

What is VirCapSeq-VERT used for?

Answer 67

High-throughput sequencing for virus detection.

Question 68

What is the formula for Therapeutic Index (TI)?

Answer 68

TI = CC50 / EC50.

Question 69

Why is resistance common in antivirals?

Answer 69

Viruses mutate quickly, sometimes with a fitness cost.

Question 70

What are prodrugs?

Answer 70

Modified drugs that become active in the body (e.g., Valaciclovir).

Question 71

What are markers of antiviral efficacy in lab tests?

Answer 71

Reduced virus titer, biomarkers, CPE, clinical signs.

Question 72

What is TCID50?

Answer 72

Dose of virus needed to infect 50% of cultures.

Question 73

What does passive immunotherapy involve?

Answer 73

Administration of neutralizing antibodies (e.g. Zmapp, Palivizumab).

Question 74

What are immunomodulators?

Answer 74

Agents like interferons and imiquimod that boost the immune response.

Question 75

What are the types of vaccines?

Answer 75

Live attenuated, inactivated, subunit, VLP, nucleic acid-based, vector-based.

Question 76

What’s a risk of live attenuated vaccines?

Answer 76

Not safe for immunocompromised individuals.

Question 77

What are VLPs?

Answer 77

Virus-like particles with capsid proteins but no genome (non-infectious).

Question 78

What is an adjuvant?

Answer 78

A substance that enhances immune response to a vaccine.

Question 79

What is MF59?

Answer 79

An adjuvant used in flu vaccines to promote cytotoxic T-cell response.

Question 80

What is the difference between DNA and mRNA vaccines?

Answer 80

DNA vaccines must enter the nucleus; mRNA vaccines act in the cytoplasm.