Lecture 36. Consequence of Infection

Question 1

What are the modes of virus transmission ?

Answer 1

1. Direct contact
2. Aerosols and droplets
3. Contaminated surfaces
4. Vector - mosquito
5. Mother to child
6. Bodily fluids

Question 2

How do viruses enter the body ?

Answer 2

1. Skin
2. Mucosal surfaces - respiratory, enteric, genital tract
3. Eyes
4. Blood
5. Bites

Question 3

What are the common infection patterns of acute infections ?

Answer 3

1. Rapid onset of disease

2. Rapid production of virions, followed by clearance and elimination of infection by host

Question 4

What are some examples of acute infections ?

Answer 4

1. Poliovirus
2. Influenza
3. Norovirus
4. Zika virus

Question 5

What are the common patterns of infection of persistent infections ?

Answer 5

1. Smouldering infections - low levels replication for many years
2. Infection not cleared by host
3. Virions produces continuously or intermittently

Question 6

What are some examples of persistent infection ?

Answer 6

1. HIV

2. Varicella zoster virus

Question 7

What are the two types of persistent viral infections ?

Answer 7

1. Chronic infection

2. Latent infection

Question 8

What is a chronic persistent infection and give an example ?

Answer 8

Has a low level replication of viruses in tissues which regenerate.

Papillomavirus and cervical virus

Question 9

What is a persistent latent infection and give examples?

Answer 9

Viral genomes are maintained but virions are not formed until episodes of reactivation

Herpes simplex in cold sores and varicella zoster virus and shingles

Question 10

What are the steps in the pyramid of disease severity ?

Answer 10

1. Asymptomatic infection
2. Mild symptoms
3. Sick
4. Very sick
5. Succumbs to virus

Question 11

What is the genome of the acute measles infection ?

Answer 11

Negative sense single stranded RNA genome

Question 12

How is acute measles transmitted ?

Answer 12

Respiratory droplets/aerosols

Question 13

What are the symptoms of acute measles ?

Answer 13

Fever, cough, respiratory infection, leucopenia

Question 14

What can persistent measles cause ?

Answer 14

Subacute sclerosing panencephalitis

Question 15

What does subacute sclerosing panencephalitis cause ?

Answer 15

Neurological impairment, loss of control of limbs, behavioural problems, impaired eyesight, mental deterioration, seizures, paralysis, death

Question 16

What is subacute sclerosing panencephalitis caused by ?

Answer 16

Persistent defective measles virus infection of the central nervous system

Question 17

What can effect the outcome of infection ?

Answer 17

1. Virus load
2. Pathogenicity and virulence
3. Virus sequence
4. Host immune response/status
5. Host co-morbidity (smokes, obese
6. Co-infections
7. Other medications
8. Host genetics
9. Host age, gender

Question 18

What is interesting about the viral load in chicken pox ?

Answer 18

The first child in a family usually has it mild, the second children has a higher dose of virus and is sicker

Question 19

What is pathogenicity ?

Answer 19

The ability of the virus to cause disease

Question 20

What is virulence ?

Answer 20

Describes the capacity of a virus to cause disease

Question 21

What are virulence determinants ?

Answer 21

1. Enhance replication
2. Modify host defense
3. Facilitate spread - receptor flexibility
4. Direct toxicity - diarrhoea, vomiting

Question 22

What may two strands of poliovirus vary in ?

Answer 22

Their virulence

Question 23

What does a single mutation in the genome separate in poliovirus ?

Answer 23

2 very different strains

Question 24

What are the two strains of poliovirus ?

Answer 24

1. Attenuated and used as a live vaccine

2. Invades the motorneurons and causes flaccid paralysis

Question 25

What cancers are viruses a major contributor of ?

Answer 25

Liver cancer and cervical cancer

Question 26

What is oncogenesis not required for ?

Answer 26

Replication of virus

Question 27

What is oncogenesis a side effect of ?

Answer 27

The host response to infection

Question 28

What do cancer associated viruses induce changes in ?

Answer 28

Cell cycle control and cell proliferation

Question 29

What is viremia ?

Answer 29

Virus in the blood

Question 30

What symptoms does minor poliovirus cause ?

Answer 30

Sore throat, fever, disease, malaise

Question 31

Where does the major poliovirus disease enter ?

Answer 31

The central nervous system

Question 32

Where does major poliovirus replicate ?

Answer 32

In motor neurons within spinal cord, brain stem or motor cortex

Question 33

What are the two types of paralytic polio ?

Answer 33

1. Spinal polio | 2. Bulbospinal polio

Question 34

What is spinal polio ?

Answer 34

Affects motor neurons responsible for movement of muscles

Question 35

What is bulbospinal polio ?

Answer 35

Affects upper part of cervical spinal cord causing paralysis of the diaphragm - iron lung

Question 36

What are some effects of acquired immune deficiency syndrome ?

Answer 36

1. Immune deficiency - opportunistic infections and opportunistic cancers 2. Wasting syndrome - Weight loss and fatigue 3. Brain- AIDS dementia

Question 37

How can you control viral infection ?

Answer 37

1. Anti-viral drugs | 2. Vaccines

Question 38

How to reduce animal to human transmission ?

Answer 38

1. Identify animal reservoir 2. Close live animal markets 3. Slaughter infected animals 4. Discourage bush meat hunting and selling

Question 39

How can you reduce human to human transmission ?

Answer 39

1. Condoms , needle exchanges 2. Alter funeral practices 3. Travel restrictions 4. Vaccination and herd immunity

Question 40

What are two concepts that apply to vaccines and antiviral drugs ?

Answer 40

1. Viruses are obligate, intracellular parasites - any intervention to host virus relationship carries inherent risks for host 2. Any agent that blocks virus replication or reduces viral pathogenesis imposes selection pressures on the virus that can lead to mutations

Question 41

How do antiviral drugs work ?

Answer 41

By blocking key steps in virus replication cycle

Question 42

What must an antiviral compound do ?

Answer 42

Completely block viral replication

Question 43

What is not acceptable for an antiviral ?

Answer 43

Partial inhibition

Question 44

Why is partial inhibition not an acceptable antiviral ?

Answer 44

Viruses mutate and develop drug resistance

Question 45

What are the covid treatments being approved ?

Answer 45

Remdesivir

Question 46

How is remdesivir delivered ?

Answer 46

Intravenous

Question 47

How does remdesivir work ?

Answer 47

Binds to viral RNA dependent RNA polymerase and inhibits viral replication via premature termination of RNA transcription

Question 48

What are the two covid treatments being approved ?

Answer 48

1. Molnupiravir | 2. Paxloid

Question 49

How does molnupiravir work ?

Answer 49

Acts as adapted ribonucleoside triphosphate when incorporated into RNA by viral RNA dependent RNA polymerase it results in the accumulation of errors in the viral genome, producing non-infectious virus particles

Question 50

How Paxloid work ?

Answer 50

Protease inhibitor prevents the viral protease from cleaving viral polyproteins into functioning individual proteins

Question 51

What is Paxloid delivered with and why?

Answer 51

Ritonavir Slows the breakdown of the protease inhibitor

Question 52

What is the aim of a vaccine ?

Answer 52

1. Stimulate the immune system 2. Prevent infection 3. Prevent the spread of virus within a population