Lec 11 - Acute viral infections

Question 1

Compare public health importance and medical importance

Answer 1

Public health: something causing disease on large scale
Medical: something causing disease and range of clinical manifestations arising

Question 2

Define acute/primary infection

Answer 2

An infection by entry of viral genomes into cells with replication not controlled by innate immunity resulting in apparent signs

Question 3

Describe the course of a typical acute viral infection

Answer 3

1. Virus entry with sufficient innate response
2. Infection from bypassing innate response
3. Adaptive immunity clears infection and induces memory

Question 4

Why are acute viral infections hard to control in public health?

Answer 4

Asymptomatic transmission resulting in ineffective control and antiviral therapy

Question 5

What Baltimore group is MV in and what are the main features and transmission method?

Answer 5

• Group 5 with (-) ssRNA genome
• Most contagious (1 = 20)
• Transmissitedby respiratory aerosols

Question 6

What are the symptoms and complications of MV?

Answer 6

Symptoms: maculopapular erythematous rash and Koplik spots
Complications: subacute sclerosing panencephalitis (SSPE), death etc

Question 7

What cells does MV infect and how are they affected?

Answer 7

• Memory B and T cells and alveolar macrophages
• Memory destroyed by clearance so immunocompromised
• Suppressed lymphocyte proliferation

Question 8

How does MV evade immunity in SSPE?

Answer 8

• Microfusion of neuron membranes by F protein binding neurokinin-1 receptors
• Incomplete assembly prevents budding

Question 9

What Baltimore group is SARS-CoV-2 in and how does it enter cells? What is its infectious number?

Answer 9

• Group 4 with (+) ssRNA genome
• ACE2 receptors then cleaved by TMPRSS2 to enter
• 1 = 4.9 but varies

Question 10

What cells does SARS-CoV-2 infect and who is affected the most?

Answer 10

• Pneumocytes in lungs then disseminates via blood
• Older people over 50 most severely affected

Question 11

What is the difference between a mild and severe SARS-CoV-2 infection?

Answer 11

Mild: controlled by host immunity
Severe: exaggerated immune response damaging organs

Question 12

What Baltimore group is RSV in, how is it transmitted and who is affected the most?

Answer 12

• Group 5 with (-) ssRNA genome
• Close contact or respiratory aerosols
• Almost all children by 2yo

Question 13

What cells does RSV infect and what is the result of infection? What CPE is seen?

Answer 13

• Superficial cells of upper respiratory tract then lower respiratory tract
• Changed proteins and immune response + no apoptosis = airway remodelling
• Syncytia and inclusion bodies

Question 14

What causes a severe RSV infection and what is the result?

Answer 14

Exaggerated immune response creating cytokine storm

Question 15

What antigenicity groups does RSV have, what antibodies do they produce and how long does protection last?

Answer 15

Antigenicity groups A and B produce neutralising antibodies with short immunity

Question 16

What Baltimore group is DENV in and how is it transmitted?

Answer 16

• Group 4 with (+) ssRNA genome
• Female Aedis agypti mosquito

Question 17

What protein is used in PCR diagnosis of DENV?

Answer 17

NSP1

Question 18

What people are more susceptible to DENV or have more severe infections?

Answer 18

• White people > black people
• Elderly with primary infection
• Younger with previous infection

Question 19

Describe the urban cycle of DENV transmission

Answer 19

1. Mozzie infected by feeding on infected
2. Extrinsic: virus replicates in mozzie midgut then salivary glands
3. Mozzie transmits virus by feeding
4. Intrinsic: virus replicates in human

Question 20

What is the main concern with previous DENV infection?

Answer 20

Memory from 1 serotype enhances infection by another serotype due to genetic differences between serotypes