CSI 1: Fresher’s Flu

Question 1

What is a ‘differential diagnosis’?

Answer 1

Differentiating between multiple conditions associated with the same symptoms

Question 2

Key differences between flu and cold symptoms

Answer 2

1. Rapid onset vs slow onset
2. First symptom: cough vs sore throat
3. Systemic vs mainly upper respiratory tract (nose & sore throat)
4. Sneezing, runny nose, mild phlegmy cough - cold; fatigue, aching, fever, headaches, dry cough - flu

Question 3

What virus causes COVID-19, flu, cold?

Answer 3

1. Coronavirus
2. Influenza virus
3. Rhinovirus (most common), coronavirus, adenovirus
   *Influenza C could cause very mild cold-like symptoms but doesn’t really count

Question 4

To what does coronavirus bind to enter a cell? How does it cause symptoms?

Answer 4

• Spike protein of SARS-CoV-2 binds to ACE2
• When bound, ACE2 is downregulated, more angiotensin II is produced without getting cleared away -> acute lung injury and myocardial remodelling

Question 5

What does ACE2 (angiotensin converting enzyme 2) do?

Answer 5

Clears angiotensin II from the system (by converting it into angiotensin (1-7)

Question 6

Renin-Angiotensin System and Angiotensin II

Answer 6

• RAS maintains blood pressure levels in blood cells and generates important hormones in the process
• Local/systemic infection or sepsis leads to production of angiotensin I
• Angiotensin I is converted to angiotensin II by ACE
• Angiotensin II induces vasoconstriction and moderates vascular permeability by binding to angiotensin II type 1 receptor

Question 7

What can excess angiotensin II in the system lead to?

Answer 7

Adverse myocardial remodelling and acute lung injury

Question 8

How does influenza enter a cell?

Answer 8

1. Haemagglutinin (a glycoprotein) on viral membrane binds to sialic acid on host cell membrane
2. Virus enters cell by endocytosis

Question 9

What are the three main molecules involved in influenza’s MOA?

Answer 9

HA, NA, Matrix-2

Question 10

What is the purpose of neuraminidase?

Answer 10

Tis a glucoside hydrolase enzyme, which cleaves the sialic acid group that is tethering the original virus/budding virion to the host csm

Question 11

How does rhinovirus enter a cell?

Answer 11

The multiprotein groove on the protein shell of rhinovirus binds to ICAM1 on the host cell surface membrane.

Question 12

Key risk factors during fresher’s week

Answer 12

• Lack of sleep
• Alcohol (source of calories, replacing healthier food; acetaldehyde toxic breakdown product)
• Poor diet
• Close proximity, crowding
• Meeting new people

Question 13

Key risk factors for the general population

Answer 13

• Age
• Comorbidities, chronic illness
• Immune disorder
• Pregnancy
• People living in long term facilities
• Obesity BMI>40

Question 14

How does exercise affect your risk of getting the common cold?

Answer 14

1. Moderate exercise - increased levels of cortisol, improving immune function; adrenaline released has a pro-immune effect too
2. Intense exercise - cortisol levels too high, becoming immune suppressive

Question 15

How does stress affect your risk of getting the common cold?

Answer 15

The higher the individual’s stress, the more cortisol is released in high levels => risk of infection increases as immune system is weakened

Question 16

How does sleep affect your risk of getting the common cold?

Answer 16

During sleep, WBCs migrate to lymphoid tissues, increasing chances of encountering viruses => the more sleep you get, the more time is allowed for the immune system to carry out its function

*Below five hours and risk of infection increases more steeply

Question 17

How are different strains of virus differentiated between?

Answer 17

Subtype, geographical origin, year of isolation, species of origin

Question 18

How do different subtypes of viruses differ from each other?

Answer 18

By their surface proteins i.e. antigenic material

Question 19

What are Zola’s triggers?

Answer 19

1. Interpersonal crisis
2. Interference with personal/social relations
3. Sanctioning
4. Interference with vocational/physical activity
5. Temporalising

Question 20

What is an illness behaviour?

Answer 20

The way a certain individual will respond to and monitor bodily indications that they are ill (symptoms) and decide whether or not to see a doctor

Question 21

What is Helman’s Folk model of illness?

Answer 21

1. What has happened?
2. Why has it happened?
3. Why to me?
4. Why now?
5. What would happen, if nothing is done?
6. What should I do about it/who should I turn to for help?

Question 22

What is unique about influenza C?

Answer 22

• It is structurally different to influenza A
• Causes mild upper respiratory tract illness -> common cold

Question 23

What is antigenic drift?

Answer 23

• Natural genetic mutations of a known strain that accumulate over time
• Resulting different antigenic material that might not be recognised by an immune system
• Could lead to gradual loss of immunity or vaccine mismatch

Question 24

What is antigenic shift?

Answer 24

• Abrupt major change in genetic material
• Confers a phenotypic change that needs an entirely new antigenic response
• Risk of pandemic
• Only in influenza A

Question 25

Why can antigenic shift only happen in Influenza A?

Answer 25

• Influenza A can infect other organisms, not just humans
• Human cells can only be infected by viruses with certain HAs, even though there are many avian strains
• Pigs can be infected by both human and avian strains of influenza A
• They act as a reservoir of genetic reassortment between HA/NA molecules

Question 26

Other than acting as way of viral entry into the cell, what can haemagglutinin do?

Answer 26

• Act as an attachment factor
• By binding to sialic acid on erythrocytes causing haemagglutination [a network of interconnected RBCs and viral particles]