CSI 1: Fresher’s Flu Flashcards
What is a ‘differential diagnosis’?
Differentiating between multiple conditions associated with the same symptoms
Key differences between flu and cold symptoms
- Rapid onset vs slow onset
- First symptom: cough vs sore throat
- Systemic vs mainly upper respiratory tract (nose & sore throat)
- Sneezing, runny nose, mild phlegmy cough - cold; fatigue, aching, fever, headaches, dry cough - flu
What virus causes COVID-19, flu, cold?
- Coronavirus
- Influenza virus
- Rhinovirus (most common), coronavirus, adenovirus
*Influenza C could cause very mild cold-like symptoms but doesn’t really count
To what does coronavirus bind to enter a cell? How does it cause symptoms?
- 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
What does ACE2 (angiotensin converting enzyme 2) do?
Clears angiotensin II from the system (by converting it into angiotensin (1-7)
Renin-Angiotensin System and Angiotensin II
- 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
What can excess angiotensin II in the system lead to?
Adverse myocardial remodelling and acute lung injury
How does influenza enter a cell?
- Haemagglutinin (a glycoprotein) on viral membrane binds to sialic acid on host cell membrane
- Virus enters cell by endocytosis
What are the three main molecules involved in influenza’s MOA?
HA, NA, Matrix-2
What is the purpose of neuraminidase?
Tis a glucoside hydrolase enzyme, which cleaves the sialic acid group that is tethering the original virus/budding virion to the host csm
How does rhinovirus enter a cell?
The multiprotein groove on the protein shell of rhinovirus binds to ICAM1 on the host cell surface membrane.
Key risk factors during fresher’s week
- Lack of sleep
- Alcohol (source of calories, replacing healthier food; acetaldehyde toxic breakdown product)
- Poor diet
- Close proximity, crowding
- Meeting new people
Key risk factors for the general population
- Age
- Comorbidities, chronic illness
- Immune disorder
- Pregnancy
- People living in long term facilities
- Obesity BMI>40
How does exercise affect your risk of getting the common cold?
- Moderate exercise - increased levels of cortisol, improving immune function; adrenaline released has a pro-immune effect too
- Intense exercise - cortisol levels too high, becoming immune suppressive
How does stress affect your risk of getting the common cold?
The higher the individual’s stress, the more cortisol is released in high levels => risk of infection increases as immune system is weakened
How does sleep affect your risk of getting the common cold?
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
How are different strains of virus differentiated between?
Subtype, geographical origin, year of isolation, species of origin
How do different subtypes of viruses differ from each other?
By their surface proteins i.e. antigenic material
What are Zola’s triggers?
- Interpersonal crisis
- Interference with personal/social relations
- Sanctioning
- Interference with vocational/physical activity
- Temporalising
What is an illness behaviour?
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
What is Helman’s Folk model of illness?
- What has happened?
- Why has it happened?
- Why to me?
- Why now?
- What would happen, if nothing is done?
- What should I do about it/who should I turn to for help?
What is unique about influenza C?
- It is structurally different to influenza A
- Causes mild upper respiratory tract illness -> common cold
What is antigenic drift?
- 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
What is antigenic shift?
- Abrupt major change in genetic material
- Confers a phenotypic change that needs an entirely new antigenic response
- Risk of pandemic
- Only in influenza A
Why can antigenic shift only happen in Influenza A?
- 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
Other than acting as way of viral entry into the cell, what can haemagglutinin do?
- Act as an attachment factor
- By binding to sialic acid on erythrocytes causing haemagglutination [a network of interconnected RBCs and viral particles]
