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Medicine 2 - 03 Pneumonia > 7 Respiratory Tract Infections: Viral infections > Flashcards

7 Respiratory Tract Infections: Viral infections Flashcards

(34 cards)

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1
Q

Describe upper respiratory tract infections (URTIs)

And also state what the names are of infections of different parts of the upper respiratory tract

A
  • Anything above the trachea
  • Common (like Cold), often mild (can vary)
  • Often viral in aetiology (cause)
  • Damage from viral infection - can lead to further bacterial/fungal infections
  • Not many treatments - the key is prevention
Nose = rhinits
Throat = pharyngitis
Sinus = sinusitis
Ear = otitis media, otitis externa
Epiglottis = epiglottitis
Larynnx = laryngitis
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2
Q

Describe what coryza is

Also, list some causes of it

A

It is also known as the common cold
- It is an acute inflammatory contagious disease in the upper respiratory tract
- It is not clear which virus, but can be:
> Rhinovirus (most common)
> Parainfluenza viruses 1-4
> Coronaviruses (often asymptomatic - young people)
> Adenovirus (50 or so serotypes - the cause of conjunctivitis)
> Enterovirus

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3
Q

What can coryza (common cold) predispose some people to

A
  • Sinutitis
  • Otitis
  • Bronchitis
  • Pneumonia
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4
Q

Describe pharyngitis/tonsilitis

A

Both are very common,

  • but pharyngitis is an infection of the throat
  • and tonsilitis is an infection of tonsils

Causes:

  • Viral: adenovirus, influenza
  • Bacterial: group A streptococcus bacteria
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5
Q

Give some symptoms of pharyngitis/tonsillitis

A
  • Sore throat
  • Difficulty swallowing
  • Fever
  • White pus-filled spots on tonsils
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6
Q

Describe infectious mononucleosis

A

It is also known as glandular fever
- It is an infection of the throat

Diagnosis
- syndromic (not clear); a constellation of signs and symptoms (not autological)

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7
Q

Describe some symptoms and signs of infectious mononucleosis (aka glandular fever)

A

Symptoms:

  • Pharyngitis
  • Lymphadenopathy (cervical generalized)
  • Fever
  • Malaise

Signs:

  • atypical mononuclear cells in peripheral blood (on blood film/smear)
  • CD8 positive T cells - activate + responding to infections
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8
Q

State some causes of infectious mononucleosis (aka glandular fever)

A
  • Epstein-Barr virus (most common)
  • Cytomegalovirus (same family as EBV)
  • Toxoplasmosis (illness that can have other symptoms with muscle pain, fever, tiredness - dangerous in pregnant women as it can affect the foetus)
  • HIV seroconversion (body starts producing detectable HIV antibodies - can occur 4-6 weeks after HIV infection - similar symptoms to glandular fever)
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9
Q

Describe croup

A

It is a childhood condition that affects the trachea, bronchi, and larynx
- occurs in children, during late autumn and early winter months

Viral causes:
- Parainfluenza virus + respiratory syncytial virus

Symptoms:
- Inflammation in throat + epiglottis - gives characteristic ‘barking’ cough (like a seal)
> Inspiratory stridor due to narrowed airways (harsh)

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10
Q

Describe epiglottitis

A

It is inflammation of the epiglottis

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11
Q

Give symptoms of epiglottitis

A
  • In young children: breathing difficulties, stridor + hoarse voice
  • In adults and older children: epiglottis inflamed, swallowing difficulties, and drooling
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12
Q

Give some causes of epiglottitis

A
  • Usually caused by an infection with Haemophilus influenzae type B (HiB) bacteria - now very rare (we vaccinate against this - HiB vaccine)
  • Potentially life-threatening - can cause epiglottitis (fatal if it blocks the airway), meningitis, and septicemia
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13
Q

Give common viral causes of lower respiratory tract infections (LRTI)

A
  • Influenza viruses

- Respiratory syncytial viruses (RSV)

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14
Q

Give some rarer viral causes of lower respiratory tract infections (LRTI)

A
  • Varicella-zoster virus - chicken pocks (in children - itchy, adults - chickenpox, pneumonia - life-threatening)
  • Measles virus (giant cell pneumonia) - rare due to MMR vaccine (complications in px who are immunocompromised - leukaemia - can be fatal)
  • Cytomegalovirus (immunocompromised - virus can be latent)

MERS (and SARS) coronaviruses

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15
Q

Describe the influenza virus

and its basic genomic makeup

A 
Lots of different versions
- Genome of the virus is segmented
 > -ve ssRNA genome
- 8 segments - encode 11 proteins
- Segments 4 + 6 encode for major surface protein

> segment 4 = Haemagglutinin (HA)
segment 6 = Neuraminidase (NA)

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16
Q

Explain the typing system of influnza viruses (A, B, C)

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A

Typing is categorized on basis of internal proteins (nucleoproteins + matrix protein)

17
Q

Explain the subtyping system of influenza viruses

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A

Only applies to type A
- Defined on basis of surface protein =
> Haemagglutinin and Neuraminidase
- Subtypes numbered (like H1N1 - HA + NA)

So, every time there is an outbreak, it is based on its characteristics

e.g. A/Panama/01/1 (H1N1)
Type/where it was isolated/when it was isolated (year)/unique number for no. of samples

If type A, the subtype is named (H1N1)

18
Q

Describe influenza - the illness

Study These Flashcards
A 
'Flu-like illness' 
2 major components to illness:
- Respiratory tract symptoms
 > rhinitis, cough, shortness of breath
- Systemic symptoms:
 > fever, headache, myalgia (tiredness)

Difference between common cold + influenza
- (no systemic symptoms in the common cold)

19
Q

Describe the pathogenesis of influenza

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A
  • Pneumotropic virus i.e. infects cells
    (haemagglutinin surface protein) lining respiratory tract - down to alveoli
  • This infection is lytic (kills cells) - stripping off the respiratory epithelium

The lytic nature of the virus makes the LRT susceptible to inhalation of bacteria
- It removed 2 innate defence mechanisms
> mucus-secreting cells and cilia
- Virus triggers Interferon production - circulates in the blood (not the virus that causes the LRT symptoms)

This contributes to the feeling of illness = systemic symptoms

20
Q

List the complications of influenza

Study These Flashcards
A

Pneumonia:

  • Primary viral pneumonia
  • Secondary bacterial pneumonia
21
Q

Describe the primary viral pneumonia that arises due to influenza

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A

Primary viral pneumonia

  • Alveolar walls filled with mononuclear cells infiltrate (inflammatory responses)
  • Air spaces filled with fibrinous exudate composed of fibrinogen and fibrin
22
Q

Describe the secondary bacterial pneumonia that arises due to influenza

Study These Flashcards
A

Secondary bacterial pneumonia

  • More common
  • Air spaces filled with polymorphonuclear leukocytes (inflammatory response to bacterial infections)
23
Q

Describe the cardiovascular complications associated with influenza

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A
  • Px with underlying cardiovascular complications most at risk
  • Pathogenesis unclear -
    > could be due to myocarditis - direct spread of the virus into the myocardium
    > could be due to inflammation of lung putting extra strain on right side of heart
    (inflammation of cardiac muscle)
24
Q

Describe nervous complications associated with influenza

Study These Flashcards
A
  • Post-infectious Encephalitis (abhorrent immune response - immune system attacks brain)
  • Rare but serious complications - inflammation of the brain
25
List the high-risk patients with influenza (at-risk groups)
Influenza epidemics lead to excess deaths and hospitalizations ``` Risk groups identified: - Patients with pre-existing: > Lung disease, cardiac disease, endocrine disease, immunodeficiency, liver disease - Anyone > 65 years old - Pregnant women (complications) - Children ```
26
Describe the epidemiology of influenza
Annual winter epidemics are associated with excess deaths, hospitalizations, and other serious consequences (mainly in at-risk groups and the elderly) - Unusual, other outbreaks do not occur annually, as after 1-year - there is immunity - Whereas with influenza, this is not the case (12-month cycle) Worldwide pandemics - high mortality
27
Describe how influenza may be able to come back every 1 year - and have worldwide pandemics
Antigenic drift + antigenic shift - Gradual change in the surface proteins (HA and NA) - these small changes over time leads to antigenic drift - Antigenic shift - more dramatic - > recombination between different strains (2 different strains entering same organism in same cell at same time, exchanging genetic material as they replication) - > leads to major changes in surface proteins (HA and NA) - >leads to a different strain virus Lack of immunity - new strain leads to an outbreak Large increases in cases + hospitalizations and deaths across the world
28
Explain the concept of antigenic drift (in context to annual influenza epidemics)
Antigenic drift - Occurs in both influenza A + B viruses - (error in replication) - Random spontaneous mutation in viral genes encoding HA + NA - - leads to 1-2% amino acid sequence change But there is a Darwinian selection - whichever stain is more infectious and successful, that one thrives more - passes on its genome These changes occur in segments 4 + 6, which affect the surface proteins HA + NA - More effective if they evade vaccine + immune system - more survivability
29
Describe the changes that occur to haemagglutinin and neuraminidase, and link this to how antigenic drift can lead to annual inlfeunza epidemics
On haemagglutinin (What normally happends with vaccines/immunity): - Antibodies normally bind to different epitopes (ABCDE) on HA - These Ab will neutralise virus, but stopping the HA from binding to receptors on target cell (Ab neutralisation) So: - In these epitopes are where there the mutations are concentration in HA + NA - So true Darwinian evolution selected by host immune response, So, Ab will not affect as well/not at all as previous year's infection This accounts for inter-pandemic epidemics (recurrence of infection) - explain annual occurence of influenzas
30
Explain the concept of Antigenic shift, with relation to Influenza pandemics
Consider scenario: - There are 8 blue segments of RNA - human influenza virus - There are 9 purple segments of RNA - avian influenza virus If they mix at the same time - a new subtype is able to infect humans - Different mix of strains - new subtype able to infect humans(if changed (purple) strain infects human, the HA and NA surface proteins will be very different - the person has no immunity) Also, this person is very adapted to replicate inside a human (Very dangerous - can occur naturally)
31
Describe how influenza A reservoirs are formed, and how this leads to new subtypes of the virus are produced (and relate this back to antigenic shift)
- Wild aquatic shorebirds are the largest + most important reservoir for influenza A - Humans and other animals (wild animals, domestic + farmed poultry, pigs, horses cats, seals, mink, whales) can also get affected - Pigs support the growth of both human and avian influenza viruses ('mixing vessels') > Pig have both forms of sialic acid (which is what human and avian influenza bind to) in their respiratory tract, and so susceptible to both strains - so exchange of genetic materials can occur - new stain Leading to influenza pandemics Antigenic shift occurs only in influenza viruses - Genetic reassortment between human and non-human leads to new subtypes - Leading to 20% new amino acid differences - Emergence of a new pandemic strain > population has no existing immunity
32
Give some key measures to combat influenza pandemics
- Infection control - prevent spread (PPE, hand washing, distancing from risk category) - Medical treatment - e.g. antiviral drugs, antibiotics - Vaccinations (most vulnerable, most likely to spread it) - if the population is more immune - herd immunity + less likely to be transmitted and reducing the chance of mutation + adaptation
33
Describe the Respiratory Syncytial Virus (RSV)
It is an enveloped paramyxovirus, -ve ssRNA - Encodes for 9 polypeptides > including 2 surface proteins: Fusion (F) and Glycoprotein (G) - Highly seasonal infection (winter months) - Extremely common: most children are infected with RSV by 2 years old
34
Describe the disease that RSV can cause:
- Causes LRTI in infants: > Bronchitis, pneumonia - High hospitalization rates - Low mortality (<0.5%) Requires rapid diagnosis and appropriate infection control measures to prevent the spread - Can spread in hospital - isolation, RSV wards to prevent deaths in young infants Undergoes antigenic drift - So, reinfection occurs throughout life - Presents as URTI in older children and adults (cough/sore throat) - Increase in mortality rates in older people

Medicine 2 - 03 Pneumonia (8 decks)

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