Respiratory pathogens Flashcards
What are the types of resp infections?
- Upper Respiratory tracts
- Lower resp tracts infections
What are upper respiratory tract infections (URTIs)?
- Common, often mild and viral in aetiology
- Secondary bacterial/fungal infections are common
- affect lower layers of tissues that cause further symptoms.
Virulence- ability to cause disease
What are some common viral URTIs?
- Rhinovirues (common cold) - >100 types
– responsible to 80% of URTIs - coronaviruses (10-15%) - 7 human types
- Human parainfluenza viruses (HPIVs); type 1-4 (5-15%)
- Respiratory syncytial virus (5%)
- Adenoviruses (<5%)
- Enteroviruses e.g. , coxsackieviruses, echoviruses (<5%)
What causes Pharyngitis/Tonsillitis?
- Viruses (adenoviruses)
- Bacteria - strep pyogenes
What is infectious mononucleosis?
- Glandular fever
- Non aetiological diagnosis - cannot always determine causation
- Pharyngitis, lymphadenopathy, sore throat. fever and malaise
- EBV, cytomehalovirus, toxoplasma gondii and HIV
- presents with atypical mononuclear cells in peripheral blood (larger than usual)
Describe how EBV can undergo latency and reactivation following primary infection
Primary infection
* Viral entry/ replication promotes growth transformation of B cells
* Blasting b cell - priming of naiive t cells promotes EBV specific response
* Latent infection = Resting b CELL
* Persistent infection due to viral shedding
What is sinusitis?
- Inflammation of sinuses due to infection
- usually following viral infection or post-viral bacterial infection
- Charactetised by facial pain/pressure, nasal obstruction and nasal discharge
- Post natal drip from sinusitis - irritates larynx and may cause a persistent cough
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What are Lower resp tract infections (LRTIs)?
e.g :
- bronchitis, bronchiolitis, Tb and pneumonia
- Potentially life threatening
- often viral/bacterial in aetiology
Examples of viral LRTIs
- Influenza viruses (A-C)
- HPIVs (types 1-3)
- RSV (A and B)
- SARS-Cov-2 (COVID-19)
- Chicken pox pneumonia (variceella zoster virus )
- Measles virus (MeV)- giant cell pneumonia - immunocompromised children
- Cytomegalovirus (CMV)- Pneumonia - resp failure - immunocompromised as part of normal flora
- SARS- Cov-1and MERS- CoV- acute resp distrezss syndrome
What is the structure of influenza A?
- enveloped, spherical, 90-100nm diameter
- Spike proteins - Haemagglutinin (HA) and Neuraminidase (NA) - different types of influenza dependent on type of spike protein on it
- Genome - ssRNA- 8 segments - encode 10-14 proteins but have a big impact
What is the epidemiology of influenza A?
- Affects humans, horses, birds , pigs etc
- Displays extensive xoonosis
- Natural reservoir in birds
- Major pandemics
- Transmission via close contact ; inhalation
- Facillitates secondary bacterial infections
What are the symptoms of influenza A?
- Flue like illness
- Respiratory tract symptoms - rhinitis, cough, SOB
- Systemic symproms, fever , headache, myalgia
What is the pathogenesis of influenza A?
Pneumotropic virus - infects cells lining the resp tract down to alveoli
(Cyto)lytic infefction - strips off surface resp epithelium
- removes 2 innate defence mechanisms, mucous secreting cells and cilia
- cytokine production; circulates in blood (not the birus)
- ILA- general defence - ‘flu-like’ symproms
- Interferons- antiviral defence
What are some complications of Influ A?
Pneumonia :
- primary viral influenza pneumonia - lymphocyte infiltration (mononuclear)
- Secondary bacterial pneumonia - macrophage/neutrophilic infiltration (polymorphonuclear)
- Cardiovascular complications
- Myocarditis
- CNS complications - encephalitis
State high risk patients of influ A
Patients w:
- Lung disease
- CVDs
- Renal disease
- Endocrine disease
- Immunodeficiency
- Liver disease
- Anyone>65 years
- Obese, pregnant women, children
