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
What are influ A antigenic subtypes?
- Classsified on HA and Na - subtyped numerically as HxNy
What is antigenic variation?
-Antigenic shift:
sudden dramatic change resulting in new subtype
What is the prevention and treatment of influ A?
Infection monitoring
- Vaccination :
- inactivated
- recombinant
- live attenuated
-Medical treatment
- O2 therapy
- Anti0viral drugs
- Antibiotics
- ITU support
What is Resp Syncytial Virus (RSV)?
- Leading cause of LRTIS in infants
- Also found in elderly parients
- 33 million cases and 160-190,000 deaths worldwide annually
- Incubation of 4-5 days and spreads easily
- No animal reservoir
- Linked to asthma and bronchiolitis
What is the structure of RSV?
- Variants : RSV-A and RSV-B (antigenetically distinct ) - multiple genotype isolates
- Enveloped. 120-200 nm in diameter. Can be spherical, filamentous and asymetric
What is the pathogenesis of RSV?
- Cytopathology linked to viral loaf
- Block cell cycle processes to maximise viral replication
- Disrupts viliated epithelial cells
- Inflammationa dn mucosal oedema
- Promotes monocyte lunf infiltration
- Syncytia formation
- Sloughed cells, immune modulators and mucous leads to obstruction
What are symptoms and disease of RSV?
- Causes restriction, obstruction, runny nose, SOB, wheezing, hypoxia, pneumonia and bronchiolitis
- Developement of asthma linked to RSV infection
- Mostly causes mild-moderate disease (2-3 % require hospitilisation)
- Low mortality (0.5%)
- congenital heart disease
- congenital lung diseasse
- immunodeficiency
Whata re risk factors of RSV?
Age- young individuals and elderly
Gender
Vit D deficiency
Genetic polymorphisms in innate and adaptive immune response (genes,surfactant protein genes and host receptor genes- increase susceptibility)
- Environmental factors :
- exposure to cig smoke, smoking directly afffects airway epithelial cells, including necrosis
- Air pollution
- Time of the year - seasonal infection
What is the prevention and treatment of RSV?
-Infection monitoring
Vaccination
Medical treatment:
- Hydration and antipyretics
- Oxygen therapy
- RSV neutralising antibodies
- ITU support
