Respiratory Infections 5 Flashcards
Pneumonia classification: type of microbe
- Typical = Gram Positive and Gram Negative Bacteria
* Atypical = Viruses, Atypical Bacteria, Fungi, Parasites
Pneumonia classification: exposure
Community acquired pneumonia
Nosocomial
- hospital acquired pneumonia: >48 hours post-admission
- ventilator associated pneumonia: >48 hours intubation
- Healthcare Associated Pneumonia HCAP <3 months post healthcare facility (hospital, long term care facility)
Pneumonia Classification: source of microbe
Aspiration Pneumonia: microbes originate from GI tract (vomiting, impaired gag reflex, intubation)
Broncho-pneumonia/Lobar
typical pneumonia with focal densities
Interstitial pneumonia
atypical pneumonia with diffuse, hazy infiltrates
Acute Exacerbated Chronic Bronchitis
reactivated inflammation in patient with chronic lung condition (CF, COPD)
Necrotizing/Cavitary Pneumonia
focal liquification, region of decreased opacity due to necrosis
Viral pneumonia
- normal or increased lymphocytes
- tachypnea and wheezing
- no pleuritic Chest pain
- no CNS features
- hyperinflation with bilateral interstitial infiltrates
Bacterial pneumonia
- high fever and chills
- dyspnea and productive cough
- pleuritic chest pain
- anxiety and delirium
- lobar consolidation +/- pleural effusion
- increased granulocytes
Most common viral causes of atypical pneumonia
SARS-CoV2
Influenza
SARS-CoV2: Biology
Family - Coronaviridae SARS-CoV2 =Severe Acute Respiratory Syndrome Coronavirus • Enveloped ss(+)RNA virus • Spike protein – vaccines • RDRP–antivirals
How to diagnose SARS-CoV2
- Rapid Antigen ELISA, lateral flow
* Suggestive of active - NAAT (RT-PCR)
* Confirmatory for active infection - Serology - EIA
- IgM -> Suggestive of active infection
- IgG -> Anti-nucleocapsid is indicative of past infection
Transmission of sars cov2
Aerosol droplet, Airborne
Who is high risk for sars cov2
• Unvaccinated ~97x risk of death
• Elderly,Hypertension,Obesity,Diabetes
Smokers, people with other respiratory illnesses
Prevention against sars cov2
Moderna,Pfizer
• mRNA subunit vaccines encoding Spike protein
• Require 2x doses to yield high efficacy
• Booster is recommended post-Omicron
Johnson-Johnson,AztraZeneca
• AdenovirusvectorswithsubunitDNASpikeprotein
Shift
Sudden phenotypic change of virus from gene rearrangement with co-infection with 2 strains
Drift
Gradual accumulation of random point mutations
Alpha, Delta and Omicron BA.1 and Omicron BA.2 emerged from which process
Drift
New strains of Omicron XE, XR, etc. emerged from
Shift gene recombination events with Omicron BA.1 and Omicron BA.2
SARS-CoV2 Pathogenesis part 1
Spike Protein binds to ACE2 host receptor
SARS-CoV2 Pathogenesis part 2
- Viral replication
Virus initially downregulates Interferon-α
Virus replicates in interstitial tissue, Syncytia formation
Virions spread systemically, replicating in CD4+ T cells, cardiac, hepatic, renal tissue
SARS-CoV2 Pathogenesis part 3
- cytokine storm
- bradykinin activation
- Vascular damage accumulates on major organs
What’s this showing
SARS-CoV2: Pathogenesis Syncytia Formation
What is a syncytia
A single cell or cytoplasmic mass containing several nuclei, formed by fusion of cells or by division of nuclei
Clinical Presentation: COVID-19
- Onset~3-14days
- Loss smell (anosmia)
- Loss of taste (ageusia)
- Interstitial pneumonia progressing to Acute Respiratory Distress Syndrome ARDS is most common cause of mortality
- Viral replication in any tissue with ACE2R plus immune-mediated inflammation can cause multi-organ tissue damage
What is seen on COVID-19 Imaging
- Ground-glass opacities are most common.
* Consolidation can be observed, esp. with superinfection
COVID-19 Complications
- Interstitial Pneumonia -> ARDS -> Death
- Secondary Bacterial Pneumonia Superinfections
- Sepsis, Coagulopathy
- Multi-System Inflammatory System in Children (MIS-C)
- Long COVID aka Post-Acute Sequalae SARS-CoV2 Infection (PASC)
Influenza: Biology
- Family–Orthomyxoviridae
- Enveloped
- Segmented ss(-)RNA
- Haemagglutinin (HA) glycoprotein
* Viral Attachment Protein - Neuraminidase (NA) surface enzyme
* Release of new virions by sialic acid cleavage - Based on Matrix (M-protein) and nucleoproteins
- Rapid Antigen test can determine Type A/B
Influenza replication
- Hemagluttanin does attachment: binds sialic acid
- virus enters by endocytosis
- M2 - uncoating
- segmented ss(-)rna is replicated by RNA dependent RNA polymerase
- neuraminidase cuts sialic acid releasing the virus
Type A Influenza
Zoonotic!
• More pathogenic than Type B or C.
• Reservoir: humans, birds, swine, horses, seals.
• Antigenic Shift cause pandemics (ex. Swine flu H1N1 in 2009)
• Antigen Drift cause localized annual epidemics
Type B and Type C influenza are human-restricted cause milder symptoms and undergo __________ only
Antigenic drift only
How is Influenza transmitted
Aerosol droplet: human-to-human, animal-to-human (Bird & Pig)
Influenza type A H1N1 has tropism for
humans, pigs, horses and ducks
What caused the global swine Flu Pandemic
Genetic reassortment shift events
- A host animal was co-infected with more than 1 strain and the new virions are packaged with a new combination of genome segments.
- Introduction of new HA type (H1) on human-adapted virus to immunologically-susceptible population = pandemic
Influenza Virus Prevention
Annual drift necessitates yearly booster
Live, attenuated nasal spray
• Induces strong IgA response
• Recommended for > 2 years, < 50 years
Killed, Inactivated shot
• Induces IgG response
• Recommended for health care workers, age extremes, immunocompromised
Influenza Virus Pathogenesis
- Influenza HA targets sialic acid on mucus secreting, ciliated cells and replicates in respiratory tract
- Infection in lower respiratory tract leads to cytokine storm and desquamation (shedding) of bronchial epithelium cells
- Virus infection facilitates primary viral pneumonia and onset of secondary bacterial infections (most common cause of Flu-associated death)
Clinical presentation of the flu
- Preceded by or with a cold
- Dry sputum cough
- Dyspnea
- High fever
- Intense muscle pain
- GI symptoms are more common in children
Influenza Complications
Secondary Bacterial Superinfections including sinusitis, otitis media (children), typical bacterial pneumonia (elderly) = MOST COMMON CAUSE of “Flu-associated” deaths
COVID-19 and Flu prognosis
▪ Can be range from mild to life-threatening, especially hypoxia
▪ Approximately 1/3 COVID-19 patients experience symptoms for months
▪ Antivirals for Influenza will shorten the course if administered <24 hours after onset
Is it COVID, Common Cold or Flu?
