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An Overview of the Novel Coronavirus (COVID-19)

While our formal teaching rounds at @WCHospital are on hiatus as a result of the current #COVID-19 pandemic, I thought I would compile some information to provide an overview of what we know about the virus and the pandemic thus far. This is based on our current knowledge as of March 13th, 2020. Hopefully you find it helpful! Please contact me if you have any comments or suggestions for improvement at cmr@wchospital.ca. – Leora

Overview

  1. What is COVID-19?
  2. Epidemiology
  3. Illness Severity
  4. Transmission
  5. “Flattening the Curve”
  6. Presentation and Diagnosis
  7. Management

1. What is COVID-19?

  • COVID-19 aka SARS-CoV-2 is a non-segmented, positive sense RNA betacoronavirus that is part of the family of coronaviruses.
    • Other coronaviruses include those that cause the common cold (unless immunocompromised), MERS and SARS.
    • COVID-19 is most closely related to SARS.
  • COVID-19 binds with high affinity to ACE2 on type II found in alveolar cells and intestinal epithelial (Hamming 2004).
    • Read more about the pathophysiology of COVID19 here
  • The virus is mutating, which may be contributing to changes in virulence and transmission. Ongoing phylogenetic mapping of new strains can be seen here.
  • Animal resevoir likely bats
  • Associated with severe disease and poor outcomes in those who are immunocompromised and with comorbidites
Image result for covid microscopy

2. Epidemiology

  • COVID-19 is a global pandemic that began in Wuhan, China with subsequent significant outbreaks in Italy, Iran, South Korea etc. with worldwide spread
  • In terms of severity, the WHO estimates a moderate to very severe pandemic, based on COVID-19’s transmissibility and clinical severity (See chart below for comparison of transmissibility and clinical severity)
Image result for severity covid who

3. Illness Severity

  • The case fatality rate (CFR) still unknown
    • The true number of infected is unknown
    • Best estimates CFR = 0.3–1% (but may be as high as 3% and higher in those who are older and with comorbidities)
      • Influenza A CFR = 0.1%
  • Severity data from China:
    • 80% mild (pneumonia and non-pneumonia)
    • 12-14% severe
      • hypoxia, >50% lung involvement within 24-48 hr, PaO2/FIO2 ratio <300, RR ≥30
    • 6-8% critical
      • respiratory failure, septic shock, and/or multiple organ dysfunction/failure)
    • Guan et al, Feb 2020

4. Transmission

  • Transmitted through respiratory droplets (Rio, 2020) and contact transmission (e.g., contaminated surfaces).
  • Airborne precautions recommended for invasive respiratory procedures (i.e., suctioning, bronchoscopy and intubation/extubation)
  • Pre-symptomatic transmission reported (Tindale et al, 2020)
    • Per the WHO, viral shed may occur 24-48 hours prior to symptom onset but this “does not appear to be a major driver of transmission” (WHO, March 6)
  • Reproductive number, R0: (reproductive number, the number of secondary infections spread by one primary case; R0>1 means that the pathogen will spread)
    • R0 = 2.0-2.5 in the early stages in China
      • Prior to comprehensive control measures (Li, 2020)
      • More recent estimations vary.
    • R0 for influenza = 1.5
  • Incubation period:
    • Range: 0-14 days
    • Median: ~5 days (Lauer, 2020)
      • 97.5% of those who develop symptoms doing so within 11.5 days 

5. Flattening the Curve

Flattening the curve of the epidemic refers to slowing down the rate in which people get sick through public health measures. Even if the total number of cases in an epidemic cannot be reduced, spreading out the number of new infections over time reduces demands on the health care system to ensure that we do not exceed its capacity.

For example, below is a figure demonstrating the simulated effects of social distancing measures on the epidemic curve. The red curve demonstrates what would happen without early measures to slow the rate of infection, while the second blue curve shows how early social distancing can flatten the curve and slow the rate of infection. However, this graph also shows the risk of resurgence if public health interventions are stopped too early.

Image result for simulation transmission covid 19
The Lancet
  • Other protective public health measures include: cancelling mass gatherings, self-quarantines, self-isolation and closing schools.

6. Presentation and Diagnosis

  • Symptoms:
    • Cough (60-80%)
    • Fever (45-90%; large variation in studies)
      • Note that the absence of fever does not exclude COVID-19.
    • Dyspnea (20-40%)
    • URTI symptoms (15%)
    • GI symptoms (10%)
Image result for covid vs flu symptoms canada chart
Most common symptoms in China, up to February 22, 2020
  • Labs:
    • Lymphopenia is common (83%)
    • Mild transaminitis, elevated LDH
    • Elevated CRP
    • May develop signs of DIC (poor prognosis; Tang et al., 2020).
    • Microbiology: PCR testing is diagnostic, but low sensitivity
      • New diagnostic tools in development
  • Radiology:
    • CXR:
      • Patchy peripheral opacities, increased involvement in more severe disease (Shi et al., 2020)
    • CT:
      • Ground glass opacities (bilateral, peripheral)
      • Progression to consolidation (lower lung or multifocal) and crazy paving pattern (peaks around 9-13 days) (Zhou et al., 2020)
      • High specificity (Bai, 2020)
      • Less likely to have pleural effusions
Silverstein et al., 2020
Image result for covid19 ct scan article
Guan et al., 2020

7. Management

  • Isolation:
    • Assume proper precautions: droplet+ contact including eye protection. Airborne precautions if there is a need for invasive respiratory procedures (e.g., intubation)
    • Ensure good hand hygiene
    • Limit visitors
  • Test for COVID-19 and notify public health and relevant authorities
  • Supportive care, fluid sparing resuscitation
  • Oxygen and mechanical ventilation as needed
  • Consider empiric ABx e.g., ceftriaxone 1g IV q5d if concern for bacterial coinfection
  • Standard ARDS Tx (The 7 Ps)
  • Steroids may prolong viral shedding, however may have benefit in ARDS. Generally not recommended (Wu et al., 03/13)
  • Potential anti-viral treatments (under study; generally not recommended without expert consultation or as part of RCT)
  • Patients who survive the initial phases may require prolonged ventilator support (Zhang 2020)
  • Public health measures are key: social distancing, cancelling mass gatherings etc.

Thanks for reading if you made it to the end! Again, please contact me if you have any suggestions for improvement at cmr@wchospital.ca

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