Tracing the bug

Dr. Shivani Vakilwala, Medical officer 

LET’S TRACE THE BUG

     CORONAVIRUS OUTBREAK – the two words we have been hearing and seeing on TV screens every day. A zillion social media messages flooding everyone’s phones. But how much do we really know about it? Let’s take a moment to trace the bug and dig deep into past. Perhaps that will give some insight into its future. 

The Coronavirus is an ssRNA enveloped virus with protein spikes (it is because of these protein spikes that it gets its name, these spikes make it look like a crown and hence the term CORONA, which literally means crown in Latin). These spikes help the virus bind to ACE2 receptors on Type 2 pneumocytes in the lungs, and the virus on binding takes over the cellular machinery to make several copies of itself following which it spreads into the surrounding mucous leading to symptoms from a common cold to Severe Acute Respiratory Distress Syndrome.

The structure of the Coronavirus

Image source : https://www.extremetech.com/internet/305449-johns-hopkins-tracks-coronavirus-outbreak-in-real-time

Three of the seven coronaviruses cause severe respiratory infections in humans and have caused major outbreaks of deadly pneumonia in the 21st century:

  1. SARS- CoV2 – which is the novel Coronavirus; identified as the cause of Coronavirus Disease 2019 (COVID-19) 
  2. SARS-CoV1 which caused an outbreak of Severe Acute Respiratory Syndrome (SARS)
  3. MERS-CoV which caused the Middle Eastern Respiratory Syndrome (MERS)

Our focus in this article is going to be on the first two; COVID 19 and the SARS CoV1.

COVID 19 is a Beta coronavirus which was discovered in 2019 in Wuhan, China. It originated at a marketplace selling animals for consumption in Wuhan, increasing evidence for its zoonotic origin. 

Origin: Most likely originated from bats with the intermediate carrier being a Pangolin (which is heavily trafficked as their scales have human skin like properties).  

Mode of Infection: Droplet infection mainly, but also spreads via infected surfaces (fomites).

R0: 2-4 (similar to influenza)

Symptoms: 45% febrile, 70% have cough, 20-40% dyspnoea, 15% URI symptoms, 10% GI symptoms of diarrhoea and/or vomiting; severe infections (in the elderly and immunocompromised) may have Pneumonia.

Incubation period: 2 to 14 days.

Confirmation of the Diagnosis: Real-Time Polymerase Chain Reaction test.

Treatment:
Isolate and send sample for PCR at earliest (takes days), Fluid sparing resuscitation, Oxygen. Notify the health authorities.
Intubate early under controlled conditions, depending on patient status, ventilatory support (avoid NIPPV as this aerosolizes the virus and increases provider risk of infection, unless individualized reasons exist – like COPD, etc.), +/- empiric antibiotics.

Investigational therapies: Remdesivir (blocks RNA dependent polymerase), Chloroquine (blocks viral entry in endosome), Tocilizumab (blocks IL6), and Corticosteroids (reduces inflammation). 

Prevention:
Careful hand washing (20+ seconds) with soap or 70% alcohol based sanitizers and scrubbing.
Avoid touching the T-zone of your face which includes touching the eyes, nose and mouth.
Avoid raw or undercooked animal products like raw meat, milk or animal organs.
Healthcare providers should exercise Standard + Contact precautions. They must use N95 masks and protective eyewear (shields) for procedures where aerosolization occurs (NIPPV, intubation, extubation, suctioning, etc). 

Mortality rate: As of 20th March 2020, 265,976 people have been infected and there have been over 11,186 deaths globally.

Velocity of the virus (Days before the first 1000 people are infected): 48 days.

Symptoms of the SARS CoV2 infection      

 Image source: Wikipedia.org

SARS CoV1 – It was first reported in 2002 in Southern China.

Origin: Believed to have spread from bats and intermediate carrier being Civets.

Mode of Infection: Transmission mainly between humans through close contact.

Symptoms: Fever, dyspnoea, sore throat, myalgia, diarrhoea.

Mortality rate: 8,437 cases with 774 deaths. Mortality rate of about 9.63%.

Velocity of the virus (Days before the first 1000 people are infected): 130 days.

Table of clinical and radiological differences between SARS CoV1, MERS and COVID19

Image source : https://www.eurekalert.org/multimedia/pub/225688.php

References:

  1. Osmosis.org
  2. Cdc.gov
  3. msdmanuals.com
  4. https://www.nejm.org/doi/full/10.1056/NEJMc2004973

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