Coronavirus disease 2019 (COVID-19) - Structure

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Origin - City of Wuhan, Hubei Province, Central China

In early December 2019, numerous people with unknown causes of pneumonia were observed in Wuhan City, Hubei Province, Central China. Then, scientists studied the genome of the virus and named 'coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). 

The primary (main) site of infection- The virus was identified in the respiratory tract of the patients 

Structure - SARS-CoV-2 is an enveloped, non-segmented, positive-sense RNA virus that is within the sarbecovirus, ortho corona virinae subfamily found in humans, and other mammals. It's about 65-125nm in diameter, containing single strands of RNA and provided with crown-like spikes on the outer surface. 
Structurally, it has four main proteins
  1. Spike (S) glycoprotein
  2. Small envelope (E) glycoprotein
  3. Membrane (M) protein 
  4. Nucleocapsid (N) protein
 

Each protein has its own function. for example, S glycoprotein is found in the outer portion of the virus, and it binds with the host (human/animal) through angiotensin-converting enzyme 2 (ACE2) expressed in lower respiratory tract cells. 

Mode of transmission - 
1. Direct inhalation of infected droplets (produced during coughing or sneezing by infected person) and direct contact with surfaces and fomites soiled by infected respiratory secretions

2. Special situations associated with aerosol generation (cardiopulmonary resuscitation, endotracheal intubation, open suctioning, bronchoscopy, nebulisation and use of non-invasive ventilation) can lead to aerosol generation and spread

Duration - On the surfaces maybe a few hours to a few days; the survival duration is likely to be considerably low at a higher temperature and low humidity conditions, but debatable.

Symptoms - Fatigue, fever, dry cough, myalgia (muscle pain) and dyspnoea (difficulty in breathing), with less common symptoms being nasal congestion, headache, runny nose, sore throat, vomiting and diarrhoea.

Diagnosis - The virus in the respiratory specimen (nasopharyngeal and oropharyngeal swab/ endotracheal secretions or bronchoalveolar lavage) by using specific RT-PCR


Reference- 
1. Coronavirus envelope protein: current knowledge. Virol J. 2019;16:69
2.Coronavirus disease 2019 (COVID-19): current status and future perspectives
3.COVID-19 in Children: Clinical Approach and Management


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