Severe acute respiratory syndrome-related coronavirus (SARSr-CoV) is a species of coronavirus, it is a member of the genus Betacoronavirus and subgenus Sarbecoronavirus. SARSr-CoV is an enveloped positive-sense single-stranded RNA virus that enters its host cell by binding to the ACE2 receptor, then infects humans, bats and certain other mammals.  Bats are a major reservoir of many strains of SARS-related coronaviruses. Only recently have strains of SARS-related coronavirus evolved and made the cross-species jump from bats to humans, as in the case of the strains SARS-CoV and SARS-CoV-2. 
SARS-CoV and SARS-CoV-2 have caused outbreaks of severe respiratory diseases in humans: SARS-CoV (or SARS-CoV-1), which caused an outbreak of severe acute respiratory syndrome (SARS) between 2002 and 2003, and SARS-CoV-2, which caused the 2019–20 pandemic of coronavirus disease 2019 (COVID-19).
In this article, we mainly discuss SARS-CoV, including structure, the important proteins, infection mechanisms, infection Symptoms, transmission, Diagnosis and Treatment. If you want to know more about SARS-CoV-2, please click 2019 Novel Coronavirus.
The Structure of SARS-CoV
The SARS-related coronavirus is an enveloped, positive-sense, single-stranded RNA virus. Its genome is about 30 kb, which is one of the largest among RNA viruses.
The viral envelope consists of a lipid bilayer where the membrane (M), envelope (E) and spike (S) proteins are anchored.  The spike protein's interaction with its complement host cell receptor is central in determining the tissue tropism, infectivity, and species range of the virus.  Inside the envelope, there is the nucleocapsid, which is formed from multiple copies of the nucleocapsid (N) protein. The lipid bilayer envelope, membrane proteins, and nucleocapsid protect the virus when it is outside the host. 
Follows the replication strategy typical of the coronavirus subfamily, the primary human receptor of SRAS-CoV is angiotensin-converting enzyme 2 (ACE2), first identified in 2003. 
Figure 1. The Structure of SARS-CoV
Disease Caused by SARS-CoV
Severe acute respiratory syndrome (ARS) is the disease caused by SARS-CoV. The illness usually begins with a high fever, sometimes associated with chills or other symptoms, including headache, general feeling of discomfort, and body aches. Some people also experience mild respiratory symptoms at the outset. Diarrhea is seen in approximately 10% - 20% of patients. After 2 to 7 days, SARS patients may develop a dry, nonproductive cough that might be accompanied by or progress to a condition in which the oxygen levels in the blood are low . In 10% - 20% of cases, patients require mechanical ventilation. Most patients develop pneumonia.
In the SARS outbreak of 2003, about 9% of patients with confirmed SARS-CoV infection died.  The mortality rate was much higher for those over 60 years old, with mortality rates approaching 50% for this subset of patients.In the SARS outbreak of 2003, about 9% of patients with confirmed SARS-CoV infection died. The mortality rate was much higher for those over 60 years old, with mortality rates approaching 50% for this subset of patients.
Transmission of SARS-CoV is primarily from person to person.
SARS-CoV is thought to be transmitted most readily by respiratory droplets produced when an infected person coughs or sneezes. Droplet spread can happen when droplets from the cough or sneeze of an infected person are propelled a short distance through the air and deposited on the mucous membranes of the mouth, nose, or eyes of persons who are nearby.
The virus also can spread when a person touches a surface or object contaminated with infectious droplets and then touches his or her mouth, nose, or eyes.
In addition, it is possible that SARS-CoV might be spread more broadly through the air or by other ways that are not now known.
Diagnosis of SARS-CoV Disease
The diagnosis of SARS-CoV disease and the implementation of control measures should be based on the risk of exposure.
In the absence of person-to-person transmission of SARS-CoV anywhere in the world, the diagnosis of SARS-CoV disease should be considered only in patients who require hospitalization for radiographically confirmed pneumonia and who have an epidemiologic history that raises the suspicion of SARS-CoV disease.
Once person-to-person transmission of SARS-CoV has been documented in the world, the diagnosis should still be considered in patients who require hospitalization for pneumonia and who have the epidemiologic history described above.In addition, all patients with fever or lower respiratory symptoms should be questioned about whether within 10 days of symptom onset they have had close contact with someone suspected of having SARS-CoV disease, or a history of foreign travel to a location with documented or suspected SARS-CoV, or exposure to a domestic location with documented or suspected SARS-CoV, or close contact with an ill person with such an exposure history.
Available laboratory testing for SARS-CoV include antibody testing using an enzyme immunoassay (EIA) and reverse transcription polymerase chain reaction (RT-PCR) tests for respiratory, blood, and stool specimens. Initial diagnostic evaluation to look for an alternative diagnosis in suspected SARS-CoV patients should be performed as clinically indicated, and may include:
- Chest radiograph
- Pulse oximetry
- Complete blood count with differential
- Blood cultures
- Sputum Gram's stain and culture
- Testing for viral respiratory pathogens, notably influenza A and B and respiratory syncytial virus
- Specimens for Legionella and pneumococcal urinary antigen testing
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