SARS EPIDEMIC

SARS EPIDEMIC

In November 2002, many cases presented with Atypical pneumonia in china and around the world. This was identified as epidemic by WHO ( World Health Organization) .

Most patient developed Acute respiratory distress that’s why it’s called Severe Acute Respiratory syndrome (SARS).

The total number of reported cases of SARS worldwide reached 8437 in 29 counties.More than 5000 cases were reported in the People’s Republic of China and more than 200 cases in Canada and Singapore

SARS-COV is the name of the virus that lead to this epidemic.

What is SARS-COV virus ?

SARS-COV is corona virus , Which is RNA viruses , positive sense , enveloped with crown like spikes.

The SARS virus

Corona virus belong to Coronaviridae family and it have 4 subgroups :AlphaBetaGammaDelta.
Alpha and Beta groups are the only groups can infect mammals.


There is seven species of corona virus that can infect humans :

  1. HCoV-NL63
  2. HCoV-229E
  3. HCoV-OC43
  4. HKU1
  5. SARS-CoV
  6. MERS-CoV
  7. SARS-CoV -2


The Origin of SARS-CoV:

All corona viruses originate from animals, especially from bats and rodents. SARS-COV transmitted directly to humans from civet cats.

Pathogenesis of SARS:

SARS-COV virus bind to cells that express ACE-2 on their surface , ACE2 is found on both endothelial and endothelial cells.

Also, SARS-COV virus depend on proteolytic enzyme called ” cathapsin L” which expressed by epithelial cells.

SARS-COV virus can also bind to surface protein L-sign and DC-sign.
L-sign found on the liver and lymph node, DC- sign found on the dendretic cells and macrophages.

Both structural and non-structural component of SARS-COV virus will be caught in the serum of infected human, these particles will induce apoptosis of healthy cells (Mechanism is not well known).

SARS-COV virus have the potential to infect immune cells of both innate and adaptive immune system. Destruction of lymphocytes and leukocytes will help in up-regulate the expression of chemokines and cytokines, especially schematic ones that are able to destroy pathogens or cells and this is actually what causes the severe damage of the lungs and called ” Cytokines storm”.

SARS-COV Transmission :

Initial spread of SARS-COV virus from animal to human is highly probable originate from cross-species jump from civet cat to human by direct contact.

SARS-COV virus transmitted from human to human through close contact with infected person and indirectly via contaminated air and surfaces.

Droplet spread can happen when shed from respiratory secretion via cough or sneeze within short distance (up to 3 feet). It is possible that SARS-COV spread through fecal-oral route and airborne spread.

SARS-COV incubation period :

Incubation period is the duration between first exposure to the virus and when the sign and symptom of disease caused by the virus first appear.

SARS-COV virus incubation period is usually 2 to 9 days, the reported median incubation period is 5.2 days.

according to a study was found that shorter incubation period is associated with greater severity of the disease.

presentation of SARS:


Most SARS patient suffer from respiratory illness, usually begin with a sudden onset of high fever, headache and fatigue. Most patient will develop pneumonia and can be lethal for severe cases.

  • Fever > 38ºC (100%)
  • Cough  (66%)
  • Chills  (52%)
  • Myalgias  (49%)
  • Dyspnea  (46%)
  • Headache  (39%)

some patients also reported gastrointestinal symptoms, such diarrhea. some patient present with Sore throat ,rhinorrhea ,cough ,dyspnea and pleuritic pain .

10.9% average death rate in most of severe cases, it is difficult to make an accurate prognosis because there is no cure.

Imaging of SARS patient

SARS patient radiography range from normal to diffuse interstitial infiltrate (ARDS)

CT scan show ground glass appearance in SARS patient

SARS-COV Lab test :

PCR TEST

polymerase chain reaction test is essential to detect genetic material of SARS-COV virus patient’s blood, stool or nasal secretion.

serologic test
  • SARS virus antibodies
  • depressed total lymphocytes
  • elevated lactate dehydrogenase (LDH)
  • elevated alanine aminotransferase
Viral culture (isolation)

SARS Treatment :

There is no specific treatment for illnesses caused by SARS-COV but supportive care help in relieving symptoms , this include :

  • Hydration
  • Antipyretic
  • Analgesics
  • Respiratory support
  • Antibiotic ( for bacterial superinfection)

Patients are usually given :

– Broad spectrum Antibiotics
-Antiviral agents (Ribavirin)

it block processing of the viral replicase polyprotein , So it prevent RNA replication

-Immunomodulatory therapy (corticosteroid)

it is very powerful and affect the entire body, it have anti-inflammatory and immunosuppressive effect so it significantly improve fever and lung infiltrate.

SARS-COV prevention:

There is no vaccine available to prevent SARS-COV infection, vaccine and monoclonal antibodies remain in development. http://europepmc.org/article/MED/17416434

Proper infection control is recommended by WHO when caring for suspected or confirmed MERS cases including:

  • standard and droplet precautions when caring for patients with acute respiratory tract infections .
  • Contact precautions and eye protection when caring for probable or confirmed cases of MERS-CoV infection.
  • Airborne precautions when performing aerosol-generating procedures.


RESEARCH RELATED TO THIS TOPIC :

  1. https://www.uptodate.com/contents/severe-acute-respiratory-syndrome-sars/abstract/1
  2. http://diseases.emedtv.com/sars/sars-prognosis.html
  3. https://www.cdc.gov/sars/about/faq.pdf

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