Causes

• SARS is caused by the SARS coronavirus (SARS-CoV-1), which belongs to the Coronaviridae family.
• The virus likely originated from bats, spread to civets (an intermediate host), and then jumped to humans.
• It spreads via:
  • Respiratory droplets (when an infected person coughs or sneezes).
  • Direct contact with an infected person.
  • Touching contaminated surfaces and then touching the mouth, nose, or eyes.

Epidemiology

• First outbreak: November 2002, Guangdong, China.
• Global spread: Reached 29 countries.
• Total cases: Over 8,000 cases worldwide.
• Deaths: 774 people (case fatality rate ~9.6%).
• High-risk groups: Healthcare workers, elderly individuals, and people with weakened immune systems.
• Contained by July 2003: Due to strict quarantine measures and public health interventions.

Life Cycle of SARS-CoV-1

• Attachment & Entry – The virus binds to the ACE2 receptor on lung cells and enters the host cell.
• Replication – The virus takes over the cell’s machinery to produce new viral proteins.
• Assembly & Release – The new virus particles are formed and released to infect more cells.
• Immune Response & Inflammation – The immune system reacts, leading to fever, lung inflammation, and possible cytokine storm (overreaction of the immune.

Pathology (How SARS Affects the Body)

• SARS primarily affects the lungs, causing diffuse alveolar damage (injury to lung tissues).
• Leads to pulmonary edema (fluid buildup in the lungs).
• The immune system’s overreaction (cytokine storm) can worsen lung damage.
• Can also affect liver, kidneys, and intestines in severe cases.

Signs and Symptoms

• Incubation period: 2–14 days.
• Early symptoms (like flu):
  • High fever (>38°C)
  • Fatigue
  • Chills
  • Muscle pain
  • Headache
• Respiratory symptoms (after a few days):
  • Dry cough
  • Shortness of breath
  • Hypoxia (low oxygen levels)
  • Pneumonia
• Some patients have gastrointestinal symptoms like diarrhea and abdominal pain.

Investigations (Diagnosis Tests)

• Lab Tests:
  • RT-PCR test (to detect viral RNA in respiratory samples).
  • Serology tests (to detect antibodies like IgM and IgG).
  • Blood tests:
    • Lymphopenia (low white blood cell count) is common.
    • High CRP (C-reactive protein) indicates inflammation.
• Imaging:
  • Chest X-ray: Shows lung infiltrates (signs of pneumonia).
  • CT scan: Shows ground-glass opacities (fluid buildup in lungs).
• Other Tests:
  • Blood culture (to rule out bacterial infections).

Differential Diagnosis

• COVID-19 (SARS-CoV-2) – Similar symptoms but different virus.
• Influenza (flu) – Can also cause fever and pneumonia.
• Community-acquired pneumonia – Bacterial pneumonia with similar chest X-ray findings.
• Middle East Respiratory Syndrome (MERS-CoV) – Another coronavirus with a high fatality rate.
• Legionnaire’s disease – A bacterial infection that also causes pneumonia.
• Tuberculosis (TB) – Causes chronic cough and lung damage.

Management (Treatment and Care)

• There is no specific antiviral treatment for SARS, so management focuses on supportive care:
• Supportive Care:
  • Oxygen therapy (for breathing difficulty).
  • Mechanical ventilation (for severe cases with ARDS).
  • IV fluids to prevent dehydration.
• Medications (Experimental use during outbreak):
  • Antivirals like Ribavirin and Lopinavir/Ritonavir were tested but not very effective.
  • Corticosteroids were used to reduce inflammation but had mixed results.
  • Immunomodulators (e.g., Interferon) were studied to boost the immune response.
• Infection Control Measures:
  • Strict isolation of infected patients.
  • Quarantine of close contacts for 21 days.
  • Healthcare workers using personal protective equipment (PPE) (masks, gloves, gowns).

Complications

• Acute Respiratory Distress Syndrome (ARDS) – Life-threatening lung failure.
• Septic Shock – Severe blood infection leading to organ failure.
• Multiorgan Failure – Damage to the liver, kidneys, and heart.
• Lung Fibrosis – Permanent lung scarring leading to long-term breathing problems.
• Post-SARS Fatigue Syndrome – Long-term weakness and difficulty breathing.

Prevention

• Public Health Measures:
  • Quarantine & contact tracing to stop virus spread.
  • Travel restrictions (screening passengers at airports).
  • Closing public places during outbreaks (e.g., schools, markets).
• Personal Protection:
  • Frequent handwashing with soap and water.
  • Wearing face masks in high-risk areas.
  • Avoiding close contact with sick individuals.
• Vaccine Development:
  • No approved vaccine for SARS, but research was ongoing.
  • SARS vaccines were being tested but were never mass-produced.