1. Coronaviruses are spherical or irregularly shaped viruses 80-220 nm in diameter that have club-shaped peplomers giving them a crown-like appearance. They contain a single-stranded RNA genome and envelope with three glycoproteins including the spike protein. 2. Severe Acute Respiratory Syndrome (SARS) is caused by a coronavirus called SARS-CoV. It emerged in China in 2002 and causes fever, respiratory symptoms, and can lead to respiratory distress and death in some cases. 3. SARS-CoV-2 is the coronavirus that causes Coronavirus Disease 2019 (COVID-19) which was declared

1. Coronaviruses
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Virology -PC_II 1

2. Properties
 Spherical/ irregularly-shaped
 80-220 nm diameter
 Envelope bearing distinctive, 'club-shaped' peplomers- 'crown-like' appearance
- three glycoproteins:
 S - Spike protein: receptor binding, cell fusion, major antigen
M - Membrane protein: transmembrane - budding & envelope formation
 HE – Hemagglutinin: hemagglutination, acetylesterase activity
 ss RNA (20-30kb), linear, non segmented, positive sense
- the largest genome among RNA viruses
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Virology -PC_II

3. Coronavirus
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Virology -PC_II

4. Pathogenesis
 Highly species-specific
 Little is known
 Display a tropism for epithelial cells of the respiratory or gastrointestinal tract
 Remain limited to the upper respiratory tract
- a slow , patchy destruction of ciliated epithelial cells and the loss of beating cilia
 disease development
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Virology -PC_II

5. Clinical findings
 Respiratory infections (common), including Severe Acute
Respiratory Syndrome (SARS)
 Enteric infections (occasionally) - mostly in infants <12
months)
 Neurological syndromes (rare)
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Virology -PC_II

6. Severe Acute Respiratory Syndrome
 Apparently new respiratory disease emerged in China November 2002
 Progresses to a global health threat by sparing of 2003
 Cases reported China, Hong Kong, Vietnam, Singapore and
Canada
 March 15,2003 WHO issued global travel alert
 Potential pandemic ?
 Casual agent ?
 No diagnostic laboratory assays, no defined properties or risk
factors for transmission, no infection control practices, no
known treatment or preventive measures
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Virology -PC_II

7. SARS- Clinical manifestations
- fever above 38 degrees
- headache and general malaise
- Shortness of breath →hypoxia
- respiratory symptoms are initially usually mild but after a few days (or a
week), the patient may develop a dry non-productive cough and breathing may
become difficult (dyspnea).
• Respiratory distress leads to death in 3-30% of cases.
Laboratory tests show a reduction in lymphocyte numbers and a rise in
aminotransferase activity which indicates damage to the liver.
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Virology -PC_II

8. SARS Coronavirus (SARS CoV)
 Coronaviruses
 High degree of mutation (antigenic drift)
 High frequency of recombination (antigenic shift)
- Evolution of new viruses /strains
- (SARS CoV) may be hybrid of mammalian and avian coronaviruses
- replicate protein was of mammalian origin
- the matrix and nucleocapsid proteins of avian origin
- the host determining spike protein was of a mammalian-avian
mosaic origin
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Virology -PC_II

9. SARS- Diagnosis
 CDC recommendations
• chest radiograph
• pulse oximetry
• blood cultures
• sputum Gram's stain and culture, and
• testing for viral respiratory pathogens, notably influenza A and B and respiratory
syncytial virus.
• A specimen for Legionella and pneumococcal
• urinary antigen testing should also be considered.
 People with suspected SARS should be isolated and quarantined.
 SARS- Diagnosis – specific
• ELISA to detect SARS-CoV antibodies
• Nucleic acid assays to detect SARS-CoV
• RT-PCR to detect SARS-CoV infection
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Virology -PC_II

10. SARS - Treatment
 No agreed treatment for SARS
 Management of symptoms.
 no vaccine against the SARS virus or any other human Coronavirus.
 A major problem with live virus vaccine is antigenic shift and unpredictable
outcomes
 Possibility remains that SARS may reemerge from unidentified animal
reservoirs or from persistently infected humans
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Virology -PC_II

11. SARS-CoV-2 (COVID-19)
 Coronavirus disease 2019 (COVID-19) is an infectious respiratory
tract infection caused by SARS-CoV-2
 On 30 January 2020 WHO declared COVID-19 a public health
emergency of international concern
 On 11 March declared it as a global pandemic

12. Virology-Structure and Genome of SARS-CoV-2
 Single-stranded RNA viruses
 Enveloped positive sense
 SARS CoV-2 contains four structural
proteins

13. Transmission, pathogenesis, replication of SARS-CoV-2 (COVID-19)
• Modes of transmission
 Droplets transmission
 Contact transmission
 Aerosol transmission….????

14. Pathogenesis
of
SARS-CoV-2
(COVID-19)

15. Replication of Coronavirus (SARS-CoV-2)

16. Signs and Symptoms of COVID-19
 The incubation period, the duration from the exposure to the virus
to the onset of symptoms ranges from 1-14 days (average 5 days).
 The virus is most contagious for the first three days after the
appearance of symptoms.

18. Risk factors of COVID-19
 The primary risk factor associated with coronavirus is age.
 A case fatality rate of 0.32% is seen in those aged below 60 years
 6.4% in those aged ≥60 years
 as high as 13.4% in those aged more than 80 years.
 Underlying disorders
 hypertension, chronic obstructive pulmonary disease, diabetes,
cardiovascular disease),
 are found to be at more risk of developing severe symptoms.

21. Reading assignments on
• Rota virus