The biology of coronavirus

1. BIOLOGY OF CORONAVIRUS
Prof Nyasha Chin’ombe PhD (UCT)
Department of Medical Microbiology
College of Health Sciences
University of Zimbabwe
Seminar: 11 March 2020, 1200-1300hrs
Main Lecture Theatre

2. Main viral causes of respiratory
infections including common cold
are:
1. Rhinovirus
2. Coronavirus (CoV)
3. Adenovirus
4. Influenza virus,
5. Parainfluenza virus
6. Respiratory syncytial virus
7. Metapneumovirus
8. Bocavirus
Introduction

3. Introduction
• CoVs (Coronaviruses) - the second most
prevalent cause of the COMMON COLD (10-
15% - sometimes up to 35%)
• Infect humans & many different species eg cattle,
horses, camels, rodents, cats, dogs, bats, palm
civets, rabbits, snakes, several wild animals, birds
• Normally single strain of virus infects one species.
Some are able to infect more than one related
species.
• Rarely, CoVs from other species can infect people
& then spread between people as with SARS-
CoV, MERS-CoV & SARS-CoV-2.

4. History of CoVs
• CoVs first isolated in chicken in 1937 –
causing avian infectious bronchitis (IBV)
• First human CoVs were isolated in the
1960s
7 human CoVs
SARS CoV-2

5. • Common human CoVs
1. 229E (alpha coronavirus)
2. NL63 (alpha coronavirus)
3. OC43 (beta coronavirus)
4. HKU1 (beta coronavirus)
• Other human CoVs (novel)
5. SARS-CoV (beta coronavirus -
causes severe acute respiratory
syndrome, SARS)
6. MERS-CoV (beta coronavirus -
causes Middle East Respiratory
Syndrome, or MERS)
7. SARS-CoV-2 (beta coronavirus -
causes coronavirus disease
2019 - COVID-19)
•Globally, humans
get infected by these
4 which cause mild
respiratory infections
such as common
cold
•Pandemic potential
•High mortality
•Worldwide spread
•Immune naive
population

6. Classification of CoVs
MERS-CoV SARS-CoV-2SARS-CoV
229E NL63
HKU1
OC43

7. Epidemiology of CoVs
• Common cold due to coronaviruses occurs
in the colder months of winter & early
spring with sizable outbreaks every 2-4
years.
• Most people have been infected in their
lives by CoVs
• Reinfections are quite common (immunity
short-lived)

8. • The virus is most likely spread by aerosols and
in large droplets (e.g., sneezes).
• Route: Respiratory discharges, Stools
•
Transmission of CoVs

9. Transmission of CoVs
Zoonotic transmission followed by human-to-
human transmission

10. “Zoonotic transmission of some CoVs –
followed by human-to-human
transmission
Transmission of CoVs

11. Potential zoonotic transmission routes for SARS-CoV-2
Transmission of CoVs

12. All viruses initially existed in bats as CoV‐related viruses (SARSr‐CoV,
MERSr‐CoV, and SARSr‐CoV‐2) before acquiring mutations and
adapting to intermediate hosts and ultimately humans.
Origin and evolution of (A) SARS‐CoV, (B) MERS‐CoV,
and (C) SARS‐CoV‐2 in different hosts
pangolins, rats,
snakes?

13. Transmission of CoVs
CIVET CAT
Delicacy in Southern China

14. A crown-like appearance when
viewed by EM
Structure of CoVs

15. • Size: 80~160nm
• Enveloped viruses
• Helical nucleocapsids.
• Sensitive to acid, drying, heating to 56ºC.
• Viral genome structure:
 Single –stranded linear non segmented +ve
sense RNA
 27-31 kb, the largest among RNA viruses
 Genome contains 6 ORFs which encode
several viral proteins
•
Structure of CoVs

16. • S - Spike protein: receptor
binding, cell fusion, major
antigen
• E - Envelope protein: small,
envelope-associated protein
• M - Membrane protein:
transmembrane - budding &
envelope formation:
• HE - Haemagglutinin-esterase-
binding & cleavage activities
•N- Nucleoprotein – associated
with genome
Structure of CoVs
•Virus neutralizing antibodies - directed at the surface
glycoproteins
•Cellular immune responses are directed toward the S and
N proteins
The structural proteins of the CoVs

17. •Pathogenesis of CoVs
Replication occurs in the cytoplasm (an advantage)
Viral entry and replication

18. • CoVs primarily infect the upper
respiratory & sometimes
gastrointestinal and lower respiratory
tracts
• Symptoms range from mild self-
limiting diseases such as the
common cold to more severe forms
such as pneumonia.
• The novel CoVs - cause both
upper and lower respiratory
tract infections and can also
cause gastroenteritis.
Clinical syndromes associated with CoV infection

19. Clinical syndromes associated with CoV infection
SARS-CoV and MERS-CoV

20. Clinical syndromes associated with CoV infection
SARS-CoV-2
-causes acute, highly lethal pneumonia with clinical
symptoms similar to those reported for SARS-CoV &
MERS-CoV

21. • Specimen: Nasopharyngeal swabs or aspirates, throat
swabs or stool specimens. Serum is used for antibody
detection.
• Serological Testing
– Antigen detection in cells of respiratory secretions by IF
or ELISA
• Culture: 229E, OC43, SARS-CoV (Vero E6 cell), but
difficult
• Molecular Testing
– Viral RNA detection in by RT-PCR – golden standard
•
Laboratory Diagnosis of CoVs

22. • Specific treatment
– There is no specific treatment/drugs for CoVs.
– Treatment is symptomatic and supportive.
• Prevention
– No vaccine available – under development
– Infection Control and Prevention measures.
Treatment & prevention of CoVs

23. Thank you
for your
attention