Lecture 9 Flashcards
What was the timeline of the SARS outbreak in 2002-2003?
Nov 16, 2002: SARS first breakout in Guang Dong
January 31 2003: 1st super spreader admitted to hospital in Guangzhou
Feb 2003: Dr. Liu become sick, patient zero at hotel, infecting 23 others in hotel
Feb 23, 2003: Kwan Sui-Chu returned to Toronto from Hong Kong, spread virus to Grace Hospital and other Hospitals
February 26, 2003: J. Chen became ill on flight to Singapore, stopped in Hanoi, infected 38 hospital staff
Canada: 438 probable cases, 44 deaths
How did SARS put Coronoaviridae on the world map?
July 2003: reached 37 countries via air travel, and confirmed cases: 8,098, and the fatalities were 774
20% of infections occurred in ICU and hospitals
Transmission required close contact
Isolation and quarantine were enacted
Schools closed
High-rank government officials fired
Fear and panic!
What is the morphology and capsid structure?
Glycoprotein Spikes (S) gives virion a ‘crown’ appearance, hence the name Coronavirus
Spherical, with an envelope, 120-160 nm in diameter
Several surface glycoproteins, student on viral envelope: S, M, E, and HE (for some viruses)
Coiled, so can package within virion, helical nucleocapsid and a gigantic RNA genome
+ssRNA genome: 27.6 - 31 kb
Slightly bigger than influenza
What are some of the cornoviridae diseases?
Respiratory infections in humans:
30% of the “common cold” –> rhinovirus causes most
Rare infections of the lower respiratory tract: pneumonia, death
Severe acute respiratory syndrome (SARS-CoV): 2002- 2003 (Southern China)
Middle East respiratory syndrome (MERS- CoV): 2012 (Saudi Arabia) –> Not very transmissible
COVID19 (SARS-COV2): 2019 (Wuhan)
Which animals serve as natural reservoirs for coronaviruses?
Primary hosts: bats
Intermediary: Civets, racoon dogs, pangolin, giraffe, cheetah, whale, birds
What are some coronaviruses that cause infections in animals?
Respiratory tract: Avian infectious bronchitis
GI tract: Porcine transmissible gastroenteritis
Liver: Murine hepatitis
CNS: Murine hepatitis and others
Explain IBV
First reported in 1930s in US
Major viral disease that threats the global poultry industry
Chickens of all ages are susceptible; but young chickens are more severely infected
Incubation period: 18- 36 hours
Highly contagious; infections spread throughout an entire flock in 1-2 days
Weight loss, drop in egg production or loss of the ability to lay eggs (false layers)
Billions of chickens succumb to IBV annually
Some IBV strains are nephron-pathogenic, causing damage to the kidney
What is the taxonomy of coronaviruses?
Order: Nidovirales
Family: Coronaviridae
Subfamily: Orthocoronavirinae
What genus is the SARS-CoV/SARS- CoV2 in?
Betacoronavirus genus
Explain the phylogenetics of the coronaviruses
Coronavirinae:
Betacoronavirus, Alphacoronavirus, and Gamma-Coronavirus
Possibly: Torovirinae:
Torovirus, Bafinivirus
What is the genome structure of coronaviruses?
Overall identify over genome: 54%
Coronaviruses contains viruses with the largest RNA genomes identified, 27 - 32 kb
5’ cap
3’ polyA tail
ORF1a and ORF1b account for three quarters of the viral genome
Encode two polyproteins:
Core structural proteins:
S, E, M,N plus numerous and variable accessary proteins
What is special about the replicase genes in Nidovirales?
Replicase genes occupy about 3 quarters of the viral genome
How are the replicase poly proteins processed in coronaviruses?
Two replicase poly proteins are processed into 16 proteins for genome replication and transcription
ORF1a and ORF1b encode all proteins required for genome replication and transcription
ORF1b is translated via a 1 ribosome frameshifiting mechanism, resulting in a large fusion protein, pp1ab
EXON protein: 3’ –> 5’ endonuclease activity
Ribbosomal frameshifting occurs only occasionally
