Week 3: Emerging viruses affecting respiratory system

Question 1

Transmission modes for SARS-CoV

Answer 1

• most likely in respiratory droplets, but also sweat, urine, feces
• droplets generated by a sneeze or cough contain large amount of viral particles and some are able to penetrate nucus and infect underlying epithelial cells

Question 2

Origin of SARS-CoV

Answer 2

• Coronavirus with positive sense ssRNA

- emerged from bat, then spread to civets and served as incubator for virus to evolve and spread to human

Question 3

Role of ACE2/spike protein in SARS-CoV cross species transmission

Answer 3

• spike protein plays vital role in viral entry, cell to cell spread, and determining tissue tropism
• genetic diversity in bat-derived sequences, especially in S gene that allows variants to cross species barrier

Question 4

Role of ACE2 in pathogenesis

Answer 4

• Angiotensin converting enzyme 2. resides on epithelium of the respiratory tract. spike protein S binds to ACE2
• the binding of ACE2 by S protein down regulates the ACE2 expressing (has protective role in lung)

Question 5

How does immune dysregulation contribute to pathogenesis of SARS?

Answer 5

• infection of immune cells disrupts normal cellular function. leads to lymphoenia and atrophy of lymphoid tissues
• pro inflammatory cytokines produced by viral infection in increased amounts for excessive amount of time
• autoimmunity: adaptive immune response might be directed against host epitopes

Question 6

Taxonomy of MERS-CoV

Answer 6

• belongs to genus betacoronavirua lineage C

- closest relatives are bat coronaviruses HKU4/5

Question 7

species of virus that caused the 2014 Ebola outbreak

Answer 7

• Filoviridae family. There are 4 species that infect humans. Zaire ebolavirus was the one responsible for outbreak
• negative strand, enveloped RNA virus

Question 8

pathogenesis of Ebola virus

Answer 8

• can infect most cells
• upon entering host, virus infects Dendritic cells, resulting in non responsiveness of T cells and reduced antibodies made thereafter
• virus is able to replicate very quickly
• tissue necrosis of parenchymal cells in many organs
• vascular injury/hemorrhage due to breakdown of endothelial cells by viral glycoprotein

Question 9

symptoms of Ebola hemorrhagic fever

Answer 9

• incubation period 2-21 days. disease onset is sudden
• flu-like symptoms: nausea, diarrhea, vomiting in few days, rash maybe
• Affects GI, respiratory, nervous system
• hemorrhage develops during peak of illness
• lab findings: low WBC, platelet counts, elevated liver enzymes

Question 10

why is 2014 Ebola outbreak at such a large scale

Question 11

SARS overview

Answer 11

• form of atypical pneumonia: high fever, chills, rigors, headache, dizziness, malaise, myalgia, cough, breathing difficulty
• outreak was 2002-2003 and then 2003-2004

Question 12

MERS-CoV

Answer 12

• reservoir is fruit bat
• camel is intermediate, patients contract from camel
• symptoms: fever, cough, dyspnea, GI symptoms, 1 or more chronic conditions: diabetes, HTN, heart disease, kidney disease