MICRO: ‘21st century pandemics: influenza and COVID’ Flashcards
What are three main features of pathogens causing a pandemic?
- will have novel antigenicity
- will replicate efficiently in human cells.
- will transmit efficiently between people
List 4 viruses with pandemic potential.
- Inflenza
- Coronavirus (SARS-COV2)
- Nipah - found in Bangladesh etc
- Insect borne:
- West Nile virus
- Dengue
- Zika
When have influenza viruses caused pandemics?
- 1918 - Spanish
- 1957
- 1968
- 2006 - Swine flu
World War I lasted 4 years from 1914 to 1918 and resulted in 16 million deaths worldwide. How many people died as a result of the 1918 influenza pandemic?
- 50,000
- 500,000
- 5 million
- 50 million
50 million
The natural reservoir of influenza A viruses is
- Pigs
- Chickens
- Ducks
- Tigers
Ducks - Aquatic birds are natural hosts to 16 antigenically distinct influenza A viruses
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What are the characteristics of
8 segmented
single stranded
DNA virus
Haemagglutin (HA) and Neuraminidase (NA)
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How must an avian influenza virus mutate to infect humans?
To jump from birds to humans an avian-origin influenza must mutate to:
- Replicate efficiently in the human airway.
- Transmit through the air between people (rather than water)
What is the spike protein in influenza called?
Haemagglutinin
How does an avian influenza gain the capacity to replicate in humans? What is the most common mutation?
- Virus enters and buds into the cytoplasm
- Enters nucelus
- ANP32 proteins in nucelus are essential host cofactors that support influenza polymerase activity
- For ANP32 to help it work the virus must adapt by a single amino acid change in PB2 E627K or PB2 627K (1918)
What further genetic changes are necessary for an avian influenza virus gain capacity to replicate in human cells?
- Reassortment –> antigenic shift (But this is not sufficient on its own )
- + Further HA mutations - must occur for it to replicate in the airway and be transmitted through air
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How does pH in the respiratory tract affect influenza entry?
Influenza entry is pH dependent and HA protein is pH sensitive
- pH is acidic in the URT - avian viruses cannot survive here and must mutate to do so
- pH is neutral in the LRT
Summarise the steps of adaptation of avian influenza viruses to humans.
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What measures are taken in a pandemic response?
- Non pharmaceutical interventions - face mask, isolation, distancing
- Antiviral drugs
- Vaccines
“Several antiviral drugs already exist for influenza, and are licensed for use in the clinic. However unlike HAART for HIV we don’t use them together.”
True or false:
True - we do not combine influenza drugs together as they are not licensed for this
What is the MOA of NA inhibitors?
NA (AKA sialidase - sialic acid enyzume) is important in budding out to infect a new cell
NAi acts by inhibiting NA so that the virus is tethered to the cell and does not leave
Examples are oseltamivir (Tamiflu) and zanamivir (Relenza)
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