Evolution and emergence of new viruses Flashcards
(21 cards)
What is zoonosis?
Where viruses travels from animal reservoirs to humans
How does zoonosis occur?
Where viruses evolve to overcome host range barrier by adapting to different type of cell
What is a pandemic?
Epidemic of a worldwide scale - widespread infectious disease
What is a quasispecies?
Species that are related by similar mutation, competing with highly mutagenic environment
HOw do viruses become drug resistant?
High mutation rate
Large progeny number - replicate bare
Short replication time
What affects viral proliferation?
Relative fitness of wild type vs dug resistant virus in vivo.
How might antiviral drugs be tailored to both resistant and non-resistant viruses?
Multi-drug therapy for elimination of quasispecies - HIV HAART
HOw do viruses emerge and re-emerge?
Viruses undergo lot of mutations due to the mistake-prone replication cycle that is very fast
This means they evolve bare quick
So, the mutations that provide beenficail response are selected - advatnage
How do NEW viruses emerge
Zoonosis
Genetic variation
Increased exposure - spread and popu
New discoveries
What is antigenic drift?
Selection pressure causes ones that mutate preferably to survive, then outnumber the ones that havent mutated and spread - replacing it
- INFLUENZA
What is antigenic shift?
Reassortment of RNA regions that change the haemaglutinin or neuraminidase, leading to pathogenicity to humans
- H5N1 not normally pathogenic to humans but when above happens it is - H3N2 influenza
What are some global influences on emerging infections?
World popn
Climate change
travel
Medical progress
Immunosuppressed humans
What is an arbovirus? Give examples
Virus transmitted by mosquito or arthropod
- Yello fever
- Dengue
- Zika
- West Nile
What is a dead end host of WNV?
Human and horse as can’t pass virus on to other species
How did WNV re-emerge in New York?
Birds in Bronx Zoo - not sure what happened after maybe viraemic human or infected mosquito
How did Dengue emerge and re-emerge
Bite by aedes aegypti
Mosquito transfers from infected to ranodm - 50-100mill cases
What are the risk factors for DHF
Age
Pre-existing antibody why?
Higher risk in secondary ifnection and area with more than one serotype
How are antibodies helpful or not in dengue?
Helpful as neutralise - opsonin or prevent fusion wi endosome so no exocytosis
Not hekpful as enhance uptake or virion
Give examples of new human viruses that have emerged from animal sources
Ebola
Hendra
Nipah
How did SARS emerge and re-emerge
resp syndrome human transmission in China - 2003 - 8422 cases, 916 fatalitiy Infectious droplets Bats, raccoon dogs - ACE-2 protein
How did MERS emerge and re-emerge
Middle Eat - travellers , found in camels
