Microbiology 7-Evolution and emergence of new viruses Flashcards
What is zoonosis
Crossing of an animal pathogen into humans
What stops zoonosis
Host range barrier
What is the quasispecies
All the mutations of a single virus within a single person
Can be bottlenecked on transmisssion
Why do viruses change rapidly under new selection pressures
Replicate Fast
Replicate in Large Numbers
High Mutation Rate
Describe how HIV drug resistance is prevented
There are drugs which target different parts of the HIV life cycle
If you give the patient a protease inhibitor, a single nucleotide switch may make the protease inhibitor ineffective
So you must give a combination of antiviral drugs because in that case, for a virus to be resistant, it would need 5 or so simultaneous mutations which is unlikely.
Error rate is roughly 1 per 10,000 nucleotides and as each genome is roughly 10,000 nucleotides long, each HIV genome is likely to be slightly different
Therefore, monotherapy would almost certainly result in proliferation of a resistant population of HIV
What is antigenic drift
antigens gradually change over a period of time due to pressure exerted by antibodies
What makes vaccinating agaisnt rhinovirus so hard
don’t show antigenic drift but there are so many of them circulating at the same time so you are likely to catch many of them in your lifetime.
How do new viruses emerge (5)
Zoonosis
Genetic Variation
Increased Exposure - travel or world population
Increased Exposure - spread of vector
New Discoveries
Global influences of emerging infections (7)
Environmental modifications/demographics
World population
Climate change
Travel
Farming practices; monocultures
Immunosuppressed humans
Medical progress
What are arbovirus?
A class of viruses transmitted to humans by arthropods such as mosquitoes and ticks.
Describe the emergence of west nile virus in NYC
Belongs to Japanese encephalitis group of flaviviruses - cause disease by going to the brain
1999 - West Nile Virus was found in New York - bad year for mosquitoes in NY
Some elderly people succumbed to a brain disease - crows and birds at the zoo became ill
RT-PCR showed that the virus originated from Israel
Why is dengue worse the more times you get it
First time you get it isnt that bad
Second time you get infected by a different SEROTYPE the antibodies from the first time make you more sick
You get Dengue Haemorrhagic fever
What is the Antibody Dependent Enhancement of the Infection
If infected by a different viral serotype - the antibodies bind loosely to the antigens but don’t block it
Then the antibodies can bind to Fc receptors on immune cells thus carrying the virus into immune cells
This leads to a cytokine storm and dengue haemorrhagic fever
What is zika virus and why is the virus dangerous now
An arbovirus
Mutation- new tropism so gained neurovirulence
Interfering with expression of MCPH1
can cross the placenta to give children microcephaly
What is chikinguyna
arbovirus
Gives muscle and joint pains
