Case 6 - Introduction to Virology Flashcards
(23 cards)
What is an infection?
An infection is when one organism (1 exception) colonises another organism.
These can be:
Prion (The exception)
Viruses (can also be debated!)
Bacteria
Fungi
Parasites (uni-cellular or multi-cellular)
Are transmissible.
what is miasma?
Polluted air.
Thought to account for infectious disease.
Widely held theory in western and easter medicine
miasma influenced European medical science for thousands of years
what’s germ theory
Germs (any micro-organism) cause disease in humans and can spread (contagious).
Manner in which they spread is different for different organisms.
Theory is quite well-established and it’s proven (not really a theory then)
What about Viruses?
Much smaller than bacteria.
Only possible to visualise with electron-microscope.
What’s an RNA virus?
Viral genome made using RNA instead of DNA.
RNA viruses have high mutation rate.
Why is this significant?
As viruses mutate → lots of changes and are unpredictable, e.g can make virus more susceptible to immune system
RNA viruses can have their genome orientated in different ways:
Positive sense.
Negative sense.
dsRNA
what is Influenza
Influenza is a viral infection caused by viruses belonging to the Orthomyxoviridae family.
[The viral family consists of RNA viruses.
This is clinically important]
3 genera of the Orthomyxoviridae are known to infect humans, which are:
Influenza A
Influenza B
Influenza C
Flu has two very important structural proteins:
Haemagglutinin -18 subtypes found in the wild.
Neuraminidase - 9 subtypes found in the wild. Enzyme which cuts sialic acid from viral particles.
Flu has two very important structural proteins. These proteins also allow for a system of categorisation to be used (primarily for Influenzae A)
H1N1
H5N1
The flu virus has two main mechanisms of evolution, which are
Antigenic drift.
Antigenic shift
Antigenic shift is caused by?
Antigenic shift is caused by exchange of genetic information between viruses.
Allows for mixing between avian, swine and human flu.
Antigenic drift is caused by?
Antigenic drift is caused by accumulation of genetic mutations.
what about Smallpox?
Caused by the Variola virus.
[responsible for lots of deaths in 20th century]
No known cure until a vaccine came in 1796
Evolution of variola.
Believed to have evolved from an animal virus.
Pox virus family has 4 viruses which can infect humans:
Variola, Vaccinia, Mpox and Cowpox.
used to be endemic in Africa ages back
Social aspect of disease.
Social aspect of disease can be as significant as physical aspects.
Feelings of the affected person:
Depression
Anxiety
Feelings of society at large:
Sufferers are unclean
Morally depraved
Burden
Social aspect is not always fixed in time/location.
Obesity.
How do vaccinations work?
The body has three main defences against infection, which are:
Passive barriers.
Innate Immune System.
Adaptive Immune System.
Vaccinations prime the adaptive immune system.
Lymphocytes.
Antibodies.
Body will remember the exposure.
Why are viruses so difficult to treat?
Viral infections are often incredibly acute.
- No time for drugs to work!
Virions rely exclusively on hijacked cellular processes.
- Difficult to target drugs.
- No metabolism.
It is possible to target some viral processes using?
Anti-retroviral drugs
Inhibitors of neuraminidase are “useful” in management of ___1___. An example of this is __2__. It helps prevent new viruses escape their ___3__ cells
1 - influenza
2 - Tamiflu (Oseltamivir)
3 - incubator
Does Oseltamivir actually work?
Very mixed bag of evidence.
Some nasty side effects.
Resistance rates can be as high as 3%
National and international level responses are required to manage and prevent viral disease. These responses have multiple strands:
Prevent spread.
Ensure treatment.
Prevent reoccurrence.
Discover new threats
