BIO220 Lecture 8 Flashcards
Virulence
Virulence
Extent of harm an infection causes on you
(highly virulent = death)
Additional mortality rate that a pathogen imposed on the host.
Impacts of the 1918 WWI influenza epidemic
Killed many people (highly virulent), then vanished
What causes Ebola haemorrhagic fever?
Ebola virus
Ebola virus causes…
Ebola haemorrhagic fever
Ebola haemorrhagic fever
sever, fatal disease
How is Ebola virus spread?
Air, contact
Symptoms of Ebola haemorrhagic fever
- High fever
- Headache
- Stomach & chest pain
- Vomiting
- Severe internal bleeding
Where did the first Ebola outbreak happen?
Zaire & Sudan
Where was the second time Ebola had an outbreak?
In monkeys that were imported into Virginia, USA
Where was the last time Ebola had an outbreak?
Africa (5 diff locations)
What is the “conventional wisdom” argument?
Pathogens and host will reach mutualistic association over time
- Pathogen that have high virulence will kill host (and self)
- High virulence pathogens are once that have recently invaded humans
Is the conventional wisdom correct in regards to virulence?
No
How do humans come in contact with the Ebola virus?
Bats -> ape, chimp -> humans
Do humans spread Ebola virus?
No, kills host too quickly
SARS
Severe Acute Respiratory Syndrome
SARS virus was so virulent because…
Most likely virus from another species that infected humans. Humans have no immunity at all.
What type of virus was responsible for SARS?
coronavirus: single stranded RNA virus.
Mixture of bird and other mammal viruses.
Coronaviruses typically cause
Mild-moderate upper respiratory illnesses in humans
What was the mortality rate for SARS?
5-10%
What virus was used to kill rabbits?
Myxoma virus
Why was the myxoma virus introduced?
Rabbit population exploded in Australia (brought from Europe)
What happened to the virulence of myxoma virus?
Went down (co-evolution between host and pathogen), but NOT TO ZERO. The virus still killed rabbits.
Level of virulence is caused by…
parasite replication rate in host
Parasite adaptation hypothesis
Level of virulence = parasite replication rate.
Want to maximize replication rate to spread more.