Evolution Disease 2 Flashcards
Virulence
- harm a disease causes to a host
- general garm to a hosts health
- biology of transmission constrains virulence
How humans diseases arise
- pathogen can coevolve in parallel with host species
- Zoonotic originate in other species
SARS CoV-2
related to SARS, closest known relative in a coronavirus that circulates in bats
Herd Imnmunity
important for protecyting peoplr who cant get vaccinated. People with cancer or other life threatening diseases
- breakdown of herd immunity cn lead to disease outbreaks
Evolution of virulence
The evolution of virulence depends largely on transmission
Do pathogens have heritable variation in a trait
the viral load is heritable
viruses exhibit enormous heritable variation in their viral loads.
Does the traiyt influence the number of new infections
predicted number of new infections
= infectiousness, B, x duration, D
Virulence
harm inflicted b y pathogens, this is sometimes a by product of the reproduction and survival of the pathogen within the host
Other pathogens such as Salmonella, Cholera, E coli cause diarrhea
Transmission
very sick people are less mobile, reduced the likelihood of transmission
hosts who are not incapacitated provide more effective means of transmissio.
Virulence
- Stronger selection for competition within hosts favors rapid replication and increased virulence
- Stronger selection for movement between hosts reduced virulence
- high virulence will evolve in conditions with higher transmission
- Low virulence will evolve in conditions with lower transmission
Waterborne pathogens
tend to have less dependence of host for transmission, so they often are highly virulent
The voirulence of baterial pathogen also influences teh evolution of antibiotic resistance
higher virulence: more people taking antibiotics ____more antibotoic resistance
Vector borne pathogens
tend to have less dependence on mobility of host for transmission, so they often are highly virulent
- reduce transmission, reduce risk of exposure, favor the evolution of less virulent strains and kill mosquitos