(Prepared by: Noopur, 20220901022)
How does population size affect viruses?
The spread of deadly virus can be enhanced with the increasing
number of human beings.
Population genetic diversity plays a prominent role in viral
evolution. This diversity is subsequently modulated by natural selection and
random genetics drift, whose action in turn depends on population size.
What happens if virus mutation take place due to
population size?
Virus mutations create genetic
diversity, which is subject to the opposing actions of selection and random
genetic drift, and this is affected by the size of the virus population. The genetic diversity can lead to
negative or positive virus-virus interaction. Size of viral population
determines the genetic drift, which in turn depends on spatial structure,
population size bottlenecks during host-to-host transmission. Therefore,
selection and drift are conditioned by population size.
The high mutation rate of viruses,
coupled with short generation times and large population sizes, allow viruses
to rapidly adapt to the host environment.
What is population size
bottlenecks?
Population bottlenecks leading to a
drastic reduction of the population size, which are common in the evolutionary
dynamics of natural populations; there occurrence is known to have implication
for virus evolution. It occurs when a population size is reduced for at least
one generation.
What if population size is large?
Or small?
When the population size is large, selection becomes predominant
and random genetic drift become less common. When the population size is small,
random effects may obscure the effects of selection. The population sizes of
RNA viruses are often very large, factors such as variation in replication
potential among variants, differences in generation time among infected cells
and population bottlenecks, might lead to an effective population size.
Despite virus enormous population sizes, viruses experience
significant genetic drift. This is because the strength of drift depends on the
effective population size, not on the census size.
Viral population genetic diversity plays a major role in ability
of viruses to cause disease. In general pathogens evolve faster than their
hosts owing to their shorter generation times and higher population size
One unique characteristic of viruses is their MOI, which is the
ratio between the number of viruses and the infecting cells. MOI can be subject
to the constantly changing size of the virus population.
The viral evolution creates huge population size within the
infected host. However, this huge population size is punctuated by frequent
bottlenecks.
References
[1] [1] A. Stern and R. Andino, “Viral Evolution: It is All About Mutations,” in Viral Pathogenesis: From Basics to Systems Biology: Third Edition, Elsevier Inc., 2016, pp. 233–240. doi: 10.1016/B978-0-12-800964-2.00017-3.
[2] [2] A. Moya, E. C. Holmes, and F. González-Candelas, “The
population genetics and evolutionary epidemiology of RNA viruses,” Nature
Reviews Microbiology, vol. 2, no. 4. pp. 279–288, Apr. 2004. doi:
10.1038/nrmicro863.
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