Chapter 1: Foundations and Infections of a Susceptible Host

no

do viruses fit into the tree of life?

viruses

microscopic infectious agents that can reproduce only inside a cell that they infect; they are obligate parasites of their host cells

virions

infectious particles

genome and a protein code

what makes up a virus?

cannot reproduce on their own and they have no cell structure

what two characteristics of life are viruses missing?

true

T/F: virion and genome sizes across viruses vary

mRNA

what molecule must all viruses produce for reproduction?

100,000

how many virus particles are in a ml of blood?

true

T/F: viruses are host specific

large populations or continually contacting new populations

what conditions are necessary for the establishment of highly virulent viruses?

virulent

hard hitting viruses that make their hosts sick

retroviruses

what might some of the earliest human-adapted viruses be?

viruses that can insert their DNA into our genome

what are retroviruses?

disease in humans and pets, livestock disease, cancer, and economic/societal impacts

what are the harms of viruses?

zoonoses

disease that can be spread from animals to humans

food webs, interactions with other pathogens, conservation, our own genome, research, pharmaceuticals, and tracing human migration

benefits of viruses

that DNA is the molecule that carries genetic information

what did the hershey-chase experiment discover?

bacteriophage

viruses that infect bacteria

prophage

viral genetic material

lytic and lysogenic

what are the two reproductive cycles of viruses?

lytic cycle

genome is used to make new phage genomes; destuctive

lysogenic cycle

genome enters the bacterial host genome; less destructive

pathogen

organism or agent that causes disease

regularly associated with the disease and its characteristic lesions, isolated from the disease host and grown in culture, reproduced when culture is introduced into a healthy host, and reisolated from experimentally infected host

what are koch’s postulates?

won’t grow in a culture and the pathogen and symptoms might not align

which of koch’s postulates might not apply directly to viruses?

genome, symmetry of capsid, presence of envelope, and dimensions of capsid and virion

how are viruses classified?

nucleic acid sequencing

what is the most important way to classify viruses?

both

can DNA be single or double stranded?

+nucleic acid

nucleic acid in the same orientation as translatable mRNA

-nucleic acid

nucleic acid in the opposite orientation was translatable mRNA

packaged inside particles that mediate transmission and contains info for initiating and completing an infectious cycle

what are some general characteristics of the viral genome?

attachment and entry, decoding of genome, genome replication, and assembly and release

what are the stages of the infectious cycle?

animals were domesticated, human population drastically increased, cities developed, and worldwide travel became possible

what events happened within 10,000 years that led to historic viral outbreaks?

epidemic

localized outbreak

pandemic

global outbreak

pathogenesis

development of a disease

etiology

cause of disease

vector

carrier that transmits virus (or other infectious agent) from one host to another

endemic

a disease or condition typical of a particular population or geographic area; persisting in a population for a long period without reintroduction of the causative agent from outside sources

incidence

number of new cases diagnosed within a specific time period

prevalence

percentage of current infections at a given time within a population

morbidity

being harmed by a virus

mortality

killed by the virus

R0

the number of secondary infections that can arise in a large population of susceptible hosts from a single infected individual

>1

what R0 value would cause a virus to spread?

<1

what R0 value would cause the spread of a virus to die out?

reduce R0 value

how can we reduce the spread of a virus?

parents exposed to young children, immunity/vaccination status, and proximity to people or vulnerable populations

what are some reasons why R0 values might be different across infected people?

humidity

what is an abiotic factor that might influence the transmission of an airborne virus?

network theory

contact tracing can slow the spread of an infection by identifying individuals at risk of having contracted (and passing on) a pathogen