Lec 18- disease ecology Flashcards
3 ways to look at simple dynamics of population?
- time series
- population of change
- per capita rate of change
what is time series?
number of individuals (N) at each time t
what is population rate of change?
added individuals per time step vs. population size (N); population grows with increase N
does per capita rate change with N?
no
when would slope decrease linearly (dN/dt/N vs. Population size size)
resources become limiting
with increasing N, so per capita
growth inevitably declines
Carrying capacity K:
the number of individuals of a particular
species that the local environment can support
why talk about disease?
Disease can alter individual fitness
and impact population dynamics.
disease
An “atypical” condition in a living
organism that causes some sort of
physiological impairment.
Can be caused by a variety of factors:
genetic abnormalities, exposure to
toxins, and interactions with organisms
- all disease-causing organisms are exploitative/selfish (donor + fitness)
infectious diseases:
caused by
organisms (e.g., viruses, bacteria,
fungi, etc.)
disease-causing parasite is restricted to?
protozoans*, helminths (parasitic worms)**, and
ectoparasites
covid-19 causes what health issues
severe acute respiratory syndrome (sARS coronavirus 2)
disease transmission
- direct: by physically touching an infected individual
- indirect: by touching a surface that physically touched an infected individual (inanimate contaminated object), animal vectors (ticks, fleas)
horizontal transmission
- among individuals of the same generation
- ex. influenza
- can be direct or indirect, usually no genetic basis
vertical transmission
from parent to offspring
is influenza horizontal or vertical transmission?
horizonal
3 steps to how viruses replicate in living cells
1.Virus bindsto and enters cells,then
2.deliversits genome to a site where it can
produce new copies of viral proteins and RNA
3.Viral proteins and RNA assemble into
new viral particles, and exit the host cell;
via the cell wall bursting (or‘lysing’)
both vertical and horizontally transmitted diseases
HIV, chicken pox, microcephaly and ZIKA
is covid horizontal or vertical?
Mostly horizontally transmitted (respiratory droplets, aerosols), vertical
transmission is rare
endemic
constant presence but
relatively low spread;
e.g., malaria in African
regions, possibly HIV
epidemic
sudden increase (high spread)
in certain regions;
e.g., Lyme disease,
early COVID spread
pandemic
global epidemic;
e.g., swine flu (2009),
COVID-19
disease fitness eq
𝑅0 =𝛽 𝑁 / (𝜈 + 𝑑 + 𝑟)
𝑅0
Basic reproduction number
average # of susceptible people that will be infected by a person with a disease in a native population w/o transmission interventions
𝛽
transmission rate (probability of infection)
