5/10/24 - Lecture 22: Diseases

Question 1

What are diseases caused by?

Answer 1

Micro- and macroparasites such as viruses, bacteria, worms, etc.

Question 2

How can diseases be transmitted?

Answer 2

They can be transmitted via casual contact, sexually, or a vector (ex: mosquito)

Question 3

R0

Answer 3

Average number of people infected by an individual during their infectious period in a mostly susceptible population

Question 4

What is R0 equal to?

Answer 4

R0 = pCD

D: Duration of infectious period in D days
C: Rate of contact of C individuals per day
p: Probability of transmission at contact

Question 5

Effective reproductive number R

Answer 5

Expected number of cases caused by a typical infectious individual in a population that need not be wholly susceptible.

Keeps decreasing over the course of the epidemic. At the peak, it is = 1 and R < 1 thereafter

Question 6

How to find R0, r, or t

Answer 6

R0 = e^rt
If you’re given one of these three variables (R0, r, or t), you can calculate the other

Question 7

How does vaccination affect R0? What is the significance of this?

Answer 7

It turns R0 to (1-v)R0.
v: proportion of population vaccinated
Then we just need (1-v)R0 < 1 to eradicate the disease

Question 8

Herd immunity

Answer 8

Only have to vaccinate a fraction of the population to eradicate a disease

Question 9

Why don’t hosts evolve to become completely resistant to a pathogen?

Answer 9

Because of tradeoffs. For example, the host may not be able to produce as many offspring.

Question 10

Why might a pathogen evolve to become less lethal?

Answer 10

Because of tradeoffs. For example, if it kills too many, then it won’t have any hosts to infect