Covid by Numbers

Question 1

what does it mean for bacterial growth data if a straight line can be plotted on a log scale?

Answer 1

it means that there is exponential growth

Question 2

what is the equation for the discrete growth of bacteria?

Answer 2

N(g) = N0 x 2^g

where:

N(g): number at generation g

N0: starting generation number

2^g: base 2 raised to power g. 2 is used as the base because bacteria divides into two

g: generation number

Question 3

what is the equation linking population size and generation g, reproduction number, generation number and starting population size?

Answer 3

Ng = R^g x N0

where:
- Ng is population size at generation g

- R is reproduction number

- g is generation number

- N0 is starting population size

Question 4

when does exponential growth occur?

Answer 4

when rate of growth is proportional to population size

Question 5

what is all the same in exponential growth for bacteria?

Answer 5

the doubling time

Question 6

when does exponential decay occur?

Answer 6

when the rate of decrease is proportional to population size

Question 7

what is R0

Answer 7

• the basic reproduction number

Question 8

what are 3 features of the basic reproduction number

Answer 8

• expected number of cases directly generated by one case
• all individuals are susceptible to infection
• no deliberate intervention in disease transmission

Question 9

what is R in infectious disease

Answer 9

the effective reproduction number

Question 10

what 4 things does R (in infectious disease) depend on

Answer 10

• opportunities for transmission (contact)
• duration of infectiousness
• transmission probability during each opportunity
• susceptibility ( for people who are not immune )

Question 11

why are more transmissible pathogens cause a much larger death toll than more lethal pathogens?

Answer 11

because although more lethal strains cause more deaths initially, more transmissble strains quickly outpace the lethal strains due to exponential growth in number of infections