microbial growth on a graph and CFR

Question 1

Lag Phase

Answer 1

Flat line on the graph.

Question 2

Log Phase (Exponential Phase)

Answer 2

Straight upward slope (linear in log scale).

Question 3

Stationary Phase

Answer 3

Plateau on the graph

Question 4

Death Phase

Answer 4

Downward slope (on log scale).

Question 5

Specific Growth Rate (μ)

Answer 5

μ = (ln N₂ − ln N₁) / (t₂ − t₁)

N₁ and N₂ = cell numbers at time t₁ and t₂ (during exponential phase)

Units: h⁻¹ (or min⁻¹)

Question 6

Doubling Time (td)

Answer 6

td = ln(2) / μ

Time it takes for population to double.

Question 7

Cumulative Case Fatality Ratio (%CFR):

Answer 7

%CFR=( Cumulativeconfirmedcases
/Cumulativedeaths)×10

Question 8

Corrected %CFR Formula:

Answer 8

%CorrectedCFR=(Cumulativeconfirmedcasesatday(t−10)/
Cumulativedeathsatdayt )×100

Identify the number of cumulative deaths as of today (day t).

Get the number of cumulative confirmed cases from 10 days ago (day t - 10).

Use the corrected CFR formula shown above.

Plug in the numbers to calculate the corrected %CFR.

Question 9

estimate the basic reproduction number, R

Answer 9

R=e ^r⋅T
r = exponential growth rate of the outbreak

T = serial interval (here, 15 days)

e = Euler’s number (~2.718)

r= ln(C t)- ln(c0)/ t

C₀ = number of cases at start

Cₜ = number of cases at end

t = time in days (e.g., 90 days for 3 months)
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