# CDC Level 4 Travel Alert -- Doing the Math

• veithmoore

#### veithmoore

The 4 level system categorizes international destinations at a level four the 28 day infection rate per 100,000 > 500.
The population of Costa Rica is 5,094,000.
The WHO had 5,488 infections for 2/11/2022.
How would you calculate the infection rate per 100,000?
5,094,000 ÷ 100,000 = 51
5,488 ÷ 51= 108 cases, well below the 500 case threshold for a level four.
Of note, the highest infection number I saw in the last 28 days was 17,000, which is 333 per 100,000, still < 500.
Thanks!
The 4 level system categorizes international destinations at a level four if the 28 day infection rate per 100,000 > 500.

The population of Costa Rica is 5,094,000.

veithmoore said:
How would you calculate the infection rate per 100,000?
I would use similar fractions. That may be what you did, but for me it's more intuitive to see the similar fractions visually first:
$$\frac{5488}{5094000} = \frac{x}{100000}$$
Then just cross-multiply and solve for ##x##

veithmoore