# Lethality vs. mortality rate

Currently, we are increasingly encountering the terms **lethality** and **mortality**; however, since these two terms do not have the same meaning, we will specifically address the difference here:

**The lethality rate** indicates what percentage of patients who get a certain disease also die from it. In the winter of 2017/2018, for example, there were around 120 deaths related to seasonal flu (influenza) every week in Luxembourg. If our fellow citizens had been tested for the virus back then, as is the case today in connection with the Coronavirus, this lethality rate could be calculated. But since these tests were not carried out, the most that can be communicated is the mortality rate.

**The mortality rate**, however, has a completely different meaning: it indicates how many people of a population group TOTALLY die in a certain period of time. Depending on what insight one wants to draw from the statistics, one can define the world population, the national population or only a specific group. Thus, for the flu that took so many lives here in Luxembourg in 2017/2018, one can only calculate the mortality rate associated with the influenza virus: what was the probability of dying from flu as a Luxembourger in this particularly tough flu season.

With the Coronavirus, on the other hand, we have the unique opportunity to publish a lethality rate because of the extreme testing strategy. For example, if we take the figures from December 11, 2020, we get a **lethality rate** of 0.96% for the year that has passed, with 392 deaths for every 40 755 "infected" people.

**The lethality rate** is, of course, always higher than **the mortality rate**, since it refers specifically to a smaller group (the infected). If we now put those who died of Corona in relation to the total population of 626 000 people, the mortality rate associated with Covid-19 is 392 / 626 000 = 0.0626%.

Mortality rates (all diseases, accidents... etc combined) in Luxembourg since 2017:

- 2017: 4 263 out of 590,667 = 0.72%
- 2018: 4 318 out of 602,000 = 0.71%
- 2019: 4 283 out of 614,000 = 0.69%
- 2020 (until October 31, 2020): 3 601 out of 626 108 = 0.57%

And for those interested in longer periods:

- 2000: 3 749/433 600 = 0.86%
- 2010: 3 760/502 066 = 0.75%