Pandemic 2020 #3 – Terms to Know

There are a lot of terms thrown about when people discuss viruses and pandemics. It’s important to know what these are in order to better understand the data and information you’re exposed to. I’ll expand this list as needed, but the information we’ll be going over soon will contain these terms. 


Epidemic – Spread of an infectious disease within a localized community. 

Pandemic – Disease prevalent over the entire world. 

Mortality Rate or Death Rate – a measurement of deaths scaled to the total population. Often expressed in terms of number of deaths per 1,000 or per 1,000,000.

CFR – Case Fatality Rate – The number of deaths in relation to the total number diagnosed with the disease over a certain period of time. The CFR is only finalized when all of the cases have been resolved (recover or die).

Infection Fatality Rate – Closely related to the CFR, but tries to the estimates asymptomatic and undiagnosed cases. This can lead to a good deal of speculation, depending on the accuracies of the estimates.

RFR – Resolved Fatality Rate – The number of deaths in relation to the total number of resolved cases (deaths and recovered). As far as I can tell, this isn’t a formal statistic number and first heard about it on Peak Prosperity. One of the issues with interpreting this number is the different incubation periods each person has. 

Infection Rate (Rate of Infection) – Typically used to measure the frequency of occurrence of new cases within a defined population for a specified period of time. (Number of infections ÷ Population at Risk) x 100 (or some other constant). This works well when you have a small population, but it’s almost meaningless when looking at the entire US population.

Active Cases (Currently Infected Cases) – People who are still infected with the disease. These are cases that have not resolved yet.

Resolved Cases – People who have either recovered from the infection or have died from it. 

Recovered Cases – People who recovered and are no longer infected.

Serious Cases – Infected people who need hospital care.

Critical Cases – Infected people needed Intensive Care.

Herd Immunity – When most of a population is immune to an infection, the spread of it will be greatly reduced to those who aren’t (yet) immune. Depending on the how contagious the disease is, we don’t reach herd immunity until 70% to 90% of the population is immune. The spread of the disease will slow as more people become immune to it, so 60% population immunity is better then 30%, or 10%.

R0 (R Naught) – Basic Reproduction Number – A number of how contagious an infection is, by telling you the average number of people an infected person will infect. 

Three possibilities exist for the potential transmission or decline of a disease, depending on its R0 value:

  • If R0 is less than 1, each existing infection causes less than one new infection. In this case, the disease will decline and eventually die out.
  • If R0 equals 1, each existing infection causes one new infection. The disease will stay alive and stable, but there won’t be an outbreak or an epidemic.
  • If R0 is more than 1, each existing infection causes more than one new infection. The disease will be transmitted between people, and there may be an outbreak or epidemic.
  • (source:


Community Spread – An infection that is spreading randomly in the community. 

Isolation – Mitigation taken to protect the patient. 

Reverse Isolation – Mitigation to protect you from infection.

N95/100 Rating – Respirators come with a Letter and Number rating:

N – Not resistant to oil

R – Resistant to oil

P – Oil proof

95 – Filters 95% of particles 0.3 microns and larger.

99 – Filters 99% of particles 0.3 microns and larger.

100 – Filters 99.97% of particles 0.3 microns and larger.

There is an great page that spells this out and has some examples of particle sizes. I’d suggest saving this page:

Some interesting notes:

  • 1 micron = 1 micrometer
  • the flu is 0.17 microns.
  • the coronavirus is 0.125 microns

So, how can a 0.3 micron filter remove viruses less than half that size? Viruses rarely float in the air by themselves; they are usually stuck to something else: bacteria, moisture droplets, etc. The filter media in these masks are electrostatic and attract particles and trap them in the filter.

This entry was posted in Pandemic. Bookmark the permalink.

Join in on the discussion!