The figures in the next two tables come from different sources and are slightly out of synch with each other.
| Disease | Case Fatality Rate |
|---|---|
| Rabies | ~ 99% |
| Ebola | 83 - 90% |
| Plague, bubonic | 5 - 60% |
| Plague, pneumonic | 50% |
| Middle Eastern Respiratory Syndrome (MERS) | 45% |
| Plague, septicemic | 30 - 50% |
| Novel coronavirus (SARS-Cov-2) | 0.00% |
| Severe acute respiratory syndrome (SARS) | 11% |
| Spanish (1918) flu | > 2.5% |
| Disease | Year | Cases | Deaths |
|---|---|---|---|
| Novel coronavirus (SARS-Cov-2) | 2019 - present | 200,877,151 | 4,267,299 |
| Severe acute respiratory syndrome (SARS) | 2002 - 2003 | 8,098 | 774 |
| Middle East respiratory syndrome-related coronavirus (MERS-CoV) | 2012 - 2015 | >2,000 | >600 |
| H5N9 | 2013 - 2017 | 1,622 | 619 |
| H5N1 | 2003 - 2014 | 701 | 407 |
R0 is a measure of how many other people each patient infects. For example, with an R0 of 10, each person that
catches the disease will infect 10 others (on average).
For example:
| Generation | New people infected |
|---|---|
| 1 | 1 |
| 2 | 10 |
| 3 | 100 |
| 4 | 1000 |
As you can see, the numbers can ramp up very quickly.
The latest estimates for R0 for Covid-19 are between 4.7 and 6.6, and possibly up to as high as 11.3.
| Disease | R0 | Notes |
|---|---|---|
| Novel coronavirus (SARS-Cov-2) | 4.7 — 6.6 CI: 2.8 — 11.3 | Source (11 February 2020) |
| Novel coronavirus (SARS-Cov-2) | 2.2 (95% CI, 1.4 — 3.9) | Source (29 January 2020) |
| Novel coronavirus (SARS-Cov-2) | 2.2 (90% HDI: 1.4 — 3.8) | Source (24 January 2020) |
| Severe acute respiratory syndrome (SARS) | 2 — 5 | Airborne droplet |
| Spanish (1918) flu | 2 — 3 | Airborne droplet |
| Middle East respiratory syndrome-related coronavirus (MERS-CoV) | 0.3 — 0.8 | Airborne droplet |
The following graph shows the effect of different values of R0, namely 1.5, 2, 3, 4, 5, 6.
Each line stops at the generation at which it is still below world population, which is just under 8 billion people.
The line for R0=1.5 does not get high
enough to be visible, given the Y-axis scale, and the limit of 33 generations.
The real question is "how long is one generation?" There are estimates that people become infective within 12 to 24 hours of becoming being infected. This puts the length of one generation at 1 day, but this does not appear to be correct, unless the drastic lockdowns in China are distorting the R0 figures. Also, as more people become infected, the available population in a given area able to be infected drops off dramatically, slowing the R0.
So the chart below assumes "everyone in the world all together in one room, and people moving around constantly so that those who are infected can find new people to infect," which is not how the world actually is.
So view the chart as showing "worst possible case" of spread potential.
| R0 | Generation > world population |
|---|---|
| 2 | 34 |
| 3 | 22 |
| 4 | 18 |
| 5 | 16 |
| 6 | 14 |