R0 or R0 is pronounced “R naught.” It’s a mathematical term that indicates how many people will be infected from a single person who has a disease.
For example, let’s say that R0 is 1. If I am infected, then I am apt to infect one other person. That person will go on to infect one other person and so on. The progression is 1+1+1+1. After 20 generations, there are 20 infected people.
However, if R0 is 2, then I will infect two persons who each will go on to infect two other persons. So, the progression becomes 1+2+4+8+16+32, and after 20 generations there will be 1+22+23+24… +220 infected people. In other words, the growth is exponential.
If R0 is less than 1, the disease will die out. If it is 1, it will remain alive and stable – however there won’t be an epidemic. But if R0 is greater than one, the disease will expand quickly and there could be an epidemic. The larger R0 is, the faster the disease will spread.
There are several assumptions, foremost of which is that R0 is only significant if everyone in a population is susceptible to a disease. This means that the disease is novel (new) so there is no natural immunity, there is no way to vaccinate against it, or there is no way to slow or stop the spread of the disease.
The CDC estimates that to 36-51 million people have caught the seasonal flu and between 22-55 thousand people have died from it between Oct. 1, 2019 through Feb. 1, 2020. The seasonal flu has an R0 of 1.3, so it is slightly exponential. After 20 generations there will be 190 infected people.
The H1N1 Spanish Flu R0 is estimated to have ranged from 1.4 – 2.8 (up to 877 million after 20 generations), and SARS was 2.2 (up to 7 million after 20 generations). While the Spanish Flu was not contained, SARs was, and the number of deaths was substantially lowered.
The H1N1 Spanish Flu actually came back came back in 2009 but researchers reported in the journal Science that during its return the R0 value was between 1.4 and 1.6. The existence of vaccines and antiviral drugs made the 2009 outbreak much less deadly.
According to the World Health Organization (WHO), a total of 8,098 people worldwide became sick with SARS and 774 died. By late July 2003, no new cases were being reported, and WHO declared the global outbreak to be over.
Remember that we are in the very early stages of COVID-19 and because we are not testing everyone, the R0 only be can guesstimated. As of March 19 2020 the R0 appears to be 2.2 but again, it could be higher or lower. All we know for certain is the numerator (the number of people who have died) and not the denominator (the number of people infected).
So, is this the end of time as we know it or is COVID-19 being blown out of proportion by the media? Italy has seen 41,000 cases, 3,400 deaths and 4,400 recoveries. The United States has seen 12,000 cases, 176 deaths and 108 recoveries. What’s the difference? Some pundits are saying socialized versus private medicine while others are saying that Italy’s hardest-hit regions were full of older people with underlying conditions.
The US CDC concurs that older adults and those with heart disease, diabetes or lung disease are much more prone to suffer from the disease. Unfortunately, there is not much more that is known at this time and until we do know, perhaps the safest course is to try not to catch it until we do know. And that means following the authorities when they tell you to socially isolate yourself.
As my ex-father in law used so say, “if you cannot be safe, be hygienic.” For first responders, it’s hard to isolate yourself against the virus since you are out and about every day. But you can be hygienic. If your CO has no objections, hang a bottle of hand sanitizer from a belt loop or your vest. Use it and use it frequently. Wash your hands with soap and water every time you get the chance. Remove your uniform and wash your hands and face as soon as you can after getting home. Even better, take a shower as soon as you’re home.
Remember that WW II phrase, “We Can Do It!” We still can.