What is the R-naught (R0) value?

R-naught (R0) is the Reproduction number of a disease.  It’s a measure of to how many people an infected person will spread the disease into a population that has little or no immunity.

  • If R0 is less than 1, each existing infection causes less than one new infection: The disease will decline and eventually die out.
  • If R0 equals 1, each existing infection causes one new infection: The disease will continue in the population but there won’t be an epidemic.
  • If R0 is more than 1, each existing infection causes more than one new infection:  The disease will spread and there is a high probability of an epidemic.

What was the R0 of the 1918 Influenza Pandemic?

In 1918, the Swine Flu (H1N1 virus)  had an estimated R0 value in the U.S. of  between 1.34 to  3.21.  Among sailors it was as high as 4.97.

When the swine flu, or H1N1 virus, returned in 2009, the  R0 value dropped to around 1.4 to 1.6, still pretty contagious but not as bad as 1918 because many people had some measure of immunity.   The 1918 pandemic killed an estimated 50 million people worldwide. One contributing factor was apathy by public officials in the beginning and the continued transportation of solders back and forth from Europe.

SARS-CoV-2 virus causes the disease COVID-19

This virus is apparently new to humans although it is known to exist in animals and similar strains have been isolated and stored in containment laboratories around the world, such as those in Galveston Texas, and Wuhan, Hubei, China. These laboratories are classified as Biosafety Level 4 laboratories where the most virulent and dangerous pathogens are safely stored for research purposes.

Genetic research on the SARS-CoV-2 virus recovered from patients suggests that the variant causing the pandemic is  similar to that recovered from horseshoe bats but as of May 2020 its origin and direct ancestral viruses have not been identified.

What is the R0 of  SARS-CoV-2?

The only totally reliable way to know the R0 of  SARS-CoV-2 is to wait until the end of the pandemic and then survey various populations around the world. It will vary from one population to another.

Judging from the reaction of health authorities around the world, it is perceived to be around 2–3, suggesting  that 50–60% of the population will eventually be infected because nobody appears to be immune.  As more people are infected and recover, the pool of carriers diminishes and the pandemic slowly dies out. Before that can happen, vaccines will be developed and susceptible populations can be vaccinated.

Vaccines that are now approved in the West appear to be around 95% effective in imparting immunity.

Here is a good paper from the Royal Society published in August of 2020 that details the complexity of arriving at a number.  This was published before newer, more contagious, variants started to circulate:


The above file opens in  PDF

What does the President of France Have to Say about Covid-19?


Après la crise, la fin de la bise?


Best Estimates of R0 for SARS-CoV-2

Updated January 4, 2021

With the advent of a variant of the Covid-19 virus dubbed B 1.1.7 that has spread rapidly across the U.K., there is a lot of new interest in comparing the R0 of the new variant with the original variants that originally infected Washington State and the East Coast. The existence of numerous variants may be the reason that a single R0 value has not been widely agreed.

From cases of the B 1.1.7 variant found in Colorado, it appears that the R0 of this variant is approaching 2.

Earlier Estimates

Medical News Today reported a study buy  Joacim Rocklöv, who is a professor of sustainable health at Umeå University in Sweden. They analyzed 12 studies that they regarded to be of high quality. Their conclusion was that SARS-CoV-2 likely has an R0  ranging from 1.4 to 6.49!  The World Health Organization estimated it between 1.4 and 2.5. Differences can vary depending on how calculations are made. Some use statistical methods; other simple mathematical calculations.

Calculating the R0 of a disease involves knowing how long the infectious period lasts, how long infected people are in contact with susceptible people, and how the disease is physically spread.  COVID-19 produces huge amounts of virus in the upper respiratory tract before a person even feels sick. Sneezing and coughing at this early stage spreads the virus far and wide.


Wearing a mask does not prevent you from contracting the disease: it slows the spread, along with other measures.  A sick person does not know she is sick. She sneezes and despite wearing a mask, virus is spread far and wide. The good news is that the viral load varies as the square of the distance. The farther you are away from that person, the smaller viral load you will receive. Theoretically if your immune system is in peak condition, you may be able to handle a small inoculum (viral load).  It makes sense to stay as far from people as possible.

Fortunately, the same measures that help prevent the spread of flu and the common cold, also reduce the spread of COVID-19:  frequent and thorough hand washing; not touching your face;  coughing and sneezing into a large tissue or towel, or better yet cough outside far from people; staying out of crowds or maintaining larger than customary distances from people.

Doing all of these things will reduce the R0 of COVID-19, and will allow hospitals to keep up with the inevitable severely sick people.

Recent Developmenst Treating Covid-19

A funeral establishment is not the best source of information about how to avoid Covid-19 or how to treat Covid-19, so here is a link to a site that has withstood initial skepticism and is now widely admired as being pioneers in the treatment of the disease.



Download the latest protocol by Doctor Paul Marik and his team:  PROTOCOL

Update – June 13, 2021

There are now numerous variant strains of SARS-CoV-2.  Naming the variants has been a bit “slapdash” as described on the-Scientist.com website.

The original B.1.1.7 strain is now called Alpha and is the strain described above in the description of R-naught.

B.1.617.2 that originated in India is now called Delta. It has an R-naught reported to be 6, well above the 1.3 finally reported for  Alpha in European countries.

Covid-19 has been a great learning experience, especially for those interested in epidemiology and the mathematics of calculating the velocity of a disease spreading through a population. Such information could have great economic value. But human nature and virus mutation diminished the predictive value of R0. In a quest to achieve “herd immunity” governments have urged universal immunizations only to be met with opposition as high as 50%.  Under such circumstances it is very difficult to estimate an “effective reproduction number.”

The basic reproduction number (R0) is an epidemiological concept that measures the spread of an infectious disease where nobody is either immune or vaccinated. It is defined at the start of an outbreak.  Rt is the reproduction number over time.  HERE  is a site that attempted to track Rt. They now defer to other sites that are keeping up with the statistics.

HERE for example.


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