The math of COVID-19 if we did not adopt social distancing

Our intention is to prompt debate and understanding on the potential spread of 'Novel Corona Virus 2019' (COVID-19, SARS-CoV-2).

The focus of this site is not to provide information on what to do about the virus.   For further information about the virus as information is changing rapidly please refer to the World Health Organization (W.H.O),  the Centers for Disease Control and Prevention (CDC) or your local health authority.   However, please do

1. Wash your hands ideally with soap and warm water for at least 20 seconds approximately every 90 minutes or after touching anything new or personal contact
2. If you cough or sneeze, do it into a tissue, or your elbow, not your hands nor the air
3. Disinfect commonly touched surfaces at least daily
4. Only wear a mask if you are sick, or are a caregiver to someone who is sick (update: early April 2020: Some geographies are recommending masks for all when in public places, please follow local guidance)
5. Stay home if possible, adopt 'Social Distancing'
6. There is a lot of poor information in circulation, please only forward information you know to be true, else please refer people to reputable sources (e.g. WHO, CDC etc)

Please consider watching Last Week Tonight from 16-Mar-2020 for more information. The show is typically satirical, but this episode has a lot of useful information.

The math

Assumptions:

• No social distancing
• The median peak infectious period is understtod to be approximately 8 days after exposure. The median exposure to first symptoms is 5.1 days, it is speculated (CDC estimate) that people can be infectious up to 48 hours before first symptoms but peak spreading likely occurs around day 8 (day 8 is assumed for the data model)
• The average infected person infects 2.28 more people (the reproduction or R0 number). This number is not confirmed and felt to lie somewhere between 2.13 and 4.82; for the math below 2.28 is assumed. Other estimates
• The first reported case was understood to have been observed on 21-Dec-2019. The virus however was likely around several weeks before. For the model below 21-Dec-2019 is assumed as the first case.
• The rate of death is variable per geography. The WHO reported it could be 3.4%, regional data however has the rate of death between 0.95% and 4%. For the model below 2% is assumed
• Between 25% and 35% of all people infected show no symptoms
• These figures are worse case scenario, best case scenario is effective social distancing will lead to zero new infections and 14 days from now ... we have no new infections and within 28 days we have no patients still with COVID-19.   Neither of these two extremes is considered likely

The model ceases at Day 152 because if the virus was to spread to this many people, we are beyond 90% of the total world population.

Items for consideration

As of 16-Mar-2020 which is after China adopted "Social Distancing" but before the benefits of such measures will have tangible improvement elsewhere there were a reported 182,185 total worldwide cases, with 7,148 deaths, and 79,418 recovered. Source.   The model above approximates these numbers, i.e. the model is aligned with what we actually see acknowledging there is a level of under-reporting.

What does this mean?

Simply, if we cannot arrest the spread of this virus it is going to infect many more people. If the R number stays at 2.28 then by the end of May 2020 the virus could have infected every human on the planet. It is acknowledged that will not happen, but 'worse case plans' (e.g. Germany) are projecting for up to 70% of their population being infected.

What do we need to do?

Per there being no vaccine, we must reduce the spread. Social distancing and effective sanitation are the things we need to do.

Hypothetical model

If we could achieve the following:

• For every two future people infected they combined only infect one additional person, i.e. the R0-number is reduced to 0.5 (one new infection for every two infected)

R0: is this the crucial number?

If the R0 number could be reduced to 0.5:

• We project from the 16-Mar-2020 worldwide infection 182,185
• NOTE: These figures assume the virus does not regress naturally per the onset of spring or for other reasons

we get the following

The above table is for NEW infections. Many people infected remain sick for up to 28 days.

Much remains unknown about Novel Corona Virus 2019 (COVID-19, SARS-CoV-2) but due to there being no vaccine, if the virus does not dissipate naturally; our main tool to deal with the virus is 'social distancing'... then if we could achieve a "reproduction number" of 0.5, the virus will be with us through July 2020. If the R0-number is 0.75 the end date would be March 2021.

NOTES:

• Any R0 number greater than one means the virus will not die out without some form of other intervention, e.g. a vaccine, effective anti-virals, or we gain immunity to the virus after recovery.
• Seasonality is not accounted for, for example will the virus shift to the southern hemisphere for May 2020 and return to the Northern Hemisphere in November 2020.

Sample solutions being deployed to sanitize infected areas:

• SteraMist from TOMI Environmental Solutions, deployed in the USA

Global infections (confirmed case count)

Countries rank by case count on 16-Mar-2020 which is the date that the US declared a national emergency.

Since that date the rankings have changed, as of 17-Apr-2020 the top three ranked countries by case are (1) USA, (2) Spain and (3) Italy; on the same date, the top three countries in terms of deaths related to COVID-19 are (1) USA @ 33,284 deaths, (2) Italy @ 22,170 deaths and (3) Spain @ 19,315 deaths.