## Why is Social Distancing so Important ??

As on Apr 2nd, 2020 (the published date)

Mr. President downsizes the impacts of the COVID-19 pandemic. Honourable President justifies a few thousand deaths due to Coronavirus by comparing it with the deaths occurring due to the Flu which is more than 50,000 yearly in the US. Is this ignorance good for America? Well, seeing this ever-increasing exponential curve, it is being foolish to compare coronavirus with regular flu, we will have to pay a huge cost for this. There are 5 things which set this pandemic apart.

1) Highly contagious, (Ro = 2.5 for COVID-19; Ro = 1.3 for flu)

2) No vaccine/defined cure owing to the novelty

3) Un-preparedness of the medical equipment facilities owing to the novelty.

4) 5-10 days Incubation Period. (1 to 2 days for Flu)

5) 10 times mortality rate than Flu.

Because of the high Incubation Period, an infected person remains healthy until 5-10 days. During this period, he may have gone to the office, attending the wedding, done parties etc., infecting 500 other people. Hence the governments across the world are putting pressure on “Social Distancing”. Let’s understand what this is exactly, how it could impact the rate of spread of disease using a simple equation of the exponential epidemics, rather than going into complex models.

Nd = Total No. of cases by a given day

E = Avg no. of people, someone infected is exposed to each day

P = Probability of each exposure being an Infection

Δ Nd= E * P* Nd

Therefore, Nd+1 = Nd+ E * P* Nd

Nd+1 = (1 + E*P) Nd          Nd+n = (1 + E*P)n Nd

The only thing which we can change here is E, that is through Social Distancing. Rest all is constant. Let’s assume we continue the same amount of social distancing we did in the last week (Mar 25th to Mar 31st). Avg E*P in the last week is 0.178 as calculated below:

Table 1

As on Apr 1st, we have 215215 cases in the US. Let’s find out how many cases we may have on Apr 15th, if we keep E*P = 0.178, assuming the same Social Distancing is maintained.

(Note: Ignoring the lag between getting infected getting tested for simplicity, though it matters a lot)

NApr15 = (1 + 0.178)14. 215215 = 2,132,586 = 2.1 million cases which is really frightening

Say, if we practice stronger social distancing reduce E:

We can observe how drastically the cases reduce when E*P is even slightly reduced. As per the advisory, currently, we are allowed to get exposed to a maximum of 10 people every day. If we reduce the exposure to half, ie. 5 people (although 0 is advisable), we can slash the cases from 2.1 million to just 0.7 million which is a huge difference.

 E*P Cases on April 15th 0.178 2,132,586 0.150 1,522,798 0.125 1,119,458 0.100 817,279 0.050 426,111 0.025 304,093 0.0178 275,516

Table 2

Hence, it is the need of the hour that an even stricter lockdown is implemented to reduce the growth rate flatten the curve little earlier than expected. For the people staying in less infected areas, they may be a few days behind, or they aren’t tested much which is even more dangerous. Quarantine rules are applicable equally for all the Americans irrespective of their geographic area.

Let's hope these predictions aren't true. Stay quarantined. Stay safe.