Wednesday, March 25, 2020

Why Public Health experts are asking people to practice social distancing

I posted last week on why we are social distancing, and wanted to post on it again to help encourage people to continue to stay at home. There is a little math in this post, but hang with me. I believe it helps to shine a light on exactly why public health experts are asking everyone to stay home.

An important question with an infectious disease is “how contagious is it?”. A good way to measure that is to look at how many people each infected person passes the virus on to.  For the seasonal flu, that is around 1.5 people. So, on average, each person that gets the flu infects 1.5 others.

For COVID-19, that number looks to be around 3. It may be higher than that, because our testing is limited and a lot of people may not show symptoms, but we can go with 3 for this example. So for every person with the virus, they will give it to 3 additional people.

The difference doesn’t seem huge, right? 1.5 vs 3

Let’s do a little math, and think through 10 cycles of infection.  So, one person gets the flu, they give it to 1.5 people. Those 1.5 people give it to 1.5 other people, etc.  How many people would have the flu after 5 cycles?

1 X 1.5 = 1.5
1.5 X 1.5= 2.25
2.25 X 1.5=3.375
3.375 X 1.5=5.06
5.06 X 1.5= 7.59

Now, let’s do COVID-19.
1 X 3 = 3
3 X 3= 9
9 X 3= 27
27 X 3=81
81 x 3= 243

On the 5th cycle of infection, 243 people would be infected with COVID compared to 7.5 with flu. What if we did 10 cycles? I will not write the math out, but the numbers are staggering.

Flu: 57.6 cases
COVID19: 59,049 cases

This is why we are socially isolating. By reducing the number of contacts people have, we can drive down the number of people who get the virus.

People do not give the virus to others on purpose, they spread it when they are unaware they are infected. That could be ANY of us. You may have it. By going out, you may give it to three people, who give it to three people… and so on. Or, you may not have it. But by going out, you may come in contact with someone that unknowingly does, allowing the cycle to continue.

The number 3 is too high.  The fewer people we contact, the more likely we are to drop that number. If we can drop it to 1.5, in 10 cycles of the virus we can reduce the number of cases by 58,992.

Just something to think about as you try to stay  #HealthyAtHome


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