March 20 – Forecasting COVID-19 in Mississippi

Yesterday I published a forecast for 70 total cases in Mississippi today. That forecast was based on the hope that we could manage to stay below a 50% daily increase in the number of reported cases. Unfortunately, Mississippi continues to see cases increasing by 50-60% each day. I had a bad feeling we would be closer to 80 cases today, and it turns out that my gut was right. Continuing this trend means that we may wake up on Monday morning and find out Friday’s 80 cases have turned into over 250-275 cases. By the end of next week, that number rises to around 1,500 cases.

March 20 – Daily growth of COVID-19 in Mississippi

Slowing the growth rate now is really important. I showed you yesterday how that makes a huge difference in the overall outcome for the people of Mississippi. This graph shows you what can happen if the daily growth rate stays around 50%. It shows the entire population of Mississippi being infected within 30 days. 

Daily forecast of COVID-19 in Mississippi with constant growth rates (next 30 days)

Before you start to panic, let me tell you that I don’t think the whole state will be infected in the next 30 days. There are a variety of reasons why this looks possible in a model but not in reality.

In order for everyone to be infected, every person must come into contact with another contagious person. Our distance and social networks naturally keep us isolated into relatively small groups. Social distancing effectively reduces those interactions even more. I am staying at home except for brief trips into my office. When I do visit my office, my interactions are limited to a very small set of people. Therefore, I cut down potential interactions that would be necessary for the whole state of Mississippi to end of sick in the next 30 days. If I am lucky, I won’t encounter a contagious person at all. Social distancing can both slow the growth rate and cap the number of people who will be infected by the virus.

If you don’t believe any of this is a big deal and are not staying at home, how many cases need to be reported for you to do so? How many people have to be sick, in the hospital, or dead for you to believe? 500? 1,000? What if I told you that by the time we get to 500, you are a week away from having over 5,000 cases? This is why there is a call to “flatten the curve.” As silly as it may seem right now with 80 confirmed cases in Mississippi, it’s time to do your part to slow the spread now.

Don’t fear the green line but be aware of the green line. This is what could happen if we did nothing. If we can manage to cut the growth rate in half as quickly as possible, it has enormous consequences over the long term. Cutting the growth rate in half today would mean the difference between having 524 cases in 10 days or having 4,441 cases in 10 days. 

Cutting the growth rate in half makes a BIG difference!

Disclaimer

I am not a medical doctor, a healthcare specialist, biologist, or public health professional. I am a trained financial economist building an economist growth model and explaining the impact of personal and policy outcomes on that model.

March 19: Forecasting COVID-19 in Mississippi

After a number of conversations yesterday with various people about why there is such a divergence in individual responses to the call for social distancing, I went to my spreadsheet. As a trained financial economist, that’s what we do. We make a model. As it turns out, this is a pretty simple model. The general rule of thumb is that we can expect the number of cases to double every two days. So, the number of cases grows by 50% every day.

When you start to map those numbers out over the next 30-45 days, you start to understand why this is such a big deal. Today doesn’t look that bad. Neither does tomorrow. In fact, it could take a while before most of us even know somebody who is sick. Unfortunately, by the time there are enough people sick that we take notice, it is too late. The impact of doubling every two days is about to get very ugly.

March 18 Forecasts of COVID-19 Cases in Mississippi with 30-50% daily growth rate

At first glance, a 50% daily growth rate (the green line) continuing over the next three weeks doesn’t seem terrible. When you get to Day 21, however, the number of cases can shoot up from 500,000 to 3,000,000. Essentially, that is the point where every single person in the state of Mississippi has tested positive for COVID-19. On the other hand, the long-term impact of slowing the growth rate just a little has enormously important consequences. If we slow the growth rate from 50% daily growth to 40% daily growth (the blue line), the number of cases in the state of Mississippi stays below 500,000 over the next 30 days.

Let’s take a closer look at the next two weeks.

March 18 Forecasts of COVID-19 Cases in Mississippi During the Next Two Weeks

The growth and number of forecasted cases remains small over the next week. People are easily lulled into a sense that this is much ado about nothing. It’s going to take another 7-10 days before the growth in cases reported becomes noticeable by the public. It could take another 2-3 weeks before you even know somebody who tested positive for COVID-19. On the other hand, you also see how meaningful social distancing over the next two weeks can drastically reduce the number of cases in the state. This is illustrated by the difference between the green line 50% daily growth) and the yellow line (30% daily growth).

March 18 – Forecasted Number of COVID-19 Cases with 20% – 50% Daily Growth

If you want to see a closer look at the actual numerical forecasts over the next 14 days, I have included that. Currently, I am only using 3 days of data in the model along with the estimated growth rates being given to us by the government entities. If Mississippi experiences a daily growth rate of 40%-50%, this accurately predicted the 50 cases reported as of today, March 19. It predicts a total of 70 confirmed cases tomorrow. Come back tomorrow to get an update.  

Disclaimer

I am not a medical doctor, a healthcare specialist, biologist, or public health professional. I am a trained financial economist building an economist growth model and explaining the impact of personal and policy outcomes on that model. The base data and general growth rates come from the following sources: