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Public Health

Covid19 – The 42 day theory

While India has managed #Covid19 well, yet it takes 42 days for the virus to slow down reasons Sanjeev Prakash in this analytical piece…

India has extended its lock-down by another 19 days. This effectively means that for 40 days 1.3 billion people will technically stay at home to fight an unknown enemy. This has been unprecedented and may have major impacts on the nation in various ways. In my article I will take the reader through the 42 day theory which explores when the rate of new cases starts slowing down. I will also take the reader through some encouraging and worrying signs in a few Indian states.

Before we go any further, we would also like to share the Covid19 Projection Model (CPM19 performance). On April 8th the model projected India’s cases to reach 9K by 15th April. India stood at 11.4K cases. This bump can be attributed to the huge number of cases reported on 13th April.

The 42 day Theory

While observing the data, we had theorized that it has been taking an average of 42 days (after reaching 100 cases) for a country to slow its growth rate. Definition of Slow Down – Bring the rolling 7 day average of daily growth% of new cases to less than 5%. Roughly this is when the curve has been observed to have flattened. 

To study this hypothesis we considered India, Italy, USA, Iran, Germany, Spain, France and Sweden. Sweden is a new addition as we wanted to include a country with minimal restriction in terms of lockdown.  We removed South Korea as it seems more of an outlier. 

We defined the day the country reached the 100th case as “T”. Thereafter we looked at growth rates on a day to day basis. One week after T would be T+7. We then sought to identify the day the  moving average dropped below 5%.

What we observed

Italy

Italy took 41 days after reaching 100 cases to bring its 7 day rolling average to below 5%. Italy has reported on an average 3.8K cases per day since then in these 12 days. This number for the previous 12 days before the 42nd day was at 5.1K per day. 

To get the numbers in perspective, 24 days ago, Italy reported 5560 new cases. Yesterday, Italy reported only 2667 cases. 

Iran

Iran took 43 days after reaching 100 cases to bring its 7 day rolling average to below 5%. Iran has reported on an average 1.7K cases per day since then in these 8 days. 

This number for the previous 8 days before the 43rd day was at 2.6K per day. To get the numbers in perspective, 16 days ago, Iran reported 3110 new cases. Yesterday, Iran reported only 1512 cases. 

Spain

Spain took 39 days after reaching 100 cases to bring its 7 day rolling average to below 5%. Spain has reported on an average 4.6K cases per day since then in these 7 days. This number for the previous 7 days before the 39th day was at 6.3K per day. Spain has seen an anomalous day yesterday as the number of new cases shot up to 6.5k after going steadily down. How this pans out is yet to be seen

Germany

Germany took 40 days after reaching 100 cases to bring its 7 day rolling average to below 5%. An average 3K cases per day have been reported since then. This number for the previous 7 days before the 40th day was at 5K per day. To get the numbers in perspective, 14 days ago, Germany reported 6813 new cases. Yesterday, Germany reported only 2543 cases. 

France

France has just gone below the 5% threshold, two days ago so we need to study it to make sure there is no erratic behavior.

USA 

The USA is currently on its 45th day. Right now it’s showing a 7 day rolling average of 5.8%. We believe it will go below the 5% mark by the 48th day

Sweden

Sweden is currently on its 41st day and its 7 day rolling average  yesterday was 5.1%. We believe it will go below the 5% mark today i.e. on the 42nd day.

Based on this we postulate that an average it takes 42 days for a country to really slow down the growth of new cases reported.

To see where India fits in these trends, we tracked the maximum and minimum 7 day rolling average of the daily growth rate each day for all the countries.

For example if on a particular day Italy’s 7 day rolling average of the daily growth rate was 25% and it was the highest for that day it was considered as MAX value. Similarly we arrived at a MIN value. 

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Hence we had a MAX and MIN value for the day along with the average growth rate for all 8 countries. This gave us the outer limits and we tried to see how India’s curve fit within these limits. (See Graph)

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As you can clearly see that India is pretty much following the average path, we can easily postulate that India may fall below the 5% threshold by the 44th day after reaching its 100th cases. We are currently on the 32nd day. This means that by 28th April 2020, we should definitely start seeing a very visible slowdown. This is also corroborated by the CPM19 model that we have worked upon.

Encouraging Signs from Indian States

When we look at the trend in the last seven days for the Rolling Average of daily growth rates, there clearly emerges encouraging trends from a few states. (See Graph)

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Kerala has clearly flattened its growth rate below 5% and it seems to be on the path to recovery. The remaining 4 states AP, Kar, Tel and TN are showing signs of slowing down. Haryana is another state that has shown vast improvement in the last few days. These states will pull down India’s growth rate. What has definitely worked in these states is the high level of contact tracing. Ker, TN, Kar and Har have started doing door to door tracing in the containment and hot zones.

The worry zones

Maharashtra and Delhi remain a concern, but as we had mentioned in our previous article there were a few states like MP, Gujarat and Rajasthan that were showing early signs of growth. These states now have full blown growth of new cases and their 7 day rolling average is now higher than Maharashtra and Delhi. 

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Although it may be premature but Maharashtra and Delhi may be showing some signs of slowing down. But MP, Raj and Gujarat may spoil the gains from the slow down of the above two states. 

What’s Next For India

With the extension of the lockdown, India has bought some time. If we follow the trend we should be looking at slowing down the rate of growth after around 25K+ cases. Even if we slow it to a daily growth of 1% we will still be adding 250 new cases daily. This will only be possible in an extended lockdown. Eventually, due to economic factors lockdown will be lifted and we may see a second wave.

The situation for India seems bleak because then the second wave would mean that our medical system will be stretched tremendously.  At whatever level possible restricted movement and social distancing will continue to be the main tool to manage the pandemic in India. Or else, we should seriously hope that the hot Indian weather has an effect on the virus and that it disappears completely.

About the Author

Sanjeev Prakash is an Analytics and Marketing professional with more than 12 years of experience in Analytics, Data Management, Sales, Brand Management, Corporate Communications, Market Research and Customer Relationship Management. Sanjeev has an MBA from IMT Ghaziabad and a degree in economics.

(Also published on LinkedIn- https://www.linkedin.com/pulse/covid19-42-day-theory-sanjeev-prakash/?trackingId=dR%2FJUX2nQ0CyD7v0iG69Ew%3D%3D)

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