Chasing Covid-19 Using Pareto
We know the importance of frameworks in business. We have extended this discussion and suggested that some of these frameworks have a relevance to dealing with the Covid pandemic. Here is another consideration for the epidemiologists drawn from our knowledge of frameworks.
We are all now familiar with “R” the reproduction number that is the average number of people that receive the disease from a carrier. Indeed, we have been told that it is the most important metric in stopping the spread of the disease. We all know that an R value of less than 1.0 is good news because it means each carrier spreads the disease to less than one person so that eventually it will fizzle out.
But this isn’t the full story. What also matters is the “K” value. You see not everybody spreads the disease to the same extent. Someone visiting bars, nightclubs, and restaurants is more likely to be a super spreader than someone who is self isolating but catches the disease from a random visitor. These super spreaders play a disproportionate role in spreading the disease. This is where the K value comes in. It is a measure of the “dispersion parameter”. The higher the K value, the more uniform the transmission – ie everyone with the disease has an equal chance of passing it on. The lower the K value, the more the disease is spread by a small number of people.
The Spanish flu of 1918 had a K value of 0.94 which means that it was spread evenly by the people who were contagious. This is in contrast to SARS (Severe Acute Respiratory Syndrome) which is another type of coronavirus. SARS had a K value of 0.16. This indicates that one person with the disease is likely to infect dozens of others.
Covid-19 is like SARS; it is subject to super spreading. It is why it is critically important to identify such people so that they and the people they have shared time with, can be isolated. Researchers at the University of Hong Kong reckon that Covid-19 has a K value of 0.45. That tells us that 80% of the spread of the disease is by 20% of people with the infection.
This brings us back to the point at the beginning of this blog. In business we are all familiar with the Pareto principle – the principle determined by the Italian economist Vilfredo Pareto in 1896 in which he established that 80% of the wealth in Italy belonged to 20% of the population. This unequal distribution proves extremely useful to us in our businesses. We know that 20% of our customers account for 80% of our revenue. We know that 20% of our effort determines 80% of what we achieve. It is no surprise therefore that 20% of people infected with Covid-19 account for 80% of infections. Which in turn means that tracking and tracing and isolating those people is key to limiting its spread. It is why, when we hear that there has been an outbreak of the virus in Beijing's biggest wholesale market, it is time to lock it down.