One aspect of COVID-19 that has surprised experts and the general public alike is the speed of its spread. Regardless of the robustness of each local health system, the virus has managed to reach (almost) every corner of the planet in less than a quarter. Mathematics warns of the dangers of exponential growth, and immediately multiple doubts set in. What is the best strategy to contain COVID-19? Are “lockdowns” as effective as we think? Does limiting social interaction help? An online simulator helps us find the answer.
The Numbers Behind the Spread
On February 15, the United States had just 15 cases linked to COVID-19. By March 1, that number had jumped to 76. Today, the latest report confirms 3,689 cases. A month difference from one extreme to the other. In the past we have explored the effects of exponential growth, but unfortunately we can no longer talk about grains of rice. There are sick people, a lot of paranoia, and collapsed health systems. Without precise controls, using a simple calculation like doubling the number of sick people every 72 hours, the United States would have a million infected in May.
A Simulator to Understand the Options
To visualize this a bit better, the folks at The Washington Post shared a simulator based on a hypothetical disease called “simulitis” that develops in a town with a population of 200. The conditions are a bit more aggressive: every healthy person falls ill immediately after contact with an infected person, but its mortality rate is zero and everyone recovers:
As expected. The curve of infections begins to grow quickly, and once it crosses the limit point, it starts to fall almost as fast. However, in a situation like the one presented by the coronavirus SARS-CoV-2 and its disease COVID-19, it is logical that authorities try to activate certain protocols to limit its spread. In the case of China, and especially the Wuhan area and the rest of Hubei province, the strategy adopted is a mandatory quarantine. How does that work? Let’s see:
This exercise just reminds us of the impossibility of a perfect total quarantine. There is no such thing as ideal hermeticism: sooner or later, a healthy person will end up interacting with a sick one. The delivery workers of Wuhan are an excellent example. Under a “perfect” quarantine they would not be allowed to circulate, but the population needs basic resources like food and cleaning supplies, while health professionals depend on them to obtain equipment and materials.
https://old.neoteo.com/coronavirus-mapa-interactivo-de-infecciones/The Recommended Path: Social Distancing
The specialists’ recommendation is what is known as “social distancing”. Stay home, limit public gatherings, maintain a minimum distance from others, reduce mobility and direct interaction.
Now, there are people who must go out anyway (security, health professionals, etc.), and others... will disobey, increasing the risk of falling ill and continuing to spread the virus. How does the model react to social distancing with 25 percent of people moving?
Tightening the Measures
The curve is less steep, but it is still there. How do you optimize it? By eliminating the reasons to go out, through the closure of public spaces, large commercial establishments, and anything that allows people to gather. China closed virtually everything. Italy ordered the closure of multiple spaces and interrupted the soccer tournament. The United States is following the same path, suspending and rescheduling events (for example, E3). So, what would happen if only one out of every eight people moves?
The Bottom Line
The curve takes a long time to grow, which frees up resources and helps the recovery process for those already sick. Now, the simulation is just that... a simulation. Comparing this “simulitis” to COVID-19 would be a serious mistake, and we cannot forget the most raw detail: COVID-19 kills people as we write these lines. However, the underlying mechanism is very similar. We can beat this virus; we just need to do things right.
Source: The Washington Post
