Covid-19 is more than the 3% lethality rate

Why we should focus on flattening the curve, it's not only about the older population, is about the infrastructure itself

When you have a virus spreading at the speed of how the coronavirus is spreading, the health system is not able to cope with new patients. Resources are limited (even in wealthy countries), and if you start diverting them to cases of coronavirus, you will have deaths of people who under normal circumstances would have been treated. This is exactly what happened in some African countries with the Ebola outbreak, which claimed lives not only directly, but also because it concentrated a gigantic, but focused, effort.

If you start shifting human and physical resources to the cases of Covid-19, other diseases will be underserved. It will take longer to treat someone with an infection, cancer patients may get their treatments delayed, births will receive less attention, STD's programs, etc. etc. That is why flattening the curve is crucial with any epidemic of these characteristics, regardless of the context.

The curve I'm talking about is the number of people who are sick over time. If the curve increases very steeply, the health system will collapse. But if the curve is smoother, the health system will be able to keep functioning even though the total amount of people who got sick with the virus is the same. Remember that the 4% lethality rate is assuming people had access to health care. If hospitals would be collapsed, I don't believe this percentage can stay the same. Bear in mind that China built a hospital in a matter of days to be able to host some of the new patients. Can other countries achieve such a feature? On the other hand, human resources won't be trained as quickly as buildings can be built. You probably remember from the news that China was moving doctors and nurses around the country to cope with the increasing demand.

Flattening the curve is to limit the number of new infection cases that appear, one must understand how epidemics evolve over time and what can be done. There are different stages in epidemics, and each one has different approaches to limit the new cases of infection with a virus. Developing a vaccine will take time, perhaps years, and therefore what you would want is to go through the epidemic without saturating the health system, limiting the total numbers of infected and deceased as much as you can.


We can divide an epidemic into three stages, each one with its own characteristics and different required measures.

Stage 1: Containment

The first stage in an epidemic is containment. You need to do your best to prevent the virus from spreading into your society. If, when it started in Wuhan, you would have placed every single person coming from China in quarantine, you would have prevented it from spreading to new countries. Can this be put into practice? Only partially. It also requires a lot of self-restraint and social consciousness. A measure that seems effective is to do screenings at entry points and be ready to test as many people as needed. Temperature is not a perfect indicator, and therefore you have to acknowledge that at some point the virus will go through this fence.

In the beginning, once you start having transmission between people, it is very important to trace all the contacts with infected patients. You can put them in isolation, monitor them. If you manage to stay in this phase for a long time, the rate at which new cases appear is going to be very small. You can see, for example, what Taiwan managed to achieve by controlling its population. This can be achieved only if you have an active state which proactively communicates with companies and with the public explaining the situation. The quicker you react the longer you can stay in this phase and, for other matters, keep business as usual.

Staying in stage 1 is virtually impossible, but it is key to limiting the strain you cause in society and the health system. However, it is also important that you acknowledge that someone sick will go unnoticed long enough and cases of infection will pop up independently and probably you won't be able to trace back all the connections. It's when the second stage begins, which doesn't mean the policies you employed up to now must be stopped.

Stage 2: Community Transmission

Once you are not able to trace contacts for each one of the detected cases, and transmission starts happening from person to person in a community, the second stage begins. In this stage, the exponential growth becomes apparent. Exponential growth means that the number of sick people doubles every a given amount of time. Imagine the number of cases doubles every 3 days, if you start with a someone sick on day 1, you'll have 2 new patients by day 3, 4 by day 6, etc. In one month, just 30 days, the number of people with the virus would be more than 2000 (with a lethality rate of 3%, it's 60 deaths). If, on the other hand, the number of cases doubles every 4 days, in a month you would have 250 infections. Slowing down the transmission rate is therefore of utmost importance.

Coronavirus evolution by country

The image above was taken from this tweet by Andreas Burkert.

You can see countries in which doubling the number of cases happens in a matter of days and countries in which this happens in weeks. And the biggest difference is how they reacted to the epidemic. Flattening the curve at this stage is crucial, and the only way to achieve it is by involving all society in the effort. Remember that even though the lethality rate is higher for older people, we are all susceptible, and the majority of who gets infected will need weeks of care in a hospital. The demand for beds will increase drastically, and it won't be possible to meet it from one day to the other. Not every country has China's ability to make hospitals pop up in a matter of days.

At this stage, the question is how to lower the spread rate, how can you go from doubling the number of cases from 3 days to 4 days or even longer. The only possible path is to minimize as much as possible the contact between people. Remember that the virus spreads only through direct exposure. It's not a mosquito or something you find in the air. There has to be contact between people, perhaps not direct physical touch, but through a surface like a doorknob. To prevent the transmission, bumping elbows instead of shaking hands is just the first step. The true change we can do is to avoid going to places we don't need to go to. Do I need to go dancing tango? Not really, I can skip it for some weeks. This also applies to any crowded place such as churches, cinemas, parties, conferences, etc.

Offices can adapt their practices to allow work-from-home for extended periods, universities can move to online lectures. Meetings don't need to be face to face, etc. It's better to walk or bike instead of taking a bus. However, there's only so much that a person can limit on her own, the true change in behavior happens structurally. If self-quarantining myself has a direct economic impact on me, probably I'll try to avoid it. That is why clear communication from the government to the managers is crucial. Managers, on the other hand, can make the math: 2 weeks off for one employee can save you 2 weeks of downtime of 1000 employees in a month. Does the cost offset the risk?

Once you have community transmission of the virus, many things can be done that don't imply stopping with work. You can ask half of your employees to work from home. For example, doing one week from home, one week from the office. Just this measure limits the social interactions to half, and the exponential growth can be substantially lower. If going from 3 days to 4 days doubling time has a 10X impact on the number of cases, imagine going from 3 days to 6 days? And limiting the number of people in an office also lowers the number of people on public transport, etc. It is a simple measure that can have a large impact.

Italy is now in complete lockdown to minimize the number of social contacts. Was this, however, completely necessary? One can argue that if Italy would have done a better job at stage 1, the containment, and would have started applying policies to effectively reduce the number of contacts, the lockdown would not have been necessary. This would have had a much lower impact on their own economy. Other countries such as The Netherlands, even though they have several weeks of advantage compared to China, for example, don't seem to specifically bother about taking the proper measures. It is not even clear whether they are testing all the people they should be testing. Employers don't get proper instructions, universities, conferences, the Carnival, everything has been business as usual for too long.

Stage 3: Slow Down

At some point, the number of infections will start to decrease. This happens because either a high number of people was infected and thus herd immunity makes it very hard for the virus to keep spreading, or because a vaccine is ready, or because there's also a climatic factor: when warmer temperatures start, it is expected that the transmission of the virus will slow down naturally. It can also be that an effective policy in stage 2 effectively decreases the number of new infections. Once the number starts dropping, the virus will slowly disappear, following its natural course. If no one is sick, then there's no risk of contagion. This is what happened with SARS, after a year of no new cases, it was declared that the virus was finally defeated.

With a virus spreading at the speed Covid-19 spreads, however, it is unlikely that the containment measures will be engouh to let it naturally disappear. Therefore a vaccine probably will be a necessary tool to avoid having stational Covid-19 outbreaks, such as with the normal flu. However, a vaccine won't be ready until at least the next boreal summer, which is more than a year away. If we stop taking precautions as soon as the virus starts easing, it is very easy to generate a rebound. Next winter, or as soon as controls relax, everything will start again.

During this stage, the efforts for containment should not be minimized. The virus is still active and as soon as the conditions are appropriate, there will be again an increase in the number of cases. This is even without considering any possible mutation of the virus which can overcome herd immunity or the possibility of a virus that can infect twice the same person.

What to do

What happens at any of the stages can't be controlled just by individuals. It is the government's responsibility to lay out a plan and execute it in the shortest amount of time. It is not the first time the world is facing such problems in less than 20 years and still, it hits us in the face as very badly prepared. What we can do can also be layered, depending on the role each one has. It is also important to acknowledge that the time scales during which we need to adopt measures are not weeks, but months, and the measures which are necessary change according to the stage of the epidemic.

Single individuals

As individuals, the more important aspect on which we need to be very conscious is not exposing others if we are feeling sick, or if we think we may have been exposed to the virus. For example, if you have someone in your family who is sick, or has a higher chance of having the virus, don't expose others until you are certain. Don't go to work if you have a fever, don't go to a football match if you are not feeling well. Even if basic, in many countries you can find examples of people going to work sick while being carriers of the virus. Sometimes the government itself controls this, and quarantines groups of people out of precaution. Sometimes, however, is the people themselves who need to show restrain. How people behave is closely linked to their economic activity and the way the government communicates.

As individuals, we can also take measures to minimize exposure to the virus. For example, the most likely path to getting in contact with the virus is through the hands, after touching a contaminated surface. Washing our hands with soap is very effective to avoid infection. Cleaning surfaces such as tables, doorknobs, etc. especially in buildings with a large number of people is very effective as well. This is not a big change to our lifestyle, we just need to embrace better practices. If you are dealing with food, for example, you should be extra conscious.

At the second stage of the epidemic, we will need to go one step further, changing some other aspects of our lifestyle. Choosing to bike or walk to work instead of taking public transport limits the exposure to the virus or the chance of us spreading it. Working from home, deciding not to attend to big gatherings, or deciding not to organize big gatherings. This, however, may not be a possibility for a lot of workers, who still need to get to their workplaces to get the full month's salary. Individuals by themselves have a limited range of action, and is necessary that other actors get involved.

Managers, Companies, Universities, etc.

During the first stage of the epidemic, it is of utmost importance that you transmit calm to your employees, students, etc. And calm not only regarding the frenzy of the unknown virus but also that if they are feeling sick they don't need to show up to work. If they have been in contact with potential cases, it is better if they stay home until it becomes clear. Don't pass the cost of the absence down to them. If you are a company which gives a bonus for perfect attendance, make exceptions. If you pay per day, consider quarantine as sick-leave. If you are a University and pass attendance to your students, suspend it. Again, as a manager or a university, just do the math of what would happen if you have 1 sick employee or student, with a 3-day doubling time. Can you really afford the risk of the downtime, without even considering the risk of the loss of life?

An effective measure seems to be monitoring the temperature of people. It is not perfect, but at least it allows you to catch and prevent further spread of some of the cases. I bet more than one student will show up for an exam even if with a bit of fever, just not to lose the semester. Or at work, if you have an important meeting. This form of surveillance shouldn't be necessary if you have developed the proper work culture. But, as a manager, you should also agree that not everyone will embrace the same ethics, and therefore the risk is still there.

Many companies like having programs of social responsibility. They invest money to build a school, donate to some climate fund. An epidemic is also a good time to show how committed they are to social actions. When the epidemic moves to stage 2, it is important to lower the spread as much as possible. Remember, that most social interactions of an adult person happen at work, while for youngsters, they happen in schools or universities. An effective measure to flatten the curve is to limit the number of social contacts a person has throughout a day. For a lot of jobs, this is as easy as favoring (or forcing) work-from-home. Even if as a manager you don't like it, these are extreme times that require everyone's cooperation. It can be structured as half the team works from home one week, and the other half the other week. We already saw the gigantic impact that has going from 3 days doubling time to 4 days doubling time.

Universities can move to online classes, suspend unnecessary activities such as face-to-face meetings, talks, seminars. Suspend the organization of congresses, workshops, etc. Some things can be moved to the virtual space, some can't and will need to be postponed. Flattening the curve does not imply shutting down activities completely. But, for example, if there is a lab in which 10 people work, probably you can send 5 home to write papers and analyze data, and leave the other 5 who are actually performing crucial experiments. Halving the number of possible interactions has an exponential effect on the transmission of the virus.

Before it is too late

Seeing how things evolved in Italy, some parts of Spain, etc. it is possible to think that you'll be facing the same situation sometime soon. If you are not in lockdown mode, yet, it is a very good time to stress test your infrastructure. Force everyone to work from home for a day. Is your IT able to cope with that? Do employees keep their needed documents accessible from outside? Can students attend lectures remotely if needed? If you are in manufacturing, and there's no way of moving to remote, start laying out a plan for what would happen if half your employees can't show up at work. Are you able to re-arrange production, allocate resources to the important processes? The sooner you start thinking and planning, the smoother your business will run, and the bigger competitive advantage you'll have. Hopefully, the country in which you are won't reach lock-down mode, but better be ready.


The first task a government has is to communicate as clearly and as often as possible. There should be one clear message, coming from one clear person (or institution). Don't let media start finding their own experts, and loose control over what is expected from society. A virologist may not be an epidemiologist, and when asked about certain topics, that person may just not be the more appropriate to answer. Therefore, you need to lay out a plan, communicate it to the different actors, also to society as a whole, and be ready to change the approach if things are not working. As a government, you are responsible for every stage and everything that happens, and therefore you need to act responsibly. At stage 1, monitoring the ports of entry is entirely your responsibility, in much the same way that tracking down contacts. The more information you have, the better prepared you'll be. Run as many tests as possible, and quarantine the people who may have been exposed until you have more information.

Of course, your job is also to lay out policies that will make your life easier. For example, guarantee that employees will get payed full salaries even if they are quarantined. Stress how important it is to stay home if feeling sick. Run campaigns of information. In principle, what you want to avoid is a lockdown. You would want your country to be economically active during the epidemic, you would want your health system not to collapse, and, I hope, you would like to minimize the number of deaths. There are plenty of choices, such as minimizing the bureaucracy required to get sick leave. Be sure to offset the responsibility and cost from individuals to companies. Work in very close contact with the entire health system to understand what is happening. And, again, never stop communicating. Release as much data as often as possible. Prepare the educational system for the long absences of teachers and students.

It is important that at every stage of the epidemic, governments communicate what is expected, and what measures can help. I've seen, for example, that during stage 1 some group lessons were suspended for 2 weeks. This happens because it is what they saw in other countries and think is the sensible thing to do. The issue is that these classes are the sole income of the teacher, and thus it will be a month with half the pay. The issue is that the measure was taken too early when there was not a real need yet, and there is a very likely scenario in which these lessons will need to be suspended again later on when it is much more needed. The second time, perhaps, the teacher can't just afford the money lost. Therefore clear, effective, and timely communication is the best choice, always.


The is no cure for Covid-19 yet, which means we need to deal with it. Therefore all our efforts need to be focused on flattening the curve as early as possible. This task requires efforts from every actor in society, but the only way in which it is going to be a successful strategy is if there is a central coordinator, such as the government. Performing tests, deciding what to close or suspend, and when, is the responsibility of the government. Companies can do only as much until their own financial interests are hit. Early reaction to an epidemic is the best strategy to go through it without the need of a generalized lockdown.

Aquiles Carattino

I am the creator of Python for the Lab

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