COVID-19 Comparator

By Boris Dalstein. Published March 24, 2020.

Last Updated (article): March 25, 2020.

Last Updated (charts data): May 05, 2020, 11:26 AM (UTC).

Source code: github.com/dalboris/covid19comparator

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The province of Hubei in China waited 40 deaths before entering lockdown, for a final death toll of 3,000. Without the lockdown, it could have been 120,000 deaths, if we assume that 40% of the population would have been infected with an infection fatality risk of 0.5%. So we know that lockdowns work, but acting early is critical. For example, Italy waited 600 deaths, and is on a trajectory to have more than 10,000 deaths (6,820 as of March 24).

Indeed, at the early stage of any epidemic, the death toll grows exponentially, which means that each day, the death toll is increased by an (almost) fixed percentage, called the growth rate. In the case of COVID-19, this growth rate is typically around 30%, which means that the death toll doubles every three days. Let's take the United States for example. You can see how every three days, the death toll doubles:

Total

Deaths Growth

Rate 57 68 +19% (57 × 1.19 = 68) 86 +26% (68 × 1.26 = 86) 109 +27% (86 × 1.27 = 109) 150 +38% (109 × 1.38 = 150) 207 +38% (150 × 1.38 = 207) 256 +24% (207 × 1.24 = 256) 302 +18% (256 × 1.18 = 302) 413 +37% (302 × 1.37 = 413) 553 +34% (413 × 1.34 = 553) (avg.: 28.7%) (57 × 1.287^9 = 553)

Data: worldometers.info/coronavirus/country/us

Obviously the growth can't be exponential forever. It stops either once most of the population is infected (example: 120,000 deaths), or once the country succeeds in stopping the propagation (example: 3,000 deaths). Unfortunately, even when a country enters lockdown early, this exponential growth typically doesn't stop before at least 14 days after lockdown, which corresponds to the median time from first symptom to death. Indeed, most deaths in this 14-day period after lockdown are from people that were already contaminated before the lockdown. So if a country currently has 100 deaths with a growth rate of 30%, and enters lockdown today, the death toll is expected to be at least:

100 × 1.3 × 1.3 × ... (14 times) = 3,937 deaths

But if they wait 7 more days, the death toll is expected to be at least:

100 × 1.3 × 1.3 × ... (21 times) = 24,706 deaths

Note: the final death toll will depend on many factors, such as population density, cultural norms, age demographics, whether hospitals will be in shortage of ventilators and ICU beds, and whether softer measures where already in place a few days/weeks before the lockdown, such as closing schools, disallowing mass gatherings, etc.

This is why every day counts. Countries which are suffering widespread infections must enter lockdown as soon as possible. If your government doesn't order a lockdown, please self-quarantine, to take matters into your own hands. Stay home, to save the lives of tens of thousands of people, if not hundreds of thousands or more.

Below, you can compare the number of deaths in different countries. This comparator allows you to see for yourself how scary exponential growth is, and understand why it is so important to enter lockdown as soon as possible. Remember, the death toll is expected to keep growing exponentially for 14 days after lockdown, which is why if you are not doing it already, you should start staying home now, even if the number of deaths in your country doesn't look scary yet. Exponential growth is deceptive: it looks slow at the beginning, but then in a matter of days you get thousands of deaths.

Data: Johns Hopkins University

Note 1: this is a work in progress, more functionality should be added little by little.

Note 2: different countries have different testing policies, so you can't directly compare the number of confirmed cases between countries, nor you can compare their case-fatality ratio. However, the number of cases is useful to estimate the growth rate in countries where the number of deaths is still too low to be able to do any meaningful statistics. Also, the number of cases is useful to detect trend reversal on a per-country basis: the number of cases typically stops being exponential before the number of deaths, due to the delay between first symptom and death.

Note 3: the true infection-fatality risk (what are your chances of dying if infected) is typically lower than the current case-fatality ratio (ratio between confirmed deaths and confirmed cases) since many people are infected but not tested. However, it may also be higher, since some people have already been tested positive and haven't died yet, but may die in the coming weeks. Taking all that into account (estimation of number of people really infected, and delay between infection and death), epidemiologists estimate the true infection-fatality risk of SARS-CoV-2 to be around 0.25%-3%, which is 10-100 times more deadly than the average seasonal flu (~0.03%). Of course, there is a possibility that despite the best efforts of our scientists, we are largely underestimating the current number of infected people (and thus overestimating the true infection-fatality risk), such as argued by this study. However, most studies don't support such an optimistic scenario.

Note 4: without aggressive social distancing measures, SARS-CoV-2 may infect 40%-70% of the population, not just ~10% like the seasonal flu, since no one has immunity and there is no vaccine yet. This means that it has the potential to kill more than 50 million people worldwide, not just 500,000 like the seasonal flu or the 2009 H1N1 flu pandemic. In fact, this is the most dangerous respiratory pandemic since the 1918 Spanish flu. Fortunately, most countries are indeed taking aggressive social distancing measures as recommended by the scientific community, so we should end up nowhere near these worst case scenarios.

Note 5: even though this pandemic is really bad (possibly the worst in the past 100 years), we've been through worse in history. This is not an apocalypse. Countries won't collapse. Life will go on. Every year, worldwide, there are approximately 140 million births and 60 million deaths. So there is no need to panic: all we need is to do is to try to save as many people as possible by acting rationally and taking effective actions based on best available scientific knowledge. And this is exactly what most countries are doing with these lockdown measures. We'll get through this, don't worry. But do stay home to save the lives of as many people as possible, especially the people you love and live near you.

What does "stay home" mean?

If you live in a country which is affected by coronavirus (for example, 5-10 deaths already), you must absolutely stay home. Not only does this protect you, but perhaps more importantly, it protects everyone else. Indeed, it is impossible for you to know that you are not contagious, as it seems possible to have zero symptoms but still be contagious. Since it is impossible for you to know whether you are contagious, you must act exactly as you would if you knew that you were contagious. You must act exactly as you would if you knew that each contact with another human being might kill them directly, or infect them and indirectly kill other people.

Do not go to public places, unless strictly necessary for your survival (such as buying food or medicine), or strictly necessary for not losing your job. In particular, don't go to bars, coffee shops, restaurants, concert venues, theaters, discotheques, gyms, swimming pools, etc. Avoid public transportation at all cost unless, again, it is strictly necessary for your survival or not losing your job.

Stop seeing your friends and family members unless you already live under the same roof, or unless they cannot go shopping themselves and depend on you for their survival. We know, this is by far the hardest part. But by not seeing them, you protect them, and you protect the people around them. Remember, there is a very real chance that you are infected and contagious without knowing it. Call them as often as you please.

Do not practice any sport requiring more than one person: gym alone in your living room is okay, but tennis is not okay (you touch your face, then the ball, then your opponent does the same). Any team sport is obviously not okay. Importantly, don't go skiing, climbing, or any activity where the risk of injury might strain the healthcare system, which is already, or going to be, over capacity.

It is okay a take a daily 15-min walk or run in the direct proximity of your front door to get some fresh air and exercise once per day (or walk your dog), and not go insane. But stay 6-feet/2-meter away from other people. Do not hang out in parks. It's okay to walk/run in a local park if it is part of your daily 15-min outdoor routine, but do not seat on any bench, or hang out there. In particular, do not meet any friends or family members in a park, or anywhere.

Very importantly, do not travel, by any means of transportation, unless for buying food/medicine or go to work. Don't use your car, don't use your bike, don't use your electric scooter, don't use your skateboard. Using any means of transportation for non-essential activity means traveling too far from home and potentially carrying the virus to new places where it hasn't been yet.

If possible, do not go to school/work. Try to see with your boss whether it's possible to work from home. However, please do not lose your job over this: just hope that your political leaders close your workplace as soon as possible. If at work/school, try to stay 6-feet/2-meter away from anyone, and wash your hands as often as possible (e.g., every hour). The virus can stay contagious on surfaces (e.g., door handles, keyboards) for days. Obviously, do not shake hands or hug anyone at school/work.

We know that this is not easy. We don't like changing our habits. We don't like not seeing our loved ones. We don't like canceling trips. We don't like canceling weddings. But we're hundreds of millions of people currently doing it around the world (either self-imposed or imposed by our governments), and really, sitting in our couches watching TV alone or with our household for one month is a small price to pay to stop the pandemic, and potentially save the lives of hundreds of thousands of people.