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Thanks to Bill and Melinda Gates for supporting SciShow. If you’d like to reflect on the last year and the lessons we’ve learned through COVID-19 that will help us prepare for the future, head to to read this year's Annual Letter.

Near the end of 2020, we got some puzzling but good news: COVID-19 fatality rates have been dropping. Here are a few factors that might help explain why we’re seeing this trend.

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This episode is brought to you by the annual letter from Bill and Melinda Gates.

You can find it at This year's theme is on COVID-19 and presents ideas for how we could better prepare for future pandemics.

Also, this episode was filmed on January 26, 2021. For our latest COVID-19 coverage, you can check the playlist linked in the description. [♪ INTRO]. Toward the end of 2020, we got some puzzling and good news about the COVID-19 pandemic: fatality rates have been dropping in dozens of countries around the world.

And at this point, there are a lot of unanswered questions about why, and if the numbers might start to climb again soon. But there are reasons to think they might not, and that this decline is actually a reminder that everyone’s hard work is really paying off. First, one big reason the fatality rate may be dropping is that we may just have more data.

See, there are two kinds of fatality rates experts talk about when it comes to pandemics: the case fatality ratio and the infection fatality rate. The case fatality ratio is the number of people who were diagnosed with COVID-19 and eventually died from it, divided by the total number of people diagnosed with the disease. We’ve been tracking this number almost since the very beginning of the pandemic, because it’s pretty easy to track: It’s based on diagnoses.

Meanwhile, the infection fatality rate is much harder to monitor. This is the number of confirmed deaths divided by the total number of infected people, whether or not they got sick and got an official diagnosis. And this number is based on antibody tests done on a representative sample of a population — tests that show someone’s immune system has encountered and responded to the virus.

Population-wide antibody studies aren’t available for every country yet, so as we get more data, researchers will probably find out that more people were infected with this virus than we thought. So, the infection fatality rate will continue to drop. But math isn’t the only reason we’re seeing fewer COVID-19 deaths.

Another reason is that we’re just learning how to treat patients better. For example, some COVID patients can have low blood oxygen levels. In other respiratory diseases, that might mean the patient should go on a ventilator.

So, in the beginning of the pandemic, that’s often what physicians did. And ventilators are life-saving technology! But just like every serious medical procedure, there are risks associated with ventilator use, including infection.

And in the last year, we've learned that when it comes to COVID19, ventilators aren't always needed as early as we thought, even for patients with low oxygen levels. We’re still learning exactly why this illness may be different, but it seems that some patients that would normally be put on a ventilator do better with less invasive oxygen therapy for a while. In fact, one of the more effective things has been just turning patients onto their stomachs instead of their backs, known as proning.

In this position, someone’s heart isn’t pressing on the lungs, so the back part of the lungs can expand more fully and help them get more oxygen. And the relationship between COVID and ventilators isn’t the only thing we’ve come to understand better. We also have some other generally-agreed upon treatments, or standards of care.

Standards of care tell physicians and nurses what the best ways to treat someone with a specific disease are, and they also make sure that the same good treatment is used everywhere possible. At the beginning of the pandemic, we didn’t know much about COVID-19, so we tried all kinds of treatments. But now, we know there are some things to give to patients that are really useful — and others that should be avoided.

Like, doctors can give COVID patients a corticosteroid like dexamethasone. Steroids like this suppress our immune system, which might sound like the opposite of what you would want. But the thinking is that dexamethasone may prevent the excessive, damaging immune response that may happen in these serious cases.

And so far, it’s been found to reduce fatalities in the most serious COVID-19 cases by as much as a third. At least, in patients who required oxygen therapy or ventilation. We also know that the broad-spectrum antiviral drug remdesivir can reduce how long someone is hospitalized before going home.

And that can help prevent hospital overcrowding, which means more patients can receive care. On the flip side, trials and testing have also shown us that some drugs we thought would work didn't. But now that we know that, we can stop giving them to patients.

Finally, some researchers also hypothesize that public health measures like social distancing and face protection, like masks, may be helping lower fatality rates by limiting the dose of the virus someone is exposed to. The idea is that if someone is exposed to a high dose of the virus, it's easier for it to overrun their immune system and start doing serious, potentially deadly damage. So, if someone can limit the amount of virus they’re exposed to by following public health guidelines, it's harder for the virus to get a foothold and cause a fatal case of COVID-19.

We already know that this is probably true for other respiratory illnesses, like the flu. But because there hasn’t been any research into how much of a role this actually plays in COVID-19, this is still a hypothesis. In the end, the chances are good that it's not just one thing causing the infection fatality rate to drop.

It's a little bit of everything, from increased antibody testing, to improved medical care, to just knowing more about the disease and how to treat and avoid it. Now, there’s a long way to go, and this isn’t to say that the current daily death rate is okay. But this is a reminder that in pandemics, these incremental bits of knowledge do add up over time.

And, as the old saying goes, knowing is half the battle. 2020 was filled with incredible hardships, and changes to daily life that affected all of us. So in many ways, it’s encouraging to see things like vaccines being distributed, and standards of care being established. We're also learning a lot that could prepare us for the /next/ pandemic — like what we need to monitor outbreaks, and how to develop treatments faster.

If you’d like to reflect on the last year and the lessons we’ve learned through. COVID-19 that will help us prepare for the future,. Bill and Melinda Gates just released their annual letter.

It looks back on the biggest public health response the world has ever seen and expresses hope that the experiences of the last year can lead to long term change and better prepare us for the /next/ potential pandemic. You can find it at There are specific recommendations on how we can apply the lessons of COVID-19, and what we'll need so any future pandemics don't take us off guard, like investing in research or creating a global alert system for disease outbreaks. [♪ OUTRO].