In a rare piece of good news about Covid-19, a team of infectious disease experts calculates that the fatality rate in people who have symptoms of the disease caused by the new coronavirus is about 1.4%. Although that estimate applies specifically to Wuhan, the Chinese city where the outbreak began, and is based on data from there, it offers a guide to the rest of the world, where many countries might see even lower death rates.

The new figure is significantly below earlier estimates of 2% or 3% and well below the death rate for China based on simply dividing deaths by cases, which yields almost 4%. While it is still higher than the average 0.1% death rate from seasonal flu, it raises hopes that the worst consequence of the coronavirus will be uncommon.

Cutting against that optimism is the expectation that, because no one was immune to the new virus, “the majority of the population will be infected” absent the quick arrival of a vaccine or drastic public health interventions such as closing public places and canceling public events, the scientists conclude in a paper submitted to a journal but not yet peer-reviewed.

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The expectation that a “majority” of a population will become infected reflects a worst-case scenario about who encounters whom, something modelers call “homogeneous mixing.” But even the more realistic assumption that not everyone mixes with everyone else means that “at least a quarter to a half of the population will very likely become infected” absent social distancing measures or a vaccine, conclude Joseph Wu and Kathy Leung of the University of Hong Kong, leaders in the modeling of infectious diseases, and their colleagues.

The Covid-19 pandemic is sparking efforts to calculate how deadly this new disease is. One measure is called a case fatality rate. While the formula is simple, it’s difficult to get a precise answer.

The better news involves fatality rates. To calculate those, the researchers used data from Wuhan, especially the age distribution of 425 early cases and 41 early fatalities there.

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The chance of someone with symptomatic Covid-19 dying varied by age, confirming other studies. For those aged 15 to 44, the fatality rate was 0.5%, though it might have been as low as 0.1% or as high as 1.3%. For people 45 to 64, the fatality rate was also 0.5%, with a possible low of 0.2% and a possible high of 1.1%. For those over 64, it was 2.7%, with a low and high estimate of 1.5% and 4.7%.

The chance of serious illness from coronavirus infection in younger people was so low, the scientists estimate a fatality rate of zero.

As physicians and researchers have seen since the start of the outbreak, many infected people never become sick. As few as 14% of people in Wuhan with early coronavirus infections were being detected, said epidemiologist Jeffrey Shaman of the Mailman School of Public Health at Columbia University, who led a study published on Monday in Science on undocumented coronavirus infections.

“I think there are many more than the [nearly] 70,000” confirmed Covid-19 cases in Hubei province, Shaman told reporters.

That means the “infection fatality rate” — deaths among people who have the virus but might or might not show disease symptoms — is even lower than Wu and his colleagues calculate.

Despite Wuhan’s heroic efforts to treat patients, the suddenness of the epidemic overwhelmed hospitals there, much as it has in northern Italy. In countries that got more advance warning and prepared better, especially if social distancing succeeds in “flattening the curve” enough to dampen what would otherwise be a tidal wave of Covid-19 cases, the death rate is likely to be lower still.

“Fatality risk estimates may not generalize to those outside of [Wuhan], especially during subsequent phases of the epidemic,” Wu and his colleagues write. “The increasing availability of newer, and potentially better, treatment modalities to more patients would presumably lead to fewer deaths.” That’s true even within China, they find: “To date, the death-to-case ratio in Wuhan has been consistently much higher than that among all the other mainland Chinese cities.”

Lest anyone be tempted to downplay the threat, the scientists caution that Covid-19 is on track to infect millions of people. If social distancing fails to dampen the number of cases at any one time, overwhelming health care systems, the death rate would be higher.

  • So basically, what many of of you are trying to saying is that the WHO and almost every other country in the world has got it wrong. That every country that has “shut down”, that have put their economy at a stand still or in recession, that have put thousands of people’s live on hold and jobs and future at risk have done so because of mass hysteria?

    I think time you ask yourselves what makes more sense?? Obviously, if you are more worried about the economy than with lives, then forget I asked the question.

  • This article is arguing that the mortality is likely to be much lower than the expected 3.5% but citing a study of 425 patients where 41, or nearly 10%, died. That’s a bit odd.

  • So the death rate of the seasonal flu is 0.1% without severe quarantine measures. The death rate of the Corona in Italy at the moment is around 8-9% and rising with complete shutdown of the whole country in order to make it easier on their health care system. It’s true that most Corona cases are undetected, but the same applies for the seasonal flu too, so we can scratch that argument off. I’ve read some reports that this virus is 2-3 times more contageous, but honestly, this looks like a severe underestimation. It’s spreading like wildfire and it’s so much deadlier that the only way to stop it is to lock everyone in their homes. Not to mention that this is only the beginning. The comparison with the seasonal flu is absolutely ridiculous. The numbers alone clearly show that the Corona is HUNDREDS of times more dangerous. If you want to compare it with something the Spanish flu is a good candidate. It killed between 50 and 100 million people. It affected 1/3 of the world’s population, while experts say that the Corona would probably affect 2/3. Back then health care was in a different realm altogether, but so was the movement of people across the globe and within communities. The genie is already out of the bottle and the whole world is lit up. Even with today’s advanced medicine, without lockdowns the death toll may even surpass the Spanish flu because the population is much denser and much more interconnected. The health care systems would be able to provide help to only a minor part of the infected and the death rate would skyrocket. Are you really ready to lose 100 million people or more? Don’t forget that these people support the business you care so much about. And while lockdowns are temporary, when people die, they die forever. You’d lose years and decades worth of potential income from those who perished. Not to mention that if we all go out there and continue doing our business as usual very soon a large number of us will be sick and unable to work anyway. All at the same time. Temporary lockdowns are not only necessary, they are inevitable. If we don’t impose them on ourselves the virus will impose them on us anyway. The only difference is that if we it on our own will we will save millions of lives. It’s actually an easy choice to make. If it wasn’t the most powerful countries in the world would never go there. Some hesitated for a moment only to realize that there really is no other option. Look at the Italians now. They wish they went into a lockdown a month ago.

  • It’s nice to see there are some other logical people here that can understand the outcome of the actions we are taking around the world and what the (I’ll be pessimistic as possible here) 90% of people remaining will have left when were done. This game were playing is far more dangerous than the virus. We would go to war for our way of life, but now want to throw it away for fear. We’ve become a weak and pathetic species it seems, although thankfully there are exceptions. There are logical ways to handle this virus at far less a cost to humanity, but that is being ignored by way of Chicken Little Syndrome.

    • Yes! Whatever happened to “the land of the free and the home of the brave”? What we are doing to ourselves is a cure more deadly than the disease. There is nothing left but to go home, suck our thumbs and take a cyanide pill, our weak little heads pillowed on toilet paper.

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