USA Today: US COVID-19 mortality rate is 3.1%

by George J. Dance

Today, thanks to the internet, it is not hard to find information on COVID-19. However, given that anyone can post there, it is hard to find accurate information (or even information one can confidently believe); much of what one encounters is either unfactual, or while based on accurate data spun to imply inaccurate conclusions. To combat that, many websites have begun fact checking each others' stories; but in many cases, that has only served to further spread misinformation.

A case in point concerns a "Fact check" I read Friday in USA Today, "COVID-19 is deadlier than the 1918 Spanish flu and seasonal influenza." The article deals with a Facebook meme that makes what author Courtney Cox thinks is a misleading "comparison with the H1N1 pandemic of 1918 (the Spanish flu) and the seasonal flu." She accuses the meme creator of exaggerating the Spanish flu's death rate: while the meme claims a mortality rate of 5.6%, she writes, "an article in 2006 in the health journal Emerging Infectious Diseases, published by the CDC, cites a 2.5% global mortality rate." Meanwhile, the CDC (U.S. Center for Disease Control) has " reported that the annual mortality rate for the seasonal flu is about 0.01%,." In contrast, says Cox, "The COVID-19 mortality rate in the USA was 3.1% as of Thursday, according to Johns Hopkins University." (stress added)

A disease's mortality rate, or death rate (per Wikipedia), is "a measure of the number of deaths in a particular population, scaled to the size of that population, per unit of time. Mortality rate is typically expressed in units of deaths per 1,000 individuals per year; thus, a mortality rate of 9.5 (out of 1,000) in a population of 1,000 would mean 9.5 deaths per year in that entire population, or 0.95% out of the total." The population of the United States as of today, according to Worldometer, is 331,272,237. So a mortality rate of 3.1% would mean 10,269,439 dead Americans during the pandemic.

As of Friday, Worldometer is reporting 179,200 COVID-19 deaths in the USA, for a current mortality rate of just over 0.05%. Of course, that will not the be last word; the number of deaths, which has been increasing by over 1,000 per day, will keep rising in the future, and the mortality rate will rise along with it. All we can say right now, in the middle of the pandemic, is that the mortality rate over the pandemic's course will be higher than 0.05% – a point Cox marshalls in support of her 3.1% figure:

Though the number of people dead from COVID-19 as a percentage of world population at one point in time may be an accurate number, it is not reflective of the mortality rate of the virus. The mortality rate is not 1%, as the meme claims, but 3.1% in the USA, according to the latest data. That is far higher than seasonal flu and worse than the 1918 pandemic.

Yet the fact that more deaths are sure to come is no reason to believe that the COVID-19 mortality rate will ever reach 3.1%. COVID-19 deaths are rising, for sure; but at the current rate of increase (10,000 every nine days) it would take over 9,000 days – almost 25 years – for them to reach 3.1% of the population (and most likely not even by then, as the U.S. population likely would also have increased).

To support her claim, Cox cites a page on the Johns Hopkins University website, "Mortality analyses." That page gives a figure for current "deaths per 100,000" for the USA of 53.27 per 100,000 (again, just over 0.05%), but it also gives an "observed case fatality ratio" (CFR) for the country of 3.1 deaths per hundred, or 3.1%. That seems to be the only source for Ms. Cox's mortality rate claim. If everyone in the country becomes an observed case, and if the CFR stays at 3.1%, that would indeed equate to 10,269,000 or so deaths. However, there is no reason to think either of those ifs is going to happen. 

First, Cox ignores the concept of herd immunity. There is currently no scientific data on whether or not getting COVID-19 confers any immunity; nor can there be, given that the disease is so new. However, assuming that the disease is like every other known viral disease, one can expect those to recover to have at least short-term immunity. Given that assumption, calculating herd immunity is as easy as calculating the disease's initial reproduction number, or Ro. (The herd immunity threshhold is equal to (Ro-1)/Ro ).

Imperial College's infamous Report 9, the March report that frightened Britain and the USA into lockdowns, estimated an Ro of 2.4. Imperial's Report 12, issued in May, revised that number up substantially to 3.8. Using the higher number gives a herd immunity threshhold of 74% of the population, which alone would reduce the hypothetical mortality rate to 2.3% and possible deaths to 7,600,000. 

Second, there is no reason to think the CFR really measures the disease's lethality. There are many more people infected with COVID-19 than the number of observed cases. How many? According to Cox's own publication, "The real number of coronavirus cases is much higher than the recorded infections, according to a new study from the Centers for Disease Prevention and Control. The research, published Tuesday in the journal JAMA Internal Medicine, looked at antibodies in blood samples taken from 10 geographic regions. Researchers found a range from six to 24 times the number of documented cases, but most sites likely have 10 times more infections than reported." 

Calculating the mortality rate means multiplying not by the CFR – the ratio of observed cases who die – but by the infection fatality ratio (IFR): the ratio of people who get the disease who die. Fortunately, we do not have to look up the currently estimated IFR, since the number appears in Cox's own article: "According to the latest data available from the CDC, COVID-19 has an overall infection mortality ratio of 0.0065." Using that figure instead gives a mortality rate of 0.65% and a death toll of 2,153,270 (assuming no herd immunity) or, respectively, 0.48% and 1,593,420 (assuming herd immunity). Those figures still look shockingly high (by a factor of 2 to 4), but nowhere near as shocking as Cox's 3%+ estimate. 

Back on March 3, the world media reported, citing the World Health organization (WHO), that "the mortality rate for COVID-19 is 3.4% globally" – an alarmist claim that set off worldwide panic, with consequences we will have to deal with for years. That figure has been repeatedly debunked, and today even the WHO no longer stands by it. I was saddened to see the same type of alarmist claim coming back into circulation, especially in a "Fact check." COVID-19's alleged "3.1% mortality rate" is not a fact.