COVID-19 No "Worse" than The Flu?

It is very common these days for people with varying motivations to make the argument that that COVID-19 the current pandemic caused by the SARS-CoV-2 virus is no worse than seasonal influenza.  After presenting that premise, the conclusions are typically that there is really no reason to implement social distancing, stay at home orders, and all of the additional precautions currently in place to prevent the spread of the virus.

The important qualifier here is the need to include how deaths from both illnesses are estimated.  The CDC is very clear that it does not know the exact number of influenza deaths each year but it estimates them from statistical models. This is nothing new and they have been using this procedure for decades.  The reasons include the fact that influenza deaths are not reportable at a national level, although pediatric influenza deaths are.  It is also not possible to know if influenza is the proximate cause of death because the death may occur weeks later as a result of a secondary infection or an exacerbation of a chronic medical condition by the influenza infection.  In these cases, influenza may not be listed as a secondary infection.  Finally - not everyone who dies from an influenza-like illness (ILI) has influenza and not everyone who dies from ILI is tested for influenza. The influenza death estimates are not based on death certificates for that reason.  

There is considerable variability in mortality estimates based on the model being used.  A description of their current methodology and its limitations is available at this link.   There is a similar limitation of COVID-19 related deaths and the CDC has a specific reporting procedure suggested for that process.  CDC clinical criteria and lab testing is further specified to determine if COVID-19 is an underlying cause of death. COVID-19 can be reported as "probable" or "presumed" based on clinical judgment.  Three examples are given in the linked document in how to fill out the death certificate. The main difference is that COVID-19 mortality depends on deaths certificates and influenza mortality does not.  At least for now.

Looking at the CDC death rate estimates for influenza over time looks like this (click to enlarge any graphic):

But looking at the raw data based on death certificates looks like this:

Looking at the typical influenza season going from 2019 (week 43) to 2020 (week 15) shows that the raw death certificate data for pneumonia is 90,369 and for influenza it is 7,591.   


The argument typically is made looking at disease mortality and the raw number of deaths are not used. The CDC and other agencies report rates per 100,000 to correct for differences in population.  The current mortality rate for COVID-19 as of today is shown below - even though the lead graphic illustrates that deaths are continuing to increase at this point.:


COVID -19 Deaths  CDC Page

Total Deaths: 37,158

Death Rate/100,000: 11.3

First Case January 21,2020


Influenza Deaths

Total Deaths:  24,000 - 62,000  2020 estimate based on above data and methodology

Death Rate/100,000:  7.3 - 18.9

First Case October 2019


The second consideration is that the COVID-19 pandemic is clearly not over. Different geographic areas in the US are at different points in the curve that depicts new cases.  The key point on that curve is the inflection point where the new cases per day go from a linear increase to an exponential one.  A panel of 20 experts in infectious disease modeling was referenced as the source for a recent White House estimate of 240,000 deaths by the end of 2020 (8).  If you look at that reference there is a wide confidence interval.  That is four times the CDC estimate of 2020 influenza deaths.  For comparison there were 675,000 deaths in the USA in the 1918 pandemic.

How does this information assist with the analysis of rhetoric?

1.  COVID-19 is no worse than seasonal flu: 

First off, influenza is a severe infection and can't be trivialized. Everyone who is able to should get an influenza vaccination. Based on the available data - is certainly seems that COVID-19 is as bad and much worse in the worst case scenario.  It is at least on par with modern CDC influenza death rates estimates over the past 20 years and based on the current number of deaths is likely to exceed the 2020 estimate for influenza deaths.  The outliers for the White House estimate in the survey are much higher - in some cases exceeding the mortality from the 1918 pandemic.  These estimates are also based on current rates and if the country is "opened" and stay-at-home orders, wearing masks and social distancing guidelines are abandoned it is very likely that there will be secondary spikes and prolonged exposure to the virus. Does anyone really want to take the chance of this virus killing more people than the 1918 pandemic?  

2.  COVID-19 rates are inflated based on inaccurate reporting:

This meme was reinforced by a physician appearing on a conservative talk show who stated that he only reports what he considers to be the underlying cause of death on death certificates.  The example given was that if the patient died of pneumonia - the cause of death was pneumonia and would not speculate on what caused the pneumonia.  The implication being that death certificates are highly accurate and the suggested reporting guidelines for COVID-19 will result in over-reporting the condition.  The information clearly shows that this is not the case. The actual numbers of deaths due to influenza as reported on death certificates are a fraction of the number estimated by the CDC.  The CDC plainly states that they have no idea how many people actually die from influenza and for decades they have estimated the number based on hospitalizations, hospital mortality, and other surveillance numbers.  COVID-19 death counts are made on the basis of death certificates.  Even though death certificates are not perfect, it is likely that many more people who die from COVID-19 are tested than people who die from influenza. It will be interesting to see if the CDC develops statistical models for COVID-19 to see if the current deaths are an underestimate like influenza. 

That is my brief look at these two arguments that are being used to suggest that the current environmental approach to virus containment are unnecessary.  I am also reminded of an old statistical concept called face validity.  Briefly stated that would mean the null hypothesis of no difference in death rates makes sense.  Given that COVID-19 has risen to the highest daily cause of death in the US, that hospital and ICU beds in many locations are overwhelmed, that there is a catastrophe in New York City at this point, and it has led to the only mass shortage of personal protective equipment, ventilators, and medical gear that I can recall in my 3 decade career - I don't think that it does make sense.

And this is exactly not the time to trivialize this pandemic.


George Dawson, MD, DFAPA


References:

1: CDC:  Frequently Asked Questions about Estimated Flu Burden.  Link

2: CDC:  Estimating Influenza-Related Deaths.  Link

3: National Center for Health Statistics. Guidance for certifying deaths due to COVID–19. Hyattsville, MD. 2020. Link

4: Reed C, Chaves SS, Daily Kirley P, Emerson R, Aragon D, Hancock EB, et al. Estimating influenza disease burden from population-based surveillance data in the United States. PLoS One. 2015;10(3):e0118369

5: Rolfes, MA, Foppa, IM, Garg, S, et al. Annual estimates of the burden of seasonal influenza in the United States: A tool for strengthening influenza surveillance and preparedness. Influenza Other Respi Viruses. 2018; 12: 132– 137. https://doi.org/10.1111/irv.12486

6: Centers for Disease Control and Prevention. Estimated influenza illnesses and hospitalizations averted by influenza vaccination – United States, 2012-13 influenza season. MMWR Morb Mortal Wkly Rep. 2013 Dec 13;62(49):997-1000.

7: Reed C, Kim IK, Singleton JA, Chaves SS, Flannery B, Finelli L, et al. Estimated influenza illnesses and hospitalizations averted by vaccination–United States, 2013-14 influenza season. MMWR Morb Mortal Wkly Rep. 2014 Dec 12;63(49):1151-4.

8:  Thomas McAndrew Spring March 25, 2020 COVID19-Expert ForecastSurvey6-20200325.pdf 


Graphics credit:

Lead graphic is from Our World in Data licensed under Creative Commons BY-SA and may be freely used for any purpose. 

All others are from the CDC under public domain.