Do Not Compare COVID-19 (Coronavirus) To Seasonal Influenza

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42pines specializes in Occupational Health; Adult ICU.

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Do You Think COVID-19 and Seasonal Influenza Compare?

Increased awareness and preparation in schools about Covid-19

Covid-19 should not be compared to seasonal Influenza

It’s normal to look at the CFR (case fatality rate) of seasonal influenza when considering Covid-19.  After all, 20-45 million get “the flu” every year.  The numbers vary depending on the year.  The “low” was the 2011-2012 season with 9.3 million cases and 12,000 deaths and the high was the 2017-2018 season with 45 million cases and 61,000 deaths.1

Let us look at the worst of eight recent flu seasons.  The CFR for that was 0.0014 meaning, 1.4 persons died per 1000 cases.  Interestingly, if we look at the “best” of the past eight seasons (the “good” one) the CFR is 0.0013, almost the same number of deaths per thousand cases.

So, hold on to this thought...

Seasonal influenza’s average risk of dying is about one death per 750 cases.

I see and hear CFR for the Covid-19 repeatedly being quoted at around 2-3%.  CFR currently (as of 2/27 12:23AM EST) is 3.4%.  That is 2,810 deaths divided by 82,550 cases.

But to say that the CFR for Covid-19 is 3.4% is not wise.  Why?  Simply put, the CFR is not applicable are even a number that one can calculate since it's a "look-back" number.

CFR is a “look-back” rate

It is very useful when we look back to an epidemic/pandemic that has ended.  For instance, when comparing the “good” 2011-2012 flu season to this season’s numbers.  CFR is death rate / # of confirmed cases.  To divide the known number of cases today by the number of deaths, we get 3.4%.  But this is not wise to use because it assumes that ALL of the remaining cases (total cases today of 82,550, minus cases where the person has recovered or died) will be cured.  This is “magical thinking.”  Many of those remaining 46,488 will recover, but some will die.

In short, we won’t know the true CFR for another year or more.  CFR is useless at this time, it will be helpful sometime next year.

Known outcomes

So, let us look at the cases with known outcomes, meaning the sum of the cases of those who have recovered plus those who have died.  This population is composed of those 33,252 who have, to today, recovered plus the 2,810 who have died; thus, our population is 36,062.  If we divide 2,810 (deaths) into our population of 33,252, we find an overall death rate of 8.45% or about 85 per one thousand cases with known outcome.

Please let that sink in for a bit.  Today, looking at Covid-19 cases with known outcomes, 85 out of 1000 cases have died.

Should this hold, and it may, then 1 out of 12 cases will die.

Compare this to seasonal influenza where 1 out of 750 cases will die.

The death rate currently for Covid-19 is 62x the death rate of the average seasonal influenza.

These two illnesses do not compare, although we’ll really not know for a year or so, at which time we can look back to see what the true CFR rate was.

Let us look now at areas/countries to see the current death rate is, of those cases with known outcomes.

I’ll call the current fatality rate of known outcome cases: CFR-KO.

I shall call the population with known outcomes: PWKO

Total deaths / PWKO = CFR-KO or current death rate.

• World: 2801 / 36,062 = 8.45% or ~85 deaths per 1000 cases.
• Hubei Province: 2641 / 26,024 = 10% or ~100 deaths per 1000 cases.
• South Korea: 13/35 = ~37.2% or 372 deaths per 1000 cases.
• Italy: 14/54 = ~26% or 260 deaths per 1000 cases.

We see that regional epidemic outbreaks tend to drop in CFR-KO as time goes by.  Whether the true “look-back” CFR will drop to 2 or 3% or some other number (lesser or higher) depends on many factors which are simply unknown.  For instance, children appear to be much less at risk for Covid-19, and cases within Africa (other than the one in Egypt) seem oddly absent.  Perhaps the virus does not do well in warmer climates.  Perhaps the fatality rate will drop as we approach Summer in the Northern hemisphere—we do not know.

Perhaps the tendency of the media to quote the 2-3% theoretical CFR comes from the fairly recent 2009 H1N1 flu pandemic.  The 2009 “swine” flu was very feared.  It infected 10-200 million world-wide with estimates of death ranging from 105,700 to 395,600 and a CFR of 0.03% or 3%.  (30 per 1,000 cases). (Wikipedia).  It was expected to return far, far worse numbers.

The “swine” flu, which was the first pandemic of this century, turned out to be far less lethal than many expected.  Triggle wrote in an article from December 10, 2009 titled, Swine flu less lethal than feared, "The swine flu pandemic is ‘considerably less lethal’ than feared, chief medical officer Sir Liam Donaldson says,” adding, “A study led by Sir Liam found a death rate of just 0.026% in those infected, the British Medical Journal reported.”2

Will we be lucky?

Perhaps we’ll be lucky this time, too, although I suspect we won’t be as lucky as we were for the “swine flu.”

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Nurse SMS has 9 years experience as a MSN, RN and specializes in Critical Care; Cardiac; Professional Development.

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Timely and well outlined. I do wonder, though, at the "known cases" portion of the equation. With the limitations of available testing and the likelihood that many are infected and only get a mild case or even no symptoms, these mortality numbers may be skewed high.

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What are you thoughts on this?

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I know this is a rapidly evolving story but your numbers are already so far off. As of today Italy reports 2,000 cases and 50 deaths. That’s a long way from a 25% death rate.

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“Being an infectious diseases physician, research microbiologist, and former deputy commander of the Walter Reed Army Institute of Research (which is in the business of identifying, researching, and mitigating infectious disease threats), I thought I’d make a few comments about Coronavirus Disease-2019.

Firstly, we've known about coronaviruses since the 1960s. Named for the crown-like arrangement of glycoproteins on their capsid, the coronaviruses comprise a family within the order Nidovirales and consist of four genera: alpha, beta, gamma, and delta. Coronaviruses are common in birds and mammals (with the greatest diversity in bats), and human infections are caused by two alpha- (I.e. HCoV-229E and HCoV-NL63) and several beta- (e.g. HCoV-OC43 and HCoV-HKU1) species. Severe Acute Respiratory Syndrome coronavirus (SARS) and Middle East Respiratory Syndrome coronavirus (MERS) are also beta-coronaviruses. Coronaviruses are ubiquitous and along with rhinoviruses, parainfluenza, metapneumovirus, and respiratory syncytial virus, cause most community-acquired upper respiratory tract infections (I.e. the common cold).  As with other respiratory viruses, coronaviruses occasionally cause more severe illness. Individuals at the extremes of age (I.e. infants and the elderly), as well as those with comorbid pulmonary disease (e.g. chronic obstructive pulmonary disease), or immune compromising conditions (e.g. hematopoietic stem cell transplant or HIV infection) are at increased risk. Certain coronavirus species (e.g. HCoV-OC43, SARS-CoV, and MERS-CoV) also are associated with more severe infection. Except for SARS-CoV and MERS-CoV, there has not been much interest in producing coronavirus vaccines. This derives from the fact that most coronaviruses: 1) cause mild, self-limiting illness; 2) are difficult to replicate in tissue culture; 3) display antigenic variation (That is to say that the surface proteins against which protective antibodies would be made change); and 4) Vaccine trials with at least one animal coronavirus demonstrated a worse outcome upon challenge with the virus (a problem similarly posed by dengue virus). Although some medicines, including antivirals and chloroquine, have demonstrated potent in vitro antiviral activity against tested coronaviruses (I.e. SARS-CoV, HCoV-229E, and HCoV-OC43), there are no clinical trials assessing efficacy and treatment is supportive.  As with other respiratory viruses (such as rhinoviruses), coronaviruses are transmitted by respiratory aerosol, and the mainstay of prevention is handwashing, respiratory hygiene (I.e. covering the cough or sneeze), and disinfection of fomites (I.e. inanimate objects which can become contaminated).

The coronavirus now in the news emerged in late 2019 as a novel variant out of Wuhan, a city in the Hubei Province of China—hence, its earlier designation 2019-NCoV (I.e. 2019 Novel Coronavirus). Since it is no longer novel and is genetically and clinically like SARS, 2019-NCoV was re-designated SARS-CoV-2. SARS-CoV-2 has subsequently spread to other countries including South Korea, Italy, Iran, and Japan. Most cases have been among people who had either traveled from China or who had been exposed to someone known to be infected with SARS-CoV-2. However, several cases in the United States were recently diagnosed among people with no obvious risk factors, suggesting that community transmission is occurring. The incubation period for SARS-CoV-2 appears to average 3-6 days. Because viral DNA has been isolated from respiratory secretions of exposed asymptomatic individuals, it is believed that not everyone who is exposed will become ill. The extent to which these individuals transmit SARS-CoV-2 to others is not yet known. Epidemiological studies of the Wuhan outbreak suggest that most infected individuals will have mild disease (81%), and only a minority will develop pneumonia (14%) or pneumonia with respiratory failure, shock, or multiorgan dysfunction (5%).The overall estimated case fatality rate (CFR) appears to be ~2.3%, making it less deadly than some influenza strains and far less deadly than MERS. Moreover, the CFR was lower outside of Wuhan (0.7%) and as with other coronaviruses, risk factors for severe or critical disease include extremes of age, comorbid illness, and immune compromising conditions.

SARS-CoV-2 RNA detection is by means of polymerase chain reaction (PCR) amplification, using an assay that is currently only available (in the you.S.) at the Centers for Disease Control and CDC-qualified labs. However, there is a push to make the assay more available (e.g. to state health labs). Currently, the treatment of individuals infected with SARS-CoV-2 is supportive, but antiviral drugs including nucleotide analogues and protease inhibitors are being studied. As with other coronaviruses, the mainstay of prevention is handwashing, respiratory hygiene, and disinfection of fomites. Several labs, both in the you.S. and in Israel, are pursuing a SARS-CoV-2 vaccine, buoyed by the stability of at least some of the spike glycoproteins as well as sequence homology with several other human and poultry coronaviruses. It is also possible that as more and more people become exposed to SARS-CoV-2 and develop protective antibodies, transmission between susceptible individuals will decline (the “herd effect”).

Although the emergence of a novel pathogen is never a trifling matter, it is important for people to have a realistic understanding of the disease caused by it without succumbing to hysteria. To date, SARS-CoV-2 has shown itself to be a respiratory viral pathogen most commonly causing mild, self-limiting illness, with more severe disease limited to certain susceptible populations (in contrast, say, to the 1918 H1N1 influenza virus which disproportionately killed healthy younger people). Moreover, researchers are making progress in developing vaccines and therapeutics. I certainly don’t mean to trivialize SARS-CoV-2. However, I've seen far more lethal viral pathogens such as HIV, rabies, Ebola, and other viral hemorrhagic fever viruses; and unless something changes with the virus, I am only moderately alarmed by SARS-CoV-2.

On a positive note, the anti-vaxxers suddenly seem awfully quiet on social media…”

Author is Dr. Michael Zapor

Edited by Wuzzie

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myoglobin has 12 years experience as a ASN, BSN, MSN and specializes in ICU, trauma, neuro.

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I believe that the above analysis may overstate the fatality rate. Consider Johns Hopkins figures that are updated daily

They report (as of March 02 at 2:50PM Pacific, 2020) that there have been a total of 90,305 cases worldwide with 3085 deaths.  This would equate to a case fatality rate of around 3.41%.  For South Korea the numbers are 4335 cases with 28 dead or a fatality rate of 0.65% percent. For Italy the numbers are 2036 infected with 52 dead or 2.6%.  While these numbers are higher than seasonal influenza they are much lower than the numbers expressed in the article. Also unlike the say the 1918 Pandemic which preferentially killed the young and healthy covid 19 seems to have a mortality pattern primarily killing older patients especially those with co-morbid conditions (much like seasonal influenza). Of course it is worth noting that the 1918 pandemic largely "went away" in the Spring only to return with a vengeance in the Fall. However, I believe that perhaps an even greater danger from Covid 19 than it's absolute health effects is the disruption in supply chain and ramifications that it may create for "human behavior".  It may have economic ramifications that far out weight its direct physiological consequences and these could indirectly lead to greater morbidity and mortality.  For example how many people in areas under quarantine in China who have medical issues such as needing dialysis or insulin will die due to the inability to get needed medical attention?  If people "hoard" supplies in the United States will this lead to homeless shelters having less "left over" food supplies to distribute to people in need?  Will people stay home from doctors appointments or avoid going to the hospital for "regular influenza" for fear of Covid-19 and therefore suffer greater morbidity?  Will an economic downturn (from worldwide disruptions) create economic hardships that lead to a host of issues that put those "on the edge" or in poverty at greater risk?  In these ways and others this disease may cause unprecedented devastation.

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myoglobin has 12 years experience as a ASN, BSN, MSN and specializes in ICU, trauma, neuro.

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Then again the same site that I reference above lists six deaths for the United States (all in the greater Seattle area where I am) and seven recovered. Thus, if that were the actual number infected (and it is probably much, much higher since most people will not demonstrate symptoms, or will presume they have a cold) we would be hovering at a death rate of around 47% in the King county area.  I'm thinking that my Airbnb landlords should be giving me a discount since I doubt to many tourists will be heading here on vacation anytime soon.

Edited by myoglobin

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42pines specializes in Occupational Health; Adult ICU.

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On 3/2/2020 at 10:13 AM, Nurse SMS said:

Timely and well outlined. I do wonder, though, at the "known cases" portion of the equation. With the limitations of available testing and the likelihood that many are infected and only get a mild case or even no symptoms, these mortality numbers may be skewed high.﻿

Nurse SMS, you are correct in saying "these mortality numbers may be skewed high."  This is an important point.

There is so much undefined, for instance, cases emerge with no symptoms or little symptoms, combined with statements indicating that these cases shed virus.  This is a unique factor that likely will increase the spread of cases.

Those with mild cases, that show little or no symptoms, when eventually added to the CFR will indeed lower that rate, and will lower any fatality rate.

Often, countries that are "new to virus," will show inordinately high fatality rate.  South Korea, Iran and Italy falls into this category, often near 45% which is where the early stages of the virus in Wuhan was.  As time goes by, the fatality rate appears to fall, perhaps as cases with less severe symptoms or co-morbidity appear.

The fatality "rate" is often skewed high and, over time, is likely to drop.  The "mortality numbers," is an unknown factor that depends, as does the seasonal influenza, on just how many become ill.

On 3/2/2020 at 12:43 PM, Wuzzie said:

What are you thoughts on this?

Sorry, I closed my facebook account long ago after facebook "opted me" into one of their policies what I felt invasive.  Therefore, I cannot see anything other than Zapor's bio.

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16 minutes ago, 42pines said:

Sorry, I closed my facebook account long ago after facebook "opted me" into one of their policies what I felt invasive.  Therefore, I cannot see anything other than Zapor's bio.

I copied and pasted the post in it's entirety about 2 posts down from my original. In fact it's just two posts up from the quoted response.

Edited by Wuzzie

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42pines specializes in Occupational Health; Adult ICU.

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On 3/2/2020 at 1:50 PM, CommunityRNBSN said:

I know this is a rapidly evolving story but your numbers are already so far off. As of today Italy reports 2,000 cases and 50 deaths. That’s a long way from a 25% death rate.

This was written eight days ago, submitted, but not posted as an article right away.  I did make a more timely post that's the equivalent of this in "News."

Any article on this subject becomes "dated," almost immediately.  When I posted this Italy was a tiny "blip" on the virus map, now it is the fourth largest "blip."

Let's look at Italy's number's today (3/4 10:18AM)

2502 confirmed cases; 79 deaths and 160 recovered.

There is an "urge" time simply divide deaths by confirmed cases: 79/2502=3.1%, this is the CFR (Case fatality rate).

Yet this number is completely meaningless, and here's why:  Look at cases with "known outcomes" meaning that those afflicted have either died or recovered.

This population is the sum of those who have died + those recovered = 239

Of this population of cases with "known outcome" 79/239 = 33% death rate.

We do not know what will happen to most of the 2502 cases, but we do know that neither all will die, nor all will recover, with no deaths.  This is why we cannot divide deaths/total cases..

Italy now:  Current death rate of cases with known outcomes / 33%

You are correct, currently Italy is a "long way away from a 25% death rate," however it's actually in the direction opposite that you imply.

Over time, predictably, as cases with lesser severity appear, this number will likely fall.

To sum this up:  It is inappropriate to simply divide deaths by total confirmed cases.  It is more appropriate to divide deaths by the population whose outcome has been defined as dead or survived.

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19 minutes ago, 42pines said:

To sum this up:  It is inappropriate to simply divide deaths by total confirmed cases.  It is more appropriate to divide deaths by the population whose outcome has been defined as dead or survived.

Please explain why your way is more appropriate given that the calculation you are using does not include the entire affected population only the eported outcomes? No snark intended but your numbers seem artificially high and given that this is a public forum I have serious concerns that without absolute confirmation that the death rates you are calculating are accurate this entire thread may be contributing to the panic we are seeing occur.

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The WHO has adjusted the CFR to 3+