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An Honest Question About Flu Numbers
One of the few pieces of good news this year is that the flu season has been exceptionally mild so far. While it’s great that we don’t have to face two deadly epidemics simultaneously, I have a question:
Why is there less flu in 2020 than other years?
Here are the possibilities that I have come up with:
- Everyone who was going to get the flu has already succumbed to the Wuhan virus.
- The preventative measures being used to fight the Wuhan virus protect against the flu.
- More people are getting flu vaccinations and/or the vaccines are more effective than other years.
- Flu cases are being undercounted.
- Exposure to the Wuhan virus in some way provides protection from the flu.
- The flu strain is extraordinarily mild this year,
The impetus for this post was a discussion I had with @kozak in the comments of @arizonapatriot‘s excellent post, Covid Deaths Are Real: Rebutting Dr. Briand. I stated that I thought that the reason that there are fewer flu deaths was because most of the people who were going to die of flu were already dead from the Wuhan virus. Kozak replied:
We have tens of millions of elderly and people with multiple risk factors for covid death who are 50+ years old. Plenty of people left to potentially get infected and die either of Covid or the flu. . .
Only a tiny fraction of those susceptible have died. Again. tens of millions of elderly, hypertensive, diabetic, cardiac, immunocompromised, fat, etc etc etc people in the US.
It is true that only a tiny fraction of those susceptible die of the Wuhan virus, but the same can be said for people who die of flu. While there are millions at risk, only the most susceptible die of either disease. I would bet the Venn diagrams of both populations are pretty congruent.
Still, while that may be a partial answer to why fewer people are dying, it doesn’t answer why fewer people are contracting the flu.
Kozak and others have posited that people are not getting the flu because of the protective measures: hand-washing, masks, distancing, lockdowns, etc-being used to stop the spread of the Wuhan virus. That begs the question: If these measures are stopping the spread of the flu, why aren’t they working to stop the spread of the Wuhan Virus? Right now, cases of the Wuhan virus are supposedly “surging” throughout the country, despite the fact that the protective measures have been in place for months. Why isn’t flu surging as well? Stating that the Wuhan virus spread is from people being careless about wearing masks is not an answer, because the flu should also be affected by how well the rules are being followed.
I’m posting this because I’m honestly puzzled about it. It could be the possibilities listed above are all, to one degree or another, reasons we are seeing less flu. What do you think?
Published in Healthcare
I too have been curious about this. I found this interesting article from the American Society for Microbiology: “COVID-19 and the Flu.” I’ve been wondering if the two viruses are competing with each other. According to this article, that may indeed be the case and partly explain the low flu numbers:
We will find out in roughly 32 days what the total number of deaths were in the United States in 2020, and how that compares with 2019 and previous years, both with and without major flu outbreaks. The suspicion is while the mortality rate in ’20 may be up from ’19, it’s not going to be up to the level that merited the hype back in the spring, or the renewed media freak-out, where the tone of the reports treats COVID as a death sentence, but where coronavirus has been given the priority over other comorbidities, where cause of death which in 2019 would have been attributed to those ailments instead were transferred over to COVID, in order to ‘convince’ the public to do the right thing.
Thank you, Jose. I think more discussion of this kind of thing would be useful.
One of the things I’ve wondered about (and mentioned elsewhere) is the effect of telemedicine on flu diagnoses. In prior years, I assume people tended to go to the doctor, get tested and diagnosed, and so get counted as an influenza instance. I’m guessing that that doesn’t happen with telemedicine, and that instead people are diagnosed remotely, told to go to bed, and neither tested nor counted.
Of course, it could be that most people who have a remote session with a medical professional and who present flu-like symptoms are told to get tested for COVID. If that’s the case, I wonder what happens if their COVID test turns out negative. Do they then go to a medical clinic and get tested again, this time for influenza?
Given that, as I understand it, the actual annual influenza count is post-modeled each year from rather limited testing data, I can imagine how anything that disrupts the normal influenza testing process might be magnified in the modeled influenza count.
In a typical flu season, Nov – May, about 30 to 60 million people get the flu in US.
How many ‘cases’ of covid?
Flu deaths are definitely being undercounted
Flu cases are not counted in the same way as Covid. With covid the U.S., and other countries, count actual test results on a daily basis. Flu case estimates are developed after the fact, based on modeling. Individual cases are not reported during the season, with the exception of deaths of children which are required to be reported by the CDC (for reasons described at the end of this comment).
Estimates during flu season tend to be qualitative, not quantitative, though individual hospitals or health systems may develop specific numbers.
The closest real-time flu estimates are via the CDC’s Hospital Influenza-like-illness (ILI) Surveillance data in which the % of both inpatient visits and ED visits in which the patient exhibits ILI type symptoms are reported. For instance, in AZ last week 2.3% of ED visits and 1.6% of inpatient visits were reported as ILI. During the 2019-20 flu season this was much higher before dropping off when covid showed up. In early March 2020, 8.7% of ED visits were ILI and 3.3% of inpatient.
The CDC has instituted a similar system for covid designated CLI. Last week in AZ 7.3% of ED visits and 11.3% of inpatient visits were CLI.
I do not know how clinicians are distinguishing ILI from CLI.
One other thing to note on the difference between covid and flu. Covid seems to have very little impact on children, while flu is more deadly, particularly for very young children.
The Magic of Masks ;)
Flu cases are counted accurately
Covid ‘cases’ are inflated
So we should open schools for covid and close schools for flu?
Perhaps flu cases are being reported as Covid-19. False positives and all that.
We keep looking, we just aren’t finding it. Pretty much anyone who comes in to be checked with flu like symptoms is getting screened for both covid and flu. We are finding very few flu cases.
I suspect some combination of reasons mentioned above ( except for “all the susceptible are dead”. Thats just insane.)
Weak strain, good vaccine, and the masks and distance and hygiene for covid are making it difficult for flu to compete.
Where were the masks last year?? Why don’t we wear masks everywhere and at all times for the rest of our lives? Then we can eradicate all viruses.
Covid is more contagious than the flu. It spreads easier.
There is also a difference in the incubation period. For the flu it is 1-4 days for Covid it is 2-14 days. This difference means that more people spread the virus before they have symptoms. With the flu you get sick quicker and stay away from others quicker.
Thanks. You are the first to give a coherent answer.
I work in a children hospital ER. We have seen zero cases of flu this season. Patients presenting with medical problems are down in general. Our patient population is half of what we see normally, and the majority are injuries of some sort. Also, since this started, I have only seen about a dozen positive Wuhan virus cases out of the hundreds I’ve taken care of. Only one was symptomatic at the time of their ER visit.
Flu hygiene.
This causes me to worry politicians everywhere will use the “success” of their restrictions to impose them on an annual basis – at first. It wouldn’t surprise me to see them go for year-round control of our “safety” under the guise of public health . . .
Could it be that the regular flu is the reason for so many false positives? Is it possible that a lot of these people test positive for Covid but actually have regular flu, stay home, get over it, and go on their merry way. Not everyone with Covid or any other flu winds up in the hospital.
I would be surprised, because (as I understand it) influenza is not caused by a coronavirus, but rather by influenza viruses. On the other hand, the common cold is often caused by a coronavirus, and it wouldn’t surprise me if there were some false positives triggered by past exposure to a cold.
It also seems plausible that past coronavirus (cold) exposure may have conferred T-cell immunity to many of us. Perhaps we are fortunate that we never cured the common cold. ;)
The reason I started to question the testing results is that last week some friends of my son were supposed to come to his house for Thanksgiving and could not because one in their family was sick and tested positive for Corona. The entire family (5 of them) went for testing, quarantined and also got sick a couple days later. Of the five family members only one tested positive for Covid yet they all pretty much had the same symptoms. Is that not odd?
When trying to differentiate between covid and flu symptoms what are the indicators you look for?
Odd? Yes. Exceptional? I don’t know. ;)
I would appreciate more transparency in the public conversation about: (a) the kinds (technologies) of COVID tests being performed; (b) the CT values used in the PCR tests; and (c) the false positive and false negative rates for each kind of test.
The media practice of quoting the scariest number, whatever that happens to be, is tiresome.
Because last year we lost about 30k to the flu, a typical bad flu year, not 10 times that number. We can’t eradicate all viruses, not all are respiratory. But yeah if we wore masks ( like they have been doing in Asia forever) we could cut down the numbers.
A lot of it has to do with the timing of the testing in the individual. Also with the technique of the person getting the sample.
That’s interesting. Thank you.
I’ve read that there are different immunological responses — primarily T-cell and antibody — and that an infection suppressed by a T-cell response might not result in the presence of antibodies. Is that plausible, or did I perhaps misunderstand what I was reading?
If that’s true, are infections suppressed by a T-cell response typically or necessarily experienced differently, in terms of symptoms, than those suppressed by an antibody response?
That is not tru the data is by flu season. The flu season is not a calander year. It ends in the summer. So we already have a good idea. Although there will be revions as the data is more sanitized. When you read historical data ita based on a flu season not jan thru dec year. Now from an overall morality rate. You are correct. So the 19/20 flu season was already really bad without COVID. Maybe in the last 20 years second worse. However with an aging population. I think we can expect to have a lot worse flu Seasons for the next two or three decades. We dont know yet if in Jan Feb we wiil have a similar trend to that of the south hemisphere.
I think the preventive measures against Covid have reduced the spread of the common flu. As to reducing or not reducing Covid, how do you know it hasn’t? How do you know how widespread it would be without these measures? I think it has.
Counterfactuals are always difficult.
But you invite the question: when you write “reduce the spread,” does that mean “reduce the ultimate number who will be infected,” or does it mean “flattening the infection curve?”
Since I don’t think it’s likely that we will end the widespread presence of the virus in the population any time soon, I think we should end lockdowns and allow as many of us as possible to resume living as normally as possible.
If masks ‘saves lives’ shouldn’t this ‘pandemic’ ended sooner?
14 days seems high
I thought it was 5 days, maybe 10
YES!
Why are kids ‘immune’ to covid? T cell immunity?