With all of the bad news across the world regarding the COVID-19 pandemic, the one tiny bit of good news is the substantial drop in influenza incidence during the 2020-21 flu season. Despite the weird and unfounded myths from the anti-vaccine and COVID-19 denier crowds, there is no conspiracy that someone is hiding the flu numbers by boosting COVID-19 numbers.
The only reason why the influenza incidence has dropped precipitously is because of the public health strategies to contain COVID-19. That’s it – nothing deeper than that.
2020-21 flu season so far
These two images of the flu season as of week 3 in 2020-21 vs 2019-2020 flu seasons show dramatically how different things are.
For the week ending January 18, 2020 (just a couple of months before the start of the COVID-19 pandemic) most of the USA had either “High” or “Very High” levels of influenza-like illness (ILI). For the week ending January 25, 2021, all states have minimal levels of ILI except for Oklahoma, which has a moderate level. I could find no explanation for the higher level in Oklahoma other than it is a more conservative state and hasn’t exactly been at the forefront of public health initiatives.
This is a graph of the percentage of patients who present with ILI to healthcare centers:
As you can see, the 2020-21 flu season is showing nearly the lowest percentage of visits for the past 8 years except for potentially 2011-12. In fact, the percentage of ILI visits is almost at the level that is predicted for the “off-season” for influenza, such as the summer.
Amazingly, there has been just one reported pediatric death from the flu during the 2020-21 flu season, compared to the usual approximately 200 annual pediatric flu deaths.
Now, as I have written frequently, correlation is not necessarily equivalent to causation. There could be a lot of reasons for these influenza incidence observations that have nothing to do with COVID-19 directly, so we should interpret it with caution:
- the COVID-19 pandemic has influenced to varying extents health-seeking behaviors – many people are not going to the hospital fearing that it puts them at risk of COVID-19
- the staffing of hospitals may have diverted resources from identifying and treating ILI.
However, the World Health Organization (WHO) recently published a report that showed that other areas of the world had much lower levels of influenza:
- In the Southern Hemisphere, countries observed influenza levels during their winter that was approximately equivalent to inter-seasonal (their summer) levels.
- In the Northern Hemisphere, influenza activity has been below inter-seasonal levels observed during the past few years.
- Other specific areas, such as tropical South America, tropical Africa, southern Asia, and Southeast Asia reported low or even no flu activity.
Additionally, the CDC states that:
Based on NCHS mortality surveillance data available on January 28, 2021, 14.8% of the deaths that occurred during the week ending January 23, 2021 (week 3), were due to pneumonia, influenza, and COVID-19 (PIC). This percentage is above the epidemic threshold of 7.1% for week 3. Among the 3,043 PIC deaths reported for this week (week 3), 2,102 had COVID-19 listed as an underlying or contributing cause of death on the death certificate and seven listed influenza, indicating that the current increase in PIC mortality is due primarily to COVID-19 and not influenza.
The drop in influenza activity seems to be closely related to many of the recommendations by public health authorities across the world – wash your hands, wear a face mask, and maintain physical distance from strangers.
Because COVID-19 and influenza transmission routes are fairly similar, it is plausible that all of the public health efforts with COVID-19 has vastly reduced flu activity. In fact, CDC researchers, in a peer-reviewed article, concluded:
Following widespread adoption of community mitigation measures to reduce transmission of SARS-CoV-2, the virus that causes COVID-19, the percentage of U.S. respiratory specimens submitted for influenza testing that tested positive decreased from >20% to 2.3% and has remained at historically low interseasonal levels (0.2% versus 1–2%). Data from Southern Hemisphere countries also indicate little influenza activity.
What are the implications for public health practice?
Interventions aimed against SARS-CoV-2 transmission, plus influenza vaccination, could substantially reduce influenza incidence and impact in the 2020–21 Northern Hemisphere season. Some mitigation measures might have a role in reducing transmission in future influenza seasons.
I think that it’s pretty clear that there is a strong correlation between our public health activities with COVID-19 and the reduction in influenza activity across the world. But that doesn’t stop the vaccine and COVID-19 deniers from dismissing this with their weird conspiracy theories.
Debunking the COVID-19 and influenza activity myths
So, let me just debunk a few of the biggest myths pushed by the pseudoscience-loving crowd regarding this reduction in influenza activity. I won’t link to any websites, because I am loathed to give them any clicks from here.
- Hospitals aren’t testing for the flu. Wrong. In fact, incoming patients that present with respiratory illnesses are tested for both COVID-19 and influenza, because the best treatments for each disease are different. Furthermore, if a patient presents with both the flu and COVID-19, that is a serious medical problem.
- COVID-19 is just the flu. Wrong. The influenza virus is in the phylum Negarnaviricota, while the SARS-CoV-2 virus, which causes COVID-19, is in the phylum Pisuviricota. They are as closely related as humans are to lobsters.
- There is a vast conspiracy where all patients with flu are counted as COVID-19 patients. Wrong. There is simply no evidence of this, and in fact, hospitals are reporting negative influenza tests.
I think there is plenty of solid evidence from scientific research that establishes that dealing with the COVID-19 pandemic has crushed the normal influenza activity across the world. In fact, it makes me think that I might wear a mask every winter even if we end this pandemic (and I’m not at all confident that we will any time soon, even if we really get vaccinations going across the world).
That being said, we should all get the flu vaccine just in case the flu decides to start up late. And the flu vaccine is safe and effective unless you have some deranged beliefs about it.
So, if you’re looking for one tiny silver-lining for this awful, deadly pandemic, the massive reduction in flu cases is one. Sadly, instead of an average of 389,000 dying of the flu every year worldwide, over 2 million people have died of COVID-19 worldwide. Not much of a silver lining.
- Olsen SJ, Azziz-Baumgartner E, Budd AP, Brammer L, Sullivan S, Pineda RF, Cohen C, Fry AM. Decreased Influenza Activity During the COVID-19 Pandemic – United States, Australia, Chile, and South Africa, 2020. MMWR Morb Mortal Wkly Rep. 2020 Sep 18;69(37):1305-1309. doi: 10.15585/mmwr.mm6937a6. PMID: 32941415; PMCID: PMC7498167.
- Paget J, Spreeuwenberg P, Charu V, Taylor RJ, Iuliano AD, Bresee J, Simonsen L, Viboud C; Global Seasonal Influenza-associated Mortality Collaborator Network and GLaMOR Collaborating Teams*. Global mortality associated with seasonal influenza epidemics: New burden estimates and predictors from the GLaMOR Project. J Glob Health. 2019 Dec;9(2):020421. doi: 10.7189/jogh.09.020421. PMID: 31673337; PMCID: PMC6815659.