Where has the flu gone?
by Pinedale Online!
September 19, 2021
One of the interesting outcomes of the COVID-19 pandemic are reports that the regular flu appears to have mostly disappeared for over a year now. In a typical year from 12,000 to 60,000 adults die due to the flu. Hospitals get flooded annually with flu patients. Up to 150 children die in the US from the flu each year. During the 2019–20 flu season—basically fall and winter, peaking in December, January, and February—18 million people in the US saw a doctor for their symptoms, and 400,000 had to be hospitalized. Overall, 32,000 people died.
Yet in the 2020-2021 season there were much fewer people sick or dying from the flu. Parents noticed their kids didn’t get their annual colds. What happened? Proponents of social interventions will point to mask mandates, school and business closures, social distancing requirements, hand washing, sanitizing, and vaccinations as the savior to significantly reduce flu spread with other respiratory viruses disappearing a happy side benefit.
Another interesting hypothesis points to "viral interference," the idea that a sufficiently strong respiratory pathogen could so occupy a susceptible population that it essentially supplants other weaker viruses.
Now that we are 18 months into the COVID-19 pandemic we have a lot more facts and science to work with about the virus and its impacts. Below are links to articles with more information related to COVID and potential implications of future outcomes.
Flu Has Disappeared for More Than a Year
The drop-off in flu numbers following COVID’s arrival was swift and global. Since then, cases have stayed remarkably low. The U.S. saw about 700 deaths from influenza during the 2020–2021 season. In comparison, the Centers for Disease Control and Prevention estimates there were approximately 22,000 U.S. deaths in the prior season and 34,000 deaths two seasons ago.
https://www.scientificamerican.com/article/flu-has-disappeared-worldwide-during-the-covid-pandemic1/
By Katie Peek, Scientific American, April 29, 2021
Covid-19 Meant a Year Without the Flu. That’s Not All Good News
The 2020–2021 flu season basically didn’t happen. Same for a couple other respiratory viruses. But that could make future seasons worse. And it’s not just the flu. Case numbers for some other respiratory viruses that have a seasonal rhythm have also bottomed out. Most likely, all the mask wearing, physical distancing, hand washing, and other "non-pharmaceutical interventions" that most everyone has been doing that has prevented the spread of Covid-19 also diminished those other viruses.
https://www.wired.com/story/covid-19-meant-a-year-without-the-flu-thats-not-all-good-news/
By Adam Rogers, wired.com, March 16, 2021
The Disappearance of Influenza
Recent evidence suggests that the Corona virus appears to resemble an invasive species that has disturbed the ecology of human-infecting respiratory viruses to the exclusion of most others. Has corona been so robust as to kill the regular flu? It has happened before. The flu of 1918 was so strong it appears to have cleared the playing field and its variants have become the dominant flu strains for decades afterwards up to the present.
https://eugyppius.substack.com/p/the-disappearance-of-influenza
By Eugyppius, substack.com, August 5, 2021
The future of the flu: Has Covid changed the virus forever?
In influenza, there is a thing called "antigenic drift," that during the course of an influenza season, the actual virus might drift from what was predicted by those who make the current season’s vaccine. That can make it more difficult to target the vaccine to the actual current version of the virus. Preparations are already underway for the 2021 flu season. The strains in circulation today – even though cases are few in number — get included in next season’s vaccine. The World Health Organization determines the formula, then manufacturers hit the assembly lines. Influenza vaccines have already shipped to the southern hemisphere, where the flu season is about to begin. Experts will be watching closely to see if cases there remain low during 2021.
https://wgntv.com/news/medical-watch/the-future-of-the-flu-has-covid-changed-the-virus-forever/
By Katharin Czink, Dina Bair, April 15, 2021
Why the 1918 Flu Pandemic Never Really Ended
An estimated 50 to 100 million people worldwide died from the 1918-1919 flu pandemic commonly known as the "Spanish Flu." It was the deadliest global pandemic since the Black Death, and rare among flu viruses for striking down the young and healthy, often within days of exhibiting the first symptoms. Infectious disease experts claim that this virus never really went away. After infecting a third of the global population, the H1N1 strain that caused the Spanish flu receded into the background and stuck around as the regular seasonal flu. But every so often, direct descendants of the 1918 flu combined with bird flu or swine flu to create powerful new pandemic strains, which is what happened in 1957, 1968 and 2009. Those later flu outbreaks, all created in part by the 1918 virus, claimed millions of additional lives. According to genetic analyses, the same novel strain of flu first introduced in 1918 appears to be the direct ancestor of every seasonal and pandemic flu we’ve had over the past century. Genetic traces of the 1918 virus can still be found in the seasonal flus that circulate today.
https://www.history.com/news/1918-flu-pandemic-never-ended
By Dave Roos, history.com, December 11, 2020
The Marek Effect - Imperfect Vaccination Can Enhance the Transmission of Highly Virulent Pathogens
Studies have shown that broad vaccinations can have the downside effect of creating greater pathogenicity of viruse. Recent science indicates that mass vaccination against SARS-2 and the rise of the Delta variant may be related. Could some vaccines drive the evolution of more virulent pathogens? Conventional wisdom is that natural selection will remove highly lethal pathogens if host death greatly reduces transmission. Vaccines that keep hosts alive but still allow transmission could thus allow very virulent strains to circulate in a population. This can happen with "leaky" vaccines that continue to allow the virus to transmit. When vaccines prevent transmission, as is the case for nearly all vaccines used in humans, this type of evolution towards increased virulence is blocked. But when vaccines leak, allowing at least some pathogen transmission, they could create the ecological conditions that would allow "hot" strains to emerge and persist. This theory proved highly controversial when it was first proposed over a decade ago, but scientists report experiments with Marek’s disease virus in poultry show that modern commercial leaky vaccines can have precisely this effect: they allow the onward transmission of strains otherwise too lethal to persist. Thus, the use of leaky vaccines can facilitate the evolution of pathogen strains that put unvaccinated hosts at greater risk of severe disease.
https://journals.plos.org/plosbiology/article?id=10.1371/journal.pbio.1002198
Plos.org, July 27, 2015 (Biology)
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