How COVID-19 is changing the cold and flu season
By mid-December, the Northern Hemisphere is usually well into the start of its annual cold and flu season — but so far this year, even as the COVID-19 pandemic surges in dozens of countries, the levels of many common seasonal infections remain extremely low.
The pandemic caused by the SARS-CoV-2 coronavirus has infected at least 67 million people and killed 1.5 million worldwide. The patchwork of responses intended to fight the pandemic — from temporary lockdowns to mask wearing, social distancing, enhanced personal hygiene and reduced travel — has had a huge impact on other common respiratory illnesses, too.
In the Southern Hemisphere — now past its winter — seasonal influenza hardly struck at all. That looks as though it might happen in the north, too. Conversely, some common-cold viruses have thrived, and tantalizing evidence suggests that they might, in some cases, protect against COVID-19.
Despite humanity’s long history with colds and flu, the viruses that cause them still hold many mysteries. Scientists hope this year’s disrupted seasons could reveal new information about the transmission and behaviour of these unwelcome annual guests: how these viruses respond to health measures, how they interact and what that might mean for long-term disease burdens. “This is a natural experiment for so many respiratory viruses,” says Sonja Olsen, an epidemiologist at the National Center for Immunization and Respiratory Diseases, part of the US Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia.
The influenza fizzle
In May, at the tail end of the first wave of COVID-19 deaths in many nations, and when some of the strictest lockdowns were in place, health workers noted an abrupt and early halt to the 2019–20 flu season in the Northern Hemisphere.
That might partly have been an artefact caused by fewer people coming to a clinic for testing, experts say, but it was also attributable to the effectiveness of policies such as social distancing. After the pandemic started, positive tests for the flu virus plummeted by 98% in the United States, for example, whereas the number of samples submitted for testing dropped by only 61%1. In the end, the US 2019–20 flu season was rated as ‘moderate’ by the CDC, which estimates that 38 million people fell ill with influenza, and 22,000 people died. That’s fewer than in recent years, but not unprecedented.
After the flu season in the north ended early, it hardly got going at all in the Southern Hemisphere. There were astonishingly few cases of seasonal flu there from April to July 2020 — even as global COVID-19 cases continued to climb. In Australia, Chile and South Africa, a grand total of just 51 cases of flu were spotted in more than 83,000 tests1. “We know it’s less transmissible than coronavirus, so it makes sense,” says Olsen, but the decline was still “greater than expected”. Influenza’s absence has been attributed to pandemic-response measures, but they don’t tell the whole story.
“Some South American countries haven’t done such a good job controlling COVID, but even there flu is low,” says virologist Richard Webby at St Jude’s hospital in Memphis, Tennessee. “I don’t think we can put it all down to mask wearing and social distancing.” He suspects that the dearth of international travel played a part. Flu typically travels around the world from one winter to another, while maintaining a lower year-round presence in the tropics. Although the mechanisms underlying this behaviour aren’t entirely clear, the movement of people clearly contributes.
Increased influenza vaccination might have contributed to the disappearance, too. Australia, for example, saw more than 7.3 million flu jabs administered by 20 May 2020, compared with 4.5 million by that date in 2019, and 3.5 million in 2018. It’s unclear if that trend will hold in the north.
Vaccination rates in the United States for seasonal flu have been trending upwards for years: slightly more than half of the US population over six months of age was vaccinated in 2019–20, up 2.6 percentage points from the previous year. But it is unclear whether Americans will be more or less inclined towards flu vaccinations this year, particularly given the tumultuous backdrop of the pandemic and the change in president.
Viral unknowns
Most experts are cautiously betting on a very mild flu season for the Northern Hemisphere this year. That would be good news on many fronts — in particular, it would help to alleviate the potential burden on the health system, from hospitals to testing centres, caused by simultaneous waves of flu and COVID-19. But surprises could be in store.
No one really knows, for example, why one nation, such as Australia, can be hit hard by influenza for several years while a neighbouring country, such as New Zealand, sees very low rates, says Webby. Even influenza’s seasonality isn’t entirely understood, nor exactly how it travels around the globe. “We don’t have a real good handle on why it’s a winter disease,” he says. Untangling lessons about flu from this year’s data will be interesting but difficult, Olsen says, because pandemic policies and compliance vary on the national, state and even neighbourhood level.
Read more at www.nature.com
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Chris
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Can the author prove that sars2 exists? Nope. Has the cold and flu season changed, no. They simply recategorized the people as having a non existent covid19 case. Remember if you come up positive on a failed pcr test then you are labeled as covid19 instead of what you actually have. This has only made lazy doctors. People who are in hospitals with covid19 are not being tested to find out what they actually have so there is an increased chance of their death.
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Ron
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Why does covid19 continue to be almost universally accepted when a causative virus has not been isolated?
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Jerry Krause
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Hi Chris (and Carl A. B.),
Has someone developed a test for the common cold which we all have had and survived because we did not have preexisting more serious health problems. The longer one lives the more likely we might acquire these more serious health problems.
I believe Churchill stated something like this: “The only fear we have to fear is fear itself.” So don’t let fear control you life.
Have a good day, Jerry
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Lloyd
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I remember it as FDR.
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Kathleen
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That is precisely right. They have categorized the influenza flu deaths over to China virus and if you look at charts the levels are in direct proportion to each other (increase vs decrease). This is all just a joke. China v. is less deadly than influenza and they know it. It seems to be affecting certain people quickly and badly but then others almost nothing at all. And as stated below, the causative virus has not been isolated and therefore the PCR tests are useless and are just throwing out hits and misses at random. It’s all such a joke. I can’t believe some people still believe all of this fake news and are afraid. The deep state dems and bad actors interferring with humanity to regain power. That’s all this is about.
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Doug Harrison
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This is a good article as it exposes the vast gulf between the official narrative and what is really happening. Now Richard Webby can get his information where he likes but I have personal experience. I was suddenly struck down with a severe influenza/ pneumonia in September 2019. I was very ill but was discharged from hospital after two nights because I had improved a lot and the hospital needed beds for a rush of flue/pneumonia patients which is a rather different story from Mr Webby’s about New Zealand.
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Jerry Krause
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Hi PSI Readers,
“The patchwork of responses intended to fight the pandemic — from temporary lockdowns to mask wearing, social distancing, enhanced personal hygiene and reduced travel — has had a huge impact on other common respiratory illnesses, too.”
But is suspect the greatest impact was due to the shutting down of ‘live’ elementary schools where there were commonly 25-35 students per classroom. For I know that in these lower grades, say before the 5th or 6th grade, I ‘caught’ about every childhood disease known. And, to my knowledge, I and my fellow students survived every case of a cold or of the common flu. I suspect that sometimes my and other parents caught colds and maybe the flu from me.
I know I had been vaccinated for smallpox and I am not sure about diphtheria. For when I was in the third grade my brother, who was 10 years older than I and out of high school, got diphtheria and our family was immediately given a booster shot and quarantined. My bother survived and recently died, of cancer and not of the flu, a few months short of 90 years. And he was very satisfied with the productive life he had lived so I, at least did not mourn.
But back to his case of diphtheria. We lived on a farm in an county of maybe 7000 citizens and many of these 7000 were cared for by our one doctor. And to this day, we do not know how my brother ‘caught’ diphtheria.
Just some information to ponder.
Have a good day, Jerry
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