(Bloomberg statement) – The Covid-19 pandemic fulfills many of the worst expectations public health experts in the US and Europe had of fall and winter. There is one thing they are worried about, but it doesn’t seem to be happening: a devastating “twilight” chemistry from Covid and seasonal influenza.
Instead, the flu is AWOL – at least so far. In New York City, where a practical number of emergency rooms for flu-like illnesses and other illnesses are posted daily, the number in the first half of December is less than a third of the latest norm.
This apparent absence of influenza is almost certainly not just a happy break. Neither is it the result of a cover-up where authorities count flu cases as Covid-19 cases (apparently a popular theory among some Covid denialist circles). It is It is conceivable that coronavirus cases are less likely to be considered flu-like illnesses in New York emergency rooms than in March last year, when Covid tests were rare and health care workers were less familiar with Covid symptoms. It is also possible that people will only avoid emergency rooms when they can. However, positive influenza test results recorded in FluView from the U.S. Centers for Disease Control and Prevention show an even more dramatic decline.
That dark blue line, barely distinguishable from zero for most of the year, is 2020. The positive test sum for the week ending December 5th – the latest available data – was only 56. In the same week last year, it was Case 6.435. The start of the flu season in the northern hemisphere is generally considered to be the 40th week of the year, ending October 3rd and making December 5th the end of week 49. Here are the positive tests for a decade for the first 10 weeks of the flu season:
Yes, the 2011-2012 flu season started with an even lower number of positive tests. However, this is misleading as the number of flu tests performed has risen sharply since then (although the number of Covid-19 tests performed this year is still a long way from coming). Those 511 positive results in the first 10 weeks of the 2011-2012 flu season came from 40,150 tests, giving a positive rate of 1.3%. This year’s 602 positives come from 401,112 tests, which corresponds to a positivity rate of 0.15%. So this flu season in the US is likely to be significantly milder than the least fatal flu season of the last decade and possibly the least fatal since the 1980s.
Similar trends can be seen around the world. “In the temperate zone of the northern hemisphere, influenza activity remained below cross-season levels,” summarized the World Health Organization in its latest weekly influenza update. This means that there is currently less flu in late autumn than in summer. The WHO and other health officials have understandably been reluctant to declare victory over the flu – it’s still early in the season and there is another disease that is wreaking havoc even when the flu isn’t present. The managing director of the smart thermometer manufacturer Kinsa Inc. is less reluctant and tells the New York Times: “It looks like the twin chemistry won’t happen.” And as of the 2020 flu season, which has already ended, it is clear that something extraordinary is going on.
Studies have shown that in the United States and Europe, incidence of flu decreased much more than usual in late winter and early spring of this year. And in Australia, where the flu season usually runs from April to September and efforts to fight Covid have been much more successful than in the US or Europe, there was no flu season at all.
Since the beginning of May (the last full autumn month in the southern hemisphere), five influenza tests in Australia have been positive, according to the FluNet database of the WHO. Nobody has had it since mid-July. Other countries in the temperate zones of the southern hemisphere have had similar experiences.
Why is this happening? The urge to get more people vaccinated against the flu this fall to stave off dreaded twilight chemistry may have had some impact, but that doesn’t explain why the incidence of the flu fell last spring. The obvious explanation is simply that the things that individuals and governments have done to slow the spread of Covid-19 have halted the spread of influenza, a respiratory disease that is transmitted in similar, if not identical, ways .
These measures were likely more effective against influenza than against Covid, since influenza is so much less contagious than Covid. A rough measure of the risk of infection is the basic reproduction number – the number of people any person can infect with the disease if everyone behaves normally. For seasonal influenza it’s around 1.3, for pandemic influenza it’s higher but still below 2. For Covid-19 it’s probably somewhere between 2 and 4.
Wearing masks, working from home, banning large gatherings, and other social distancing measures – along with more people gaining immunity from contracting Covid-19 – the effective reproductive number of Covid in the US doesn’t seem like much more than having lowered 1. (When was the last time I checked the estimates on rt.live. Tennessee had the highest rate at 1.22 and Wyoming the lowest at 0.85.) This apparently also brought the effective reproductive number for the flu well below 1.
One lesson to be learned from this is that the oft-heard complaint that the United States and many European countries have failed to fight the pandemic is false. Sure, a quick look at East Asia makes it clear that the West could have done much, much better. But given the success we’ve had in fighting the flu, it seems clear that we’ve also managed to slow down Covid. The disease recurrence that fall was bad, but it could have been much, much worse.
Another lesson is that “non-pharmaceutical interventions,” the artificial term for all of the things we’ve done to slow the spread of Covid while waiting for vaccines, should be a bigger part of the flu control toolkit . This does not mean that we should close all borders and restaurants every winter, but that we should take more cost-effective measures such as hand washing seriously, wear a mask when you are uncomfortable, work from home when you have been exposed and keep sick visitors and Workers outside of nursing homes could save thousands of lives each year. And if a new pandemic flu emerges that is just as deadly as, say, the 1918 strain (which was much more deadly than Covid-19, especially to young people), more costly interventions would almost certainly be worth the price.
The waiting time for a vaccine against a pandemic flu would be shorter than for Covid-19. It took about six months from the identification of a new strain of H1N1 influenza in 2009 to a widely used vaccine. In a presentation last week at a conference of the European Scientific Working Group on Influenza, vaccination professor Florian Krammer of the Icahn School of Medicine at Mount Sinai in New York said that with the right preparation, the waiting time could be reduced to three months. If mask mandates, social distancing, and other non-pharmaceutical interventions can stop influenza and only need to stop them for three months, it would be insane not to use them.
This column does not necessarily reflect the opinions of the editors or Bloomberg LP or its owners.
Justin Fox is a Bloomberg Opinion columnist on business. He was the editor-in-chief of Harvard Business Review and wrote for Time, Fortune, and American Banker. He is the author of “The Myth of the Rational Market”.