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Twindemic – Hype or Hazard

Is anyone surprised that some folks are already talking about a coming twindemic, or the possibility of getting hit with both a COVID-19 and influenza pandemic at the same time?

What is a Twindemic?

First things first though.

It is very important to remember that flu epidemics are routine. They happen every single year. On the other hand, flu pandemics are very rare. In fact, there have only been five influenza pandemics, including the well known 1918 Spanish flu pandemic and the 2009 swine flu pandemic.

So the twindemic, if it happens, almost certainly won’t be twin-pandemics.

What else could a twindemic look like?

“Pandemic refers to an epidemic that has spread over several countries or continents, usually affecting a large number of people.”

Lesson 1: Introduction to Epidemiology

How about a continued COVID-19 pandemic with a flu epidemic?

As you can imagine, even that would cause a lot of problems, as both cause life-threatening disease, and they share many of the same symptoms.

In addition to the confusion of not knowing if someone has flu or COVID-19, what happens if someone gets both, or gets one while recovering from the other? Or if a health system already overburdened with COVID-19 patients has to suddenly start caring for a lot of sick people with the flu?

What Happened to Last Year’s Flu Season?

But don’t we already know what will happen? After all, we first started to see SARS-CoV-2 infections during last year’s flu season.

A flu season that started early, and ended as one of the deadliest, with 188 pediatric flu deaths.

Flu tests were mostly negative when ILI activity was once again peaking in late March because those influenza like illnesses were caused by SARS-CoV-2.
Flu tests were mostly negative when ILI activity was once again peaking in late March because those influenza like illnesses were caused by SARS-CoV-2.

A flu season that was ending as COVID-19 cases started to peak.

Which brings up an interesting question… Did all of the social distancing and mask wearing that we did to combat the SARS-CoV-2 virus also help put an end to last year’s flu season?

“Intuitively, it makes sense that wearing masks, social distancing, working from home, closing schools, and other strategies to minimize the spread of COVID-19 would lessen transmission of other respiratory infectious diseases as well.”

What Happens When COVID-19 Collides With Flu Season?

While it may have been ending anyway, there is evidence from other countries that mitigation strategies for COVID-19 can reduce the risk of a bad flu season.

Australia hasn't had much of a flu season this year.
Australia hasn’t had much of a flu season this year.

Mitigation strategies like social distancing, mask wearing, and closing schools, etc.

Twindemic – Hype or Hazard

So what about this year’s flu season?

Can we count on everyone wearing masks and social distancing to help us avoid a flu season this year?

Of course not!

For one thing, many of those countries in the Southern Hemisphere that are seeing lower rates of flu because of social distancing, mask wearing, and other COVID-19 mitigation strategies have also been seeing lower rates of COVID-19!

If you are in an area with continued high rates of COVID-19, then you likely shouldn’t count on folks wearing masks or practicing social distancing to keep the flu away.

What can you count on instead?

While the flu vaccine has been as low as 10% effective in a few years, it is typically about 40 to 60% effective!
While the flu vaccine has been as low as 10% effective in a few years, it is typically about 40 to 60% effective!

Getting a flu vaccine!

“Our results suggest a reduction in COVID-19 mortality associated with higher influenza vaccination rates in the elderly population. Specifically, we found that overall, a 10% increase in vaccination coverage was associated on average with a statistically significant 28% decrease in the COVID-19 death rate.”

Zanettini et al on Influenza Vaccination and COVID19 Mortality in the USA

That’s especially important this year, as in addition to the usual benefits of a flu vaccine, several studies have shown a positive effect in relation to COVID-19.

“Influenza vaccination programs might need to adapt and extend the duration of vaccination campaigns to accommodate stay-at-home orders and social distancing strategies aimed at slowing the spread of SARS-CoV-2. These circumstances might necessitate consideration of starting vaccination campaigns earlier (i.e., as soon as vaccine is available, which can be as early as July or August) to allow sufficient time to vaccinate the population and avoid some persons going unvaccinated for influenza. When possible, such considerations should be balanced against the potential waning of protection from influenza vaccination, particularly for persons aged ≥65 years.”

Prevention and Control of Seasonal Influenza with Vaccines: Recommendations of the Advisory Committee on Immunization Practices — United States, 2020–21 Influenza Season

Let’s do everything we can to keep the case counts of both COVID-19 and flu down by social distancing, wearing masks, and getting our flu vaccine.

More on This Year’s Flu Season

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