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A Flu Season Primer: Coronavirus Pandemic Raises the Stakes

Analysis  |  By John Commins  
   September 09, 2020

How will the coronavirus affect the seasonal influenza, and vice-versa? What do we know about the combined effects of COVID-19 and the seasonal flu? These are big questions, and the answers are unknown.

With the Labor Day weekend in its wake, the United States now sails full steam ahead into the flu season. But with COVID-19 affecting broad swaths of the nation, healthcare providers are finding themselves in uncharted waters.

How will the coronavirus affect the seasonal influenza, and vice-versa? What do we know about the combined effects of COVID-19 and the seasonal flu? These are big questions, and right now the answers are unknown.

Brian Garibaldi, MD,  medical director at the Johns Hopkins Biocontainment Unit and an associate professor of medicine at Johns Hopkins University School of Medicine, provides HealthLeaders with a primer on the seasonal flu, and speculates on what the unprecedented upcoming season may bring. The following interview has been edited for brevity and clarity.

HL: When is the flu season?

Garibaldi: It varies from year to year, but usually cases start to spike in October and peak in December, January, then starts to taper off by March. But the flu season can shift from year to year. Sometimes it can last as late as May and you might start some cases in September.

HL: When do you encourage people to get flu shots?

Garibaldi: September/October is usually when we start to tell people to get vaccinated. There is a theoretical risk that if you get vaccinated too early immunity from the vaccine may be waning if the flu season goes on longer.

This year, we're much more worried about people just getting the shot. We want to make sure that as best we can, people are vaccinated against flu to reduce the possibility that people could get both flu and COVID, but also to reduce the burden on the health system from flu

HL: What's the mortality of the flu?

Garibaldi: Flu is usually in the range. 0.1%.

Depending on what studies you're looking at right now – it's always hard in the middle of an epidemic to understand overall mortality rates – COVID is at least 10 times higher, but at some series is much, much higher than that. We're still kind of learning

HL: Do the same underlying health issues that harm COVID patients harm flu patients as well?

Garibaldi: Yes. Those types of risk factors are similar; age, comorbidities, particularly things like diabetes, hypertension, heart disease, underlying respiratory issues, are all risk factors. But even the things that we're seeing with COVID, where younger people are getting sick, particularly if they're obese, those are factors that are probably at play in influenza as well.

HR: How many Americans die of the flu each year?

Garibaldi: I don't know the exact numbers off the top of my head, but the average number of deaths per year is probably on the order of 60,000 to 80,000.

HL: What sort of a flu strain are you anticipating this season?

Garibaldi: That's hard to stay. If you look at what's going on in in the southern hemisphere, South Africa for example, had a relatively mild flu season relative to normal for them, and that is probably related to their stricter COVID-19 precautions that were in place during the time that they would traditionally have their flu season.

If we're working really hard together to try to curb the spread of COVID-19, those same measures – social distancing, wearing masks, and avoiding large gatherings – the hope would be that maybe that would also tamper down the severity of our flu season.

HL: How do you respond when people say "COVID is just a virulent strain of flu."?

Garibaldi: It certainly has similar features of the flu. They both predominantly have respiratory symptoms, fever, malaise, and fatigue as their main symptoms. But by and large, the risk of having a severe outcome from COVID and the risk of mortality is substantially higher than it is with influenza. When you compare it to the flu, there's this danger of downplaying the significance of COVID.

HL: What do we know about the combined effects of COVID and influenza?

Garibaldi: There have been reported co-infections of flu and COVID, but not enough of them to really understand what that response will look like.

In the U.S., COVID peaked at the point when flu was on its way down, so we did not really get a sneak peek of what it looks like for someone to have both. The concern is that having both of those viral infections at the same time could potentially put you at risk for complications directly from the viruses and from the immune response to try to combat those two viruses.

HL: Are hospitals prepared for this double-whammy?

Garibaldi: The health system is very strained to provide care for all the patients who get hospitalized with flu. Close to 800,000 people a year get hospitalized for influenza. If you add the normal influenza burden on hospital capacity while COVID is surging, there are very few health systems that would be able to effectively deal with both at the same time.

COVID patients and flu patients are going to be competing for the same resources, the same providers, the same ER beds, the same hospital beds, the same personal protective equipment. That's probably the most important message to get out there is that there's a lot of uncertainty about what COVID plus flu looks like for an individual, but also for our community and health system.

HL: Could the tactics used to reduce COVID transmission reduce flu transmission too?

Garibaldi: That's my hope. It's still a little bit early to know for sure what the specific effectiveness of those interventions are, cut flu and COVID are spread through very similar mechanisms. It stands to reason that if you're successful at decreasing COVID transmission, you're at the same time probably going to reduce flu transmission.

HL: Is the flu as contagious as COVID?

Garibaldi: That's a complex question for two reasons. The first is that COVID itself probably has a higher attack rate than the flu. Let's say a given person with COVID probably infects more people than a given person with flu. Flu itself tends to last a little bit shorter but spread a little bit faster. The average time of incubation is only two to three days. But people can spread flu while asymptomatic, just as they can look COVID. So it's hard to compare the two.

COVID is probably a little bit more contagious in terms of the ability of one person to infect more people, but the flu potentially can spread more rapidly because of its faster cycle time.

HL: Do you think that public awareness of COVID might prompt more people to get vaccinated for the flu? Or, could it have the opposite effect, owing to public skepticism about the efficacy of a COVID vaccine? 

Garibaldi: That's an important question that I don't have the answer to. I hope that people's awareness of COVID as a severe respiratory infection and the publicity that the flu season and COVID have been getting makes people reconsider getting their flu shot if they haven't on a routine basis.

Obviously, there's a concern with how quickly things are being pushed forward with certain treatments for COVID, particularly with worries about vaccine safety.  There are some people who are going to be skeptical about any vaccine this year. But I hope the number of people who have been awakened to the risk of flu plus COVID and are willing to look at the data on safety for the flu vaccine and will get vaccinated this year.

HL: Is it possible that the COVID "second wave" could hit just as flu season is peeking?

Garibaldi: We're worried about a potential spike related to Labor Day. We saw spikes after Memorial Day. We saw spikes after the Fourth of July. So, if there's going to be a post-Labor Day spike, it's going to happen probably right as the flu season kicking off.

We're also not yet sure what role children play in the spread of COVID. There's very clear evidence that children are one of the primary drivers of influenza season. We're going to have to pay careful attention to what's happening in schools with COVID. If schools get shut down because of COVID, I suspect that that will mean that influenza transmission will decrease because children.

HL: What advice would you give to hospital leadership heading into flu season?

Garibaldi: As they've already been doing for COVID, making sure that they're paying attention to supply chain issues that are going to be related to personal protective equipment for respiratory viruses, testing equipment, to be able to make sure that they can continue testing both for COVID and for flu. And making sure that, as almost all hospitals do, they have easy access and requirements for the flu vaccine for their employees and their staff, to try to minimize the number of healthcare workers and providers who might miss time off work for being sick, but also to minimize the spread of respiratory viruses within the hospital environment.

We also need to recognize that there's a lot of uncertainty about what's going on and so being prepared for the worst while hoping for the best is a good strategy.

“We're worried about a potential spike related to Labor Day. We saw spikes after Memorial Day. We saw spikes after the Fourth of July. So, if there's going to be a post-Labor Day spike, it's going to happen probably right as the flu season kicking off.”

John Commins is a content specialist and online news editor for HealthLeaders, a Simplify Compliance brand.


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