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Chico State virologist on why the U.S. might see a “rough” flu season

File photo of influenza vaccination
U.S. Air Force photo by Tech. Sgt. Jocelyn A. Ford
File photo: Influenza vaccination

Influenza cases usually begin to increase in October in the United States, according to the U.S. Centers for Disease Control and Prevention. While every flu season is different, one indicator of what this season might be like is to look at flu activity in countries in the southern hemisphere, which start earlier than those in the northern hemisphere. To get some projections, NSPR’s Sarah Bohannon recently spoke with Chico State Associate Professor of Biological Sciences, Troy Cline, about what North State residents need to know and how Australia's flu season might tell us about our own.

This interview has been edited for brevity and clarity.

Interview Highlights 

On high flu case rates in Australia this year 

Australian epidemiologists and public health officials are reporting influenza activity and a case rate that is above the five-year average. This isn't terribly surprising, [it] is somewhat to be expected because remember, our last several flu seasons have been quite abnormal. In 2020-2021, we really didn't have a flu season at all because of COVID mitigation measures that were in place. In 2021-2022, the flu season here started out relatively normal, but seemed to end earlier than it normally does and that may have to do with COVID mitigation measures as well.

On predictions about the kind of flu season the U.S. might experience 

It's expected that our flu season is probably going to involve a higher case rate than normal. Part of that is because we're getting back to not masking, businesses aren't shut down, schools are fully open. So we're expecting to have a higher-than-average flu season. Part of that is because for the last two seasons our flu numbers have been really low in the United States, so overall immunity in the population is lower, which means more of us are susceptible and primed to be infected again, maybe for the first time in a few years.

On precautionary flu measures for the general public and those at high risk 

The flu vaccine is always good for everybody. So the Centers for Disease Control and Prevention (CDC) recommends the influenza vaccine for everybody. Children all the way up to those who are over the age of 65. And the flu vaccine is very protective. It is a very effective vaccine at protecting against hospitalization, ICU admission and fatality. There have been a number of studies over the last five to 10 years showing that the influenza vaccine is effective at preventing severe disease, and hospitalization and death. The range in those studies is anywhere from 40% up to 70% effective at preventing severe illness.

Something else that people should have in mind, especially for those who are at high risk — that's going to be those who are over the age of 65, or those who have some underlying complication, some other pulmonary or heart disease. So something to consider for these individuals is we're going to see influenza virus and SARS-CoV-2 co-circulating this year. But symptoms are going to be really similar. You're coughing, you're fatigued, you have chills, night sweats, headaches, these kinds of symptoms, could be either COVID-19 or influenza virus. There are studies that show people who are co-infected with those two viruses usually do worse than those who are dealing with a single COVID illness or influenza virus infection. So for those who are at particularly high risk for severe illness, one measure that's going to be really important for those people this year, is to get tested. If you have respiratory symptoms get tested because there are therapeutic measures that can be taken to treat the illness, but those are going to be different for COVID-19 than they are for influenza. And so those people are going to want to as soon as they start having those respiratory symptoms get tested to find out whether it's COVID, or whether it's influenza virus, and then talk with their physician about whether or not one of these therapeutic treatment measures is right for them.

On the best time to get a flu vaccine

I think the best time is whenever it fits your schedule. So, if that's now, go get your flu shot now. If you're really busy right now, and it's going to be two or three weeks from now, don't not get it because it's November or December. Still get that vaccine. It's still going to protect you through a flu season that can last well into the spring. So this is the time of year here in mid-October when the CDC starts reporting weekly influenza activity across the country. Overall, influenza activity is low across the country, but in the southeast and even in Texas, influenza activity is already considered high. Which is a little bit abnormal for this time of year. And so that's where some of the predictions are coming from, that this could be a particularly bad flu year. So we're already seeing flu activity begin to tick up in parts of the country. So this, even if you don't typically get your flu shot this time of year, maybe this year you want to get it a little bit earlier than the normal.

On the likelihood of a flu and COVID-19 “twindemic” 

We don't know yet. I think there's still a lot to learn about how these two viruses are going to play off one another, and what sort of relationship they're going to settle into. It's possible our typical flu season might shift. What we think of as normal flu seasonality could change, now that another prevalent respiratory virus is on the table. So, I'm not sure. I'm not hearing the word twindemic as much anymore this year, but I think we are going to see these viruses co-circulating this year. I think we're due for [a] COVID-19 surge. There's a new booster shot out there that people should get. If it's been at least two months since a previous COVID booster, then you should get that booster to protect you for the upcoming potential surge in COVID cases. You can get a COVID booster and the flu shot at the same time. The CDC recommends and allows for that. So when you go in to get your flu shot, maybe getting that COVID booster would be a good thing to do as well.

On much of the public not seeing the flu as a serious illness 

I see where those people are coming from, and I sort of have to fight against that pattern of thought myself. Because I'm a middle-aged, relatively healthy man. And so I recognize that if I were to get an influenza virus infection, and I have had influenza virus infections in the past, and you feel really crappy for a week or a week or a week and a half, but you get over it, the illness resolves, and you get over it without any serious complications. But I think people also have to consider that even if they're not at risk themselves for severe disease. Most of us do in some capacity associate with people who are at high risk. So we have elderly parents or grandparents. We have really young children, or cousins, or nieces, or nephews or grandchildren, who are also at high risk because their immune systems are not yet fully developed. And so when I'm getting a flu shot, I'm cognizant of the fact that I'm also taking a step to protect the overall wellness of the community, and those with whom I associate. And there are also people that we associate with, interact with, who are relatively young or middle-aged, they look healthy and vibrant but we don't know if they deal with some sort of immunosuppressive state or illness that would leave them at high risk. And so we can't always tell who is at high risk, and who we are potentially exposing to a serious illness, if we aren't protecting ourselves.

On the number of people who die from flu each year in the U.S.

The number of influenza related deaths ranges anywhere from 10,000 to 15,000, up to 35,000 to 50,000 annually in the United States. And the overwhelming majority of those deaths are in people over the age of 65, or with underlying health conditions. So again, those people should definitely get their flu shot, and take those measures to protect themselves from severe illness. Last year, I think the number of influenza deaths in the United States was estimated to be somewhere between 5,000 and 15,000, so it was low as flu seasons go. But again, overall case rates and infection incidence was low because the season sort of slowed down and seemed to end really early because of COVID-19 mitigation measures that were in place. We're not going to have those COVID-19 mitigation measures in place like we have the last couple of years. So I would expect to see the number of influenza-related deaths jump up.

On Cline’s additional thoughts this flu season 

I was looking just this morning [Thursday, Oct. 20] at the previous five influenza virus seasons in the United States, and in case rates for those five years kind of overlaid against one another compared to how this season is just beginning to shake out. And so again, the CDC is just now beginning to report influenza activity and case rates, but we're already seeing case rates that are higher than they have been for each of the past five years. That doesn't mean we're in for a catastrophic, terrible flu season, but it is an early indicator and an early warning that we could see a rough flu season. And so the more we can do to protect ourselves and prevent illness now will help to mitigate the effect of this flu season.

Sarah is an award-winning host, reporter, producer and editor. She’s worked at North State Public Radio since 2015 and is currently the station’s Assistant Program Director. She’s responsible for the “sound of the station" and works to create the richest public radio experience possible for NSPR listeners.