While we see flu activity at epidemic levels every year, some years are clearly much worse than others.
And while the severity of a flu season is easy to see after it is over, many of us could use a little help making sense of things when we are still in the middle of it.
Geographic Spread of Influenza Viruses – when you hear that there is widespread flu activity in a lot of states, this is what they are talking about. The only problem is that this doesn’t really tell you anything about the severity of a flu season. We get widespread flu activity in all states, or almost all states, each and every year as flu season peaks.
ILI Activity Indicator Map – like the maps showing the geographic spread of the flu, the ILI activity indicator map can help you tell where flu is spreading, but since it doesn’t necessarily represent the whole state, it can be misleading.
Influenza-like Illness Surveillance – the proportion of outpatient visits for influenza-like illness (ILI), or basically, how many people are going to the doctor with flu symptoms. Once we get above the national baseline of 2.2%, we know that flu season is starting in an area. How high can ILI get? Recently, it has peaked between 3.6% (2015-2016) and 7.5% (2017-2018). But that’s nationally. Because of wide variability in regional level data, you might see much higher ILI numbers in your state. For example, the regional baseline in Texas is 4%, while it is just 1.1% in Idaho. Still, widespread flu activity with a high ILI likely means a bad flu season.
Flu-Associated Hospitalizations – laboratory-confirmed influenza-associated hospitalizations. Overall, as flu season peaks, this can range from 4 to 5 per 100,000 population in a typical flu season, to 9 or 10 in a more severe flu season. This is also reported by age group. During a bad flu season, flu-associated hospitalizations will be high.
Mortality Surveillance – the proportion of deaths attributed to pneumonia and influenza. At some point in flu season, we get above an epidemic threshold and more people die with the flu, especially during a bad flu season.
Pediatric Deaths – pediatric influenza-associated deaths have been a nationally notifiable condition since the 2004 flu season and since then, on average, about 118 kids die with the flu each year. Last season was especially bad, with 185 pediatric flu deaths.
So how do you really know if it is a bad flu season?
Look for a high ILI%, high flu-associated hospitalizations, which will almost certainly be followed by a high mortality surveillance.
You also want to check viral surveillance data. Are the majority of influenza viruses being tested antigenically and genetically similar to the cell-grown reference viruses representing the 2018–2019 Northern Hemisphere influenza vaccine viruses? If not, that could mean a vaccine strain mismatch and a worse flu season.
And don’t be surprised by reports of widespread flu activity or rising ILI. That’s just flu season.
Here are some predictions for this year’s flu season.
We will have a flu season epidemic in the United States this year. Surprised by that prediction? Don’t be. Flu activity reaches epidemic levels each and every year. What we don’t always have are flu pandemics, during which flu activity is very high in multiple parts of the world. By definition, flu season is an epidemic.
Almost all states will eventually report having widespread influenza activity as flu season peaks. Again, this is not a bold prediction. It happens every year. How severe is flu season going to be? No one can really predict that, but we can look at the proportion of people seeing their health care provider for influenza-like illness (ILI) and laboratory-confirmed influenza-associated hospitalization rates as flu season moves along to get some idea. Remember, measures of the geographic spread of the flu don’t really tell you anything about the severity of flu activity.
A little over half of parents will get their kids a flu vaccine.
Some people who get a flu vaccine will still get the flu. You know the flu vaccine isn’t the most effective, but it still has plenty of other benefits, so even if you did still get the flu, hopefully you got a milder case, weren’t hospitalized, and didn’t die.
Some people who get a flu vaccine and get the flu will blame their flu shot, even though it is well known that the flu shot can’t give you the flu.
Many people who aren’t high risk will be prescribed Tamiflu. Or Xofluza, because it is new.
Tens of thousands of adults will die with the flu. Even in a mild flu season, the flu is very deadly.
“Balancing considerations regarding the unpredictability of timing of onset of the influenza season and concerns that vaccine-induced immunity might wane over the course of a season, it is recommended that vaccination should be offered by the end of October.”
While it is a good idea to get vaccinated and protected well before flu season starts, this is one of those better late than never kind of things.
Have you gotten a flu vaccine yet?
“CDC recommends that people get a flu vaccine by the end of October. Getting vaccinated later, however, can still be beneficial. As long as flu viruses are circulating, it is not too late to get vaccinated, even in January or later. While seasonal flu outbreaks can happen as early as October, most of the time flu activity peaks between December and February, although activity can last as late as May.”
CDC on Misconceptions about Seasonal Flu and Flu Vaccines
Then it’s not too late.
Get vaccinated and protected for the rest of the flu season.
But don’t wait much longer or you will risk getting the flu before your flu vaccine has a chance to start working.
While some folks still believe that the flu is a mild infection, most people understand that the flu is a very dangerous disease.
A dangerous disease that kills hundreds of children and tens of thousands of adults each year in the United States.
Who Dies from the Flu?
In addition to thinking that the flu isn’t dangerous, some folks misunderstand just who is at risk for dying from the flu.
While it is certainly true that some people at higher risk than others, including those who are very young, very old, and those with chronic medical problems, it is very important to understand that just about anyone can die when they get the flu.
Just consider the 2017-18 flu season, in which 185 children died.
In addition to the fact that half of the kids who died were otherwise healthy, without an underlying high risk medical condition, it is important to realize that up to 80% were unvaccinated.