Is This Season’s Flu More Severe Than Usual or Just Highly Active?

At this point in the flu season people often wonder if all the media hype is part of an orchestrated effort to panic people about flu, or if it is really signaling serious concern.

While we’re seeing stories about emergency rooms in California turning away ambulances because of overcrowded with flu patients, or Alabama declaring a state of emergency due to the high number of flu cases, we’re left to wonder….is this year’s flu season more severe than usual or just highly active at the moment?

A recent CDC media briefing has helped clarify the following concerns regarding the latest flu activity in the U.S.: 

Right now, flu is widespread everywhere.  

One of the most notable differences between this season and others is in relation to the geographic spread of flu. This is the first time over the course of 13 years of surveillance data that the entire nation is experiencing widespread flu at the exact same time, as can be noted by the color of CDC’s flu surveillance map below.



Activity is severe right now.

One of the ways the CDC tracks influenza activity is to record the number of lab confirmed cases of flu and hospitalizations by week. What they’ve noted is a very rapid increase in the number of people seeing their healthcare providers for flu diagnosis, along with a rapid rise in the numbers of people being hospitalized with lab confirmed flu. For instance, this week’s surveillance data indicates that there’s been 22.7 hospitalizations per 100,000 people in the U.S., which is up considerably from the 13.7 number recorded last week.

So far this season, influenza A (H3N2), has been the most prevalent strain in circulation. Unfortunately, historically it is often the strain linked to more severe illness, especially among children and older individuals above the age of 65. Interestingly enough, the current flu surveillance observations seem to be in line with two more previous H3N2 dominant seasons; the 2014-2015 and 2012-2013 seasons.

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Additinally the hospitalizations so far this season seem to be in line with other H3N2 predominant seasons, with the highest rates among those over the age of 65, those between 50-64, and children under 5 years of age.

Flu can cause mild disease in some, but severe disease and death in others.


Sadly, this week there have been an additional 7 pediatric flu deaths, totalling 20 pediatric deaths so far this season.  While children are at great risk, there are plenty of reports of otherwise healthy adults who have been hospitalized or died from flu this season.

Peak season may have started early, but there are many more weeks to go.

Speaking to the media on behalf of the CDC on Friday, Dr.  Jernigan explained,

“If we look at the timing of the season, even if we have hit the top of the curve or the peak of the seasonal activity, it still means we have a lot more flu to go.”

He went on to suggest that there will likely be at least 11 to 13 more weeks of elevated influenza activity this season, before activity begins to subside. Even though it can take about two weeks for protection from vaccination to set in, Dr. Jernigan explained that we still have a lot of flu season to get through and that vaccination efforts should continue as long as influenza viruses are circulating.

While we are seeing a lot of H3N2 circulating now, we are also seeing H1N1 show up in states that have already had H3N2 activity. And we know that B viruses also tend to show up later in the season. Each of these strains are covered in the vaccine, so flu vaccination now can still help to prevent, or lessen the severity of flu throughout the remainder of the season.

Vaccination is our best defense.  

While flu vaccination is far from perfect, it remains our best defense. Not only can it help prevent flu, but it can also help lessen the severity of symptoms if a vaccinated person does end up getting infected.  This can reduce the chances of an individual being hospitalized or dying from flu.


In fact, a recent study showed that influenza vaccination reduced the risk of flu-associated death by 65% among healthy children and by 51% among children with underlying high-risk medical conditions. Another study indicated that many older adults benefit from repeated flu vaccination. When getting vaccinated in both the current and previous seasons, the study found flu vaccination was 74% effective in preventing ICU admissions in older individuals and 70% effective in preventing deaths among older adults.


Manufacturers are reporting that they’ve shipped more than 151 million doses of flu vaccine this season, so there shouldn’t be a problem finding a flu vaccine in your area.  Simply refer to the flu vaccine finder for assistance.

We won’t know preliminary flu vaccine effectiveness until February.  

As Dr. LJ Tan explained in a previous post, there has been some confusion over this season’s flu vaccine effectiveness.  In some cases, the media has been using Australian data for the H3N2 strain in Australia as an indication of what we can expect here in the U.S.  However, historical data from the U.S. is more indicative of what we might expect from year to year.

Last season, vaccine effectiveness in the U.S. was 39% and effectiveness against the H3N2 strain was 32%.  However, if you look back beyond just last season, multi-year pooled vaccine effectiveness against the H3N2 strain has consistently been between 30 – 40%, while effectiveness against influenza B viruses has been about 54%, and against H1N1 viruses as high as 61%.  That’s good news because even though this season appears to be dominated by the H3N2 strain of flu, the surveillance data is already indicating that there are H1N1 strains and B strains circulating as well, and the vaccine is known to protect against those strains as well.

However, it’s still too early to predict this year’s efffectiveness, and we’ll just have to wait until mid-February, when the early preliminary data for the current season’s flu vaccine effectiveness will be reported, to know more.

Know flu symptoms and see your doctor.

It’s important to know the symptoms of flu so that you can seek medical treatment when needed.  Antiviral drugs are available and approved for treatment of the flu and if taken early can lessen symptoms, shorten duration of illness, and help prevent complications.

However, not everyone may need to get antivirals. The people who should get antivirals are those who are at higher risk of complications and severe illness from flu including those 65 years old and older; young children; pregnant women and those with chronic health conditions such as heart disease and diabetes.

The CDC is in regular contact with manufacturers of antivirals and there is currently no shortage of antivirals in the U.S.  However, there might be some difficulty locating antivirals in areas with high flu activity.

The most important thing to reduce transmission of flu is to stay away from people who are sick, stay home from work or school if you get sick, cover your coughs and sneezes, and wash your hands often.


If you have questions about flu or flu vaccination, let us know in the comments below or refer to these additional resources:

For other reading on this topic, visit Vaxopedia’s post Flu Season Hype or Hazard.


  1. January 13, 2018 at 4:55 pm

    Makes you think of/remember all the years flu might have been quiescent.


  2. carl dick
    January 13, 2018 at 5:24 pm

    was h3n2 strain included in the flu vaccine this season?


  3. Christine Vara
    January 13, 2018 at 6:15 pm

    @carl dick Yes, this year’s flu vaccines protect against the three or four viruses (depending on vaccine) that research suggests will be most common. For 2017-2018, three-component vaccines are recommended to contain:

    an A/Michigan/45/2015 (H1N1)pdm09-like virus (updated)
    an A/Hong Kong/4801/2014 (H3N2)-like virus
    a B/Brisbane/60/2008-like (B/Victoria lineage) virus

    Quadrivalent (four-component) vaccines, which protect against a second lineage of B viruses, are recommended to be produced using the same viruses recommended for the trivalent vaccines, as well as a B/Phuket/3073/2013-like (B/Yamagata lineage) virus.

    This information is taken directly from the CDC website at


  4. carl dick
    January 13, 2018 at 6:20 pm

    why does the flu always start in SE asia and why does it always start in the Louisiana area of the US


  5. Joel A. Harrison, PhD, MPH
    January 14, 2018 at 10:53 am

    Historically flu has not always started in “SE asia”, actually China; but nowadays the Chinese have a HUGE business of raising enormous numbers of pigs, ducks, and chickens, literally 100s of millions. The probability for genetic mutations increases; but worst, seabirds are a reservoir for 17 types of the HA gene and 11 types of the NA gene, the two that flu vaccines target. If a seabird poops anywhere where pigs, ducks, and chickens are being raised, the risk that one of their genes will be incorporated in a new flu is present. In addition, pigs have receptors for both avian flus and human flus, so they can get both and mix the genes up. But flus from many years ago also started elsewhere. Some believe the 1918 flu pandemic started in the US actually Kansas.


  6. Mary Koslap-Petraco DNP CPNP
    January 16, 2018 at 10:14 pm

    We vaccinate not just for ourselves but for out patients. Influenza is a serious disease. It hospitalizes and kills the most vulnerable among us…the very young and the very old. And so far it looks like the vaccine is more effective in the US than it was in Australia.


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