Tag: flu activity

Understanding Flu Season

Flu season starts.

A lot of folks get sick as flu season peaks.

Flu season eventually ends.

What’s to understand?

Understanding Flu Season

While we see flu activity at epidemic levels every year, some years are clearly much worse than others.

What kind of flu season will we have this year?
What kind of flu season will we have this year?

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.

More on Understanding Flu Season

Flu Season Predictions

No, I can’t see into the future…

I predict that I will continue to get a flu shot each year, at least until they come out with a universal flu vaccine.
I predict that I will continue to get a flu shot each year, at least until they come out with a universal flu vaccine.

But some things are very easy to predict.

Flu Season Predictions

Here are some predictions for this year’s flu season.

  1. 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.
  2. 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.
  3. Dozens of kids will die with the flu – most of them unvaccinated. Remember, 37 kids died in the mildest flu season we had.
  4. A little under half of adults will get a flu vaccine, even though the current recommendation is that everyone who is at least six months old without a true contraindication get vaccinated each year.
  5. A little over half of parents will get their kids a flu vaccine.
  6. 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.
  7. 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.
  8. Many people who aren’t high risk will be prescribed Tamiflu. Or Xofluza, because it is new.
  9. Tens of thousands of adults will die with the flu. Even in a mild flu season, the flu is very deadly.
  10. Some folks will continue to push the idea that there is a vaginal spermicide in flu shots, even though that anti-vaccine talking point has been refuted a thousand times already.

What else can you predict about flu season?

Some folks will think it is too late to get a flu shot.

It isn’t.

Get your flu shot if you haven’t and get protected for the rest of flu season.

Another bold prediction? Elderberry syrup and Oscillococcinum are not going to help prevent or treat your flu symptoms.

More Flu Season Predictions

Is It Too Late to Get a Flu Shot?

Have you gotten your kids their flu vaccine yet?

Have you gotten yours?

While I made sure to get my flu shot well before the start of flu season, it is not too late to get vaccinated and protected.
While I made sure to get my flu shot well before the start of flu season, it is not too late to get vaccinated and protected.

Believe it or not, it’s not too late.

Is It Too Late to Get a Flu Shot?

Why would anyone think it could be too late?

“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.”

CDC on Timing of Vaccination

Lots of folks focus on the “end of October” as being the best time to get a flu vaccine.

It’s Not Too Late to Get a Flu Vaccine

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.

Get your flu vaccine now.

More on Late Flu Vaccines

Who Dies from the Flu?

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.

As in most years, half of the kids who died of flu during the 2017-18 flu season had no underlying medical condition. Of those who did, the most common were neurologic and pulmonary conditions.
As in most years, half of the kids who died of flu during the 2017-18 flu season had no underlying medical condition. Of those who did, the most common were neurologic and pulmonary conditions.

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.

That’s a good clue that flu vaccines work and that everyone should get vaccinated and protected each year.

“Influenza vaccination during the 2015-2016 influenza season prevented an estimated 5.1 million illnesses, 2.5 million medical visits, 71,000 hospitalizations, and 3,000 P&I deaths.”

Estimated Influenza Illnesses, Medical Visits, Hospitalizations, and Deaths Averted by Vaccination in the United States

Flu vaccines aren’t perfect, but even when they are less effective than we would like, they have many benefits, including reducing your risk of dying from the flu.

Who dies from the flu?

Consider that one of the first flu deaths of the season was a 29-year-old Raleigh lawyer.

And the first pediatric flu death was an unvaccinated child in Florida without any underlying medical conditions.

Anyone can die from the flu.

Get your flu vaccine now.

More on Flu Deaths

Updated February 6, 2019

Is Flu Season Starting Already?

It seems like every year we get early reports of the start of flu season.

Why?

Because a few people had positive flu tests somewhere…

Is Flu Season Starting Already?

While there are many things about the flu that are unpredictable, including when flu season will start, peak, and end, there are some things that have become rather routine.

One of the things that we have come to expect every year is folks declaring an early start to flu season.

Not surprisingly, they are usually wrong.

A few positive flu tests doesn't mean that flu season is starting early.
A few positive flu tests doesn’t mean that flu season is starting early.

So why do some folks test positive in August or September if it isn’t because flu season is starting?

“During periods when influenza activity is low and there is low influenza virus circulation among persons in the community, the positive predictive value of influenza tests is low (that is, the chance that a positive result indicates that the patient has influenza is low – consider potential for a false positive result), and the negative predictive value is high (the chance that a negative result indicates that the patient does not have influenza is high – likely true negative result ).”

CDC on the Algorithm to assist in the interpretation of influenza testing results and clinical decision-making during periods when influenza viruses are NOT circulating in the community

When flu activity is low, such as it is during the summer or early fall before flu season has really started, you have a higher chance for a false positive flu test. So even though you have cold or flu symptoms and a positive rapid flu test, you might not really have the flu. The test is falsely positive. It’s wrong.

“Influenza prevalence varies between and within seasons. On the basis of our estimates, rapid tests are of limited use when prevalence is <10%”

Grijalva et al on Accuracy and Interpretation of Rapid Influenza Tests in Children

While other, more accurate flu tests are available, they are more expensive and take longer to process and get results. And since the diagnosis of the flu is often made clinically anyway, classic flu signs and symptoms during flu season, you typically don’t need a flu test unless being admitted to the hospital or if the results will really change how you are being treated.

So how do you know when flu season has started? You will see an uptick on flu activity maps. Hopefully you will have gotten your flu vaccine by then.

While flu season usually starts in October, it is the peak that we are usually more concerned about. That’s when you are most likely to be exposed to someone and get the flu.

When does flu season usually peak?

It depends, but usually sometime between December and March, typically in February. Getting back to how unpredictable flu season can be, there have been a few times that flu season has peaked as early as October though.

How can you reduce your chances of having a false positive flu test?

That’s easy. Don’t get a flu test unless flu activity is high in your area and you have classic signs and symptoms of the flu.

More on the Start of Flu Season