CDC’s latest weekly report announced the current flu season has surpassed the swine flu pandemic of 2009.
Holy crap, that sounds really bad, but what does the CDC mean by that?
Are more people dead? Are there more people sick? Are we all going to die?
The metric they are announcing is the percentage of patients presenting flu-like symptoms to health care providers. A metric so specific it kind of sounds meaningless.
Flu-like symptoms include: cough, fever, muscle aches and chills, headaches, and fatigue. Symptoms that can be caused by any number of other diseases.
So, my questions become less apocalyptic and more like, “Is the CDC inflating their numbers? And can we trust their data to actually represent reality?”
We dug into the data and found the wonderful world of statistics to find those answers!
By-the-way this is going to be filled with graphs, charts, and numbers. All provided by the CDC, Lee Memorial Health System and the Florida Department of Health. I hope you brought a pencil. And if you don’t have the time to learn how the CDC makes its numbers skip to this time code on the screen for the “too long, didn’t watch” portion.
I got my pencil in hand so here we go!
“Is the CDC inflating their numbers?”
The number the CDC is freaking out about, as mentioned earlier, is the percentage of patients presenting flu-like symptoms to health care providers. which last reported as 7.6%.
The CDC gets these number from a network of health providers that record the number of visits in each state and posted on this website called FluView.com. For reasons, not known to us at the time of this recording, Florida’s information isn’t included this season on the graph. They take the number visits for Flu-like symptoms and divide that by the total number.
Voila, you get the percentage of illnesses of those who have the flu for that state.
The CDC then takes the percentages of all the recorded visits from all the states and create the national percentage.
BOOM! We’re at 7.6% of the total visits to healthcare providers in the country.
Extrapolation is as common in statistics as numbers.
Has your brain exploded yet?
It’s just statistics which leads us to our second question: “Does this actually reflect reality?”
The one thing you’ll never hear from people who do these numbers are things like: “100% sure” and “Absolutely, these are the exact numbers!” It’s always, “most likely, high probability, or high level of confidence.” That’s because we don’t have enough resources to actually count all 325,719,178 Americans, or labs test them every week to see how many people have the flu. Since every flu season lasts about eight months, that would mean 104,230,133,696 tests would have to be performed in total.
They pull a sample instead. Think of samples like the resolution of your TV screen. The smaller the sample the fuzzier the picture. But if you get more data and increase your sample, the clearer the picture on your screen will be.
That is why the CDC will say “with confidence” they are a certain percentage of correct on these rates. The goal for most statisticians who do this kind of work is 95% confidence they are correct.
That’s where your faith in math comes in. The way the sample size that is extrapolated is a mathematical methodology to account for all the things we don’t really know and can be too difficult to find out absolutely. So we’re stuck with 95% likelihood of being correct.
Hey, that’s an A.
And welcome back viewers with time restricted schedules!
We are going to answer if the CDC can really say the current flu season is really going to surpass the 2009 swine flu?
We dug into the reported numbers the CDC had of cases of flu-like symptoms this year from their ILINetwork and compared it to the data they had available from 2009. The sample size for those of you stuck with me all the way through and we created this cumulative graph using the data from the CDC.
The blue line is 2009 and its longer because that flu season was completed. The orange line is current flu season.
And yup, the number of cases has the number of cases back in 2009 when swine flu was at its peak. Now we won’t actually know how “bad” it is until the flu season is over.
Right now, it’s very concerning and will become alarming if any of these three things happen.
- Back in 2009, this was the peak of the season. We currently haven’t reached our peak yet. If the cumulative rate of increase keeps going up this sharply the number of people getting the flu will also increase sharply.
- If the rate plateaus and doesn’t come down in a long time. The line will go up but not as sharply. If this happens, this year’s flu season will have more cases overall.
- If both 1, 2 happens then 1 happens again and doesn’t stop. That’s when people in Hazmat suits start running around.
- We won’t know for another couple of weeks.
Now, let me through some grains of salt on all of this!
The Florida Department of Health has its own sample size. Back in 2009, 8% of hospitalizations were from the Flu during the season’s peak, however, not all hospitals were able to report their numbers to the Florida Department of Health. That didn’t happen until 2014. This year our state is at 12% of all hospitalizations are from the flu. Since our sample is larger than what it was 9 years ago, this percentage is more accurate than the one in 2009.
To be a little more local, Lee Health Memorial system has seen a decrease in their rate of cases coming in. Flu season doesn’t end until around May and there have been seasons when the flu peaked twice.
And it may peak twice because scientists don’t really know why this Flu strain is more intense than previous seasons.
Once again, we will wait and see.
I think my brain hurts now.