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

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.