Flu Season in Review: 2018-2019

As the days get longer and our kids begin counting down to summer break, we can finally say that this unusually long and frustrating flu season has come to a close. While Kinsa’s illness signal still shows roughly 2.2% of the country exhibiting symptoms (more than 60% above this time last year and even higher compared to our 10 year average), we predict that we’ll be at off season levels by the end of the month. So it’s time to look back and show just what made this flu season such a strange beast.

A few highlights:

  • The 2018-2019 flu season started earlier than the past two years, with unusually high illness incidence in October and November.
  • While this season exhibited a similar rise and peak to last year (high point: February 12th with U.S. cold & flu levels at 6.5%), we saw an atypical third peak in March, driven by the late-season emergence of the H3 flu strain.
  • Despite high incidence rates, illness severity was lower this season than last, driven in part by a higher prevalence of the milder H1N1 flu strain (H3 is generally more severe).

Regional Differences

This past season was even more unusual when viewed by region. In fact, Florida is still experiencing elevated levels of cold & flu in May – more than 3% of Kinsa users there are still fighting a bug.

A few additional atypical findings:

  • The Northwest started out strong, experiencing relatively low illness levels throughout the typical season… until March. Just when many considered themselves “in the clear,” March saw illness levels as high as 9.2% for that region.

  • Kinsa has always seen that social distancing causes a drop in illness (when kids are out of school for the winter holidays, they don’t spread contagious illness as much). This was shown once again during the February polar vortex in the midwest – less people leaving their homes kept cold & flu spread at bay… for a while.

  • The Southeast experienced a different strain mix than the rest of the U.S. this year, with a significant H3 presence earlier in the season (yes, that’s the “bad” one).

Kinsa saw even greater anomalies as we sliced and diced our illness level information by city and State. If you’d like to dig in to learn more, feel free to contact [email protected] or view our public, interactive health map for yourself here.


How Kinsa calculates Illness levels

Kinsa aggregates infectious illness levels in real time through our broad network of smart thermometers and the connected Kinsa Health app. We use this information to estimate the percentage of the population afflicted with febrile illness (most commonly cold & flu) throughout the United States.

Kinsa Insights has become the earliest and most geo-precise signal for estimating infectious illness in the U.S., available to those who can help us take action to minimize the spread. External academics have validated Kinsa’s unprecedented localized illness detection and forecasting in peer-reviewed research. To learn more, visit us here.