Cautious Optimism as National Illness Levels Trend Downward

This chart shows ILI from December 24, 2020 until January 19, 2021

Three main indicators informing Kinsa’s early warning system for spreading illness are decreasing on a national level— a promising sign that COVID-19 cases will continue to drop across the U.S.

These indicators are:

• Influenza-like Illness (ILI), the percentage of the population currently experiencing a fever

• Rate of transmission (Rt), an indicator of how many people become infected on average from each sick individual. If Rt is above 1, the number of people experiencing fevers will increase.

• Long-duration fevers, similar to ILI but only including fevers lasting at least 72 hours, which indicate more severe illness.

Each of these measures rose after the holidays from expected dips around Christmas because fewer people use their smart thermometers on holidays. ILI in particular showed the steepest climb after Christmas, reflecting the expected holiday surge. 

However, beginning in mid-January, these metrics began to decrease on average, pointing to an overall decline in forecasted cases. Last week, we projected 8 states to have stable or decreasing cases, but this week, we are projecting 25 states with this positive trend.

While this is good news, there are a few caveats:

• Because Rt was elevated, we still expect this to translate to some increases in ILI and long-duration fevers.

• The downward trends aren’t universal. In fact, much of the upper Midwest is showing elevated Rt. In particular, in Minnesota,  Rt was below 1.0 in November, but this month it has skyrocketed in the region.

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