"This extreme drop is exactly what we would hope and expect with the measures currently in place."
As governments around the world have pushed their citizens away from populated places to slow the spread of Covid-19, they may not have realized that they were also combatting other infectious diseases, such as the seasonal flu.
But they have been, according to data from Kinsa Health, a company that has sold or given away more than 1 million smart thermometers in the US. Kinsa collects anonymized thermometer readings (via its app, which users connect to the device) from its active user base to estimate the share of people that are ill in different geographies. By comparing current thermometer readings to historical trends, researchers have used Kinsa’s data to predict flu outbreaks weeks before the Centers for Disease Control and Prevention’s surveillance program, which uses hospitalization records.
Recent data clearly show the spread of Covid-19. On March 19, the share of Americans with temperatures indicating they had flu-like symptoms was about 4.9% when it typically would be expected to be about 4.0%. This was likely a result of the spread of Covid-19, according to Kinsa’s researchers.
But by March 23, it was down to 3.3%, when it would typically be at 3.7% (the share of fevers decreases quickly at this time of year because of the end of winter).
The drop—from 0.9% above typical flu-like illness rates to 0.4% below—in just four days is the largest one Kinsa has ever observed in such a short period of time, according to Kinsa CEO Inder Singh. “There is no known precedent for this type of extensive social distancing in recent time,” said Singh. “We have nothing to compare this to, but this extreme drop is exactly what we would hope and expect with the measures currently in place.”