I found this at the Washington Post.

By simply counting coughs, a team of researchers found evidence that covid-19 may have been spreading in the United States weeks earlier than was previously suspected.

The team examined six years of electronic health records in Los Angeles, searching for reports with the word “cough,” a common covid-19 symptom. From this, they learned that respiratory failure hospitalizations spiked in late December last year and remained above historic levels for the next 10 weeks. “This is consistent with the growing body of data that suggests that there’s been community spread much earlier than we had anticipated,” one of the study's authors, an epidemiologist at the University of California at Los Angeles, told The Post.