The deadly coronavirus may have circulated in the US as early as December, about a month earlier than believed by the US CDC, according to researchers with UCLA. Their study, published last Thursday in the Journal of Medical Internet Research, found a statistically significant increase in clinic and hospital visits by patients who reported respiratory illnesses as early as the week of December 22. The first known case of Covid-19 in the US was thought to be a patient in Washington who had visited Wuhan, China, according to the CDC. The case was reported in January.