The strain of COVID-19 virus that was circulating in the United States and Europe during the first wave of the pandemic may have been particularly infectious because the most common first symptom was likely a cough, according to a study.

The study suggests that people infected with what was the world’s most infectious strain of COVID-19 in May 2020, and the most dominant strain in the U.S. two months later, were likely to experience a cough as their first symptom, followed by fever.

To continue reading this story, click here.