An extraordinary percentage of people infected by the virus behind the ongoing deadly COVID-19 pandemic—up to 45 percent—are people who never show symptoms of the disease, according to the results of a Scripps Research analysis of public datasets on asymptomatic infections. Scrippssays that the findings, recently published in Annals of Internal Medicine, suggest that asymptomatic infections may have played a significant role in the early and ongoing spread of COVID-19 and highlight the need for expansive testing and contact tracing to mitigate the pandemic.