They're everywhere! Lots of articles on COVID19 at the CDC, including early releases.   Here's one dated June 2020: Identifying and Interrupting Superspreading Events—Implications for Control of Severe Acute Respiratory Syndrome Coronavirus 2 Thomas R. Frieden and Christopher T. Lee Author affiliations: Resolve to Save Lives, New York, New York, USA Resolve to Save Lives received $225 million from Bloomberg Philanthropies, the Bill & Melinda Gates Foundation, and Gates Philanthropy Partners, which is funded with support from the Chan Zuckerberg Foundation. They're everywhere!