The United States had its first coronavirus superspreader event during a two-day conference in Boston organized by the biotech company Biogen in February. Genetic testing has revealed that what began with 99 people who became infected with SARS-CoV-2 at the event, another 205,000–300,000 cases subsequently resulted as the attendees returned home to 29 states and several other countries, carrying the virus with them, according to a study published in Science on December 10. A national database of SARS-CoV-2 genomes and contact tracing has allowed the authors to track which strains were being transmitted. As reports, the proportion of the pandemic attributed to the conference is roughly 1.6 percent of all US COVID-19 cases.