Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript. In Seoul, South Korea, workers at a building where 46 people were confirmed to have coronavirus, wait in line for testing on 10 March.Credit: Jung Yeon-Je/AFP/Getty Diagnostic tests for COVID-19 have loomed large in the ongoing coronavirus pandemic as an essential tool to track the spread of the disease. The World Health Organization (WHO) has repeatedly urged health agencies to make testing for the novel coronavirus a top priority in their response to the pandemic, but the international response has been uneven. A combina...