The United States is preparing to issue guidance on reducing “unnecessary” testing for Covid-19 as it works to reduce turnaround times for tests, a senior US health official said on Thursday.

Details of the guidance are still being hammered out but it would be aimed partly at discouraging Covid-19 patients who have completed home quarantine from getting retested before returning to work or school, said Brett Giroir, assistant secretary for health at the US Department of Health and Human Services.