The United States reported a record number of new coronavirus cases as it headed into a holiday weekend. Health officials and experts attribute the rise in cases to reopenings across the country, uneven use of masks and increased travel. Three experts discuss what they have learned about coronavirus transmission during reopenings – and urge caution over the upcoming holiday weekend.

Where has reopening in the US been successful and where has it led to a surge in cases?

Saskia Popescu: Washington state reopened over the course of several months. In Arizona, where I live, we started allowing elective surgery…