Experts worry about how US will see next COVID surge coming

              FILE - A second grade student is give a at-home COVID-19 test at H.W. Harkness Elementary School in Sacramento, Calif., Friday, Feb. 11, 2022. The Sacramento City Unified School District began distributing the tests to elementary and middle school students, and families are to submit the results before returning to class. (AP Photo/Rich Pedroncelli)
              FILE - Firefighters from the Marins-Pompiers of Marseille extract samples of sewage water at a retirement home in Marseille, southern France, Thursday Jan. 14, 2021, to trace concentrations of COVID-19 and the highly contagious variant that has been discovered in Britain. As coronavirus infections rise in some parts of the world, experts are watching for a potential new COVID-19 surge in the U.S. — and wondering how long it will take to detect. (AP Photo/Daniel Cole)
            Emily Lu, a student in the environment science graduate program at Ohio State, tries to extract ribonucleic acid (RNA) from wastewater samples to test for fragments of the coronavirus, March 23, 2022 at a school lab in Columbus, Ohio. (AP Photo/Patrick Orsagos) Graduate program students Emma Lancaster, right, Emily Lu, center, and Fan He, left, work to extract remnants of COVID-19 in wastewater samples, March 23, 2022 at a school lab at the Ohio State University in Columbus, Ohio. (AP Photo/Patrick Orsagos)