Does it spread more easily? Make people sicker? Mean that treatments and vaccines won’t work? Questions are multiplying as fast as new strains of the coronavirus, especially the one now moving through England. Scientists say there is reason for concern but that the new strains should not cause alarm. “There’s zero evidence that there’s any increase in severity” of COVID-19 from the latest strain, the WHO’s emergencies chief, Dr. Michael Ryan said Monday. “We don’t want to overreact,” the U.S. government’s top infectious disease expert, Dr. Anthony Fauci, told CNN.