The variant, NB.1.8.1, has been identified as the cause of Covid-19 resurgence in China and several other Asian countries. Experts in Europe are predicting a possible increase in cases there. A summer wave also could occur in the United States. According to the US Centers for Disease Control and Prevention, NB.1.8.1 already represents about one-third of new Covid-19 cases as of June 7. This is a significant increase from just a month before, when the new variant represented just 5% of new Covid-19 cases. … CNN: What are symptoms of N.B.1.8.1 infection? Wen: The symptoms appear to be similar to...