If the virus has been spreading undetected in Washington since mid-January, that could mean that anywhere from 150 to 1,500 people may have it, with about 300 to 500 people the most likely range, said Dr. Mike Famulare, a principal research scientist at the Institute for Disease Modeling in Bellevue, Wa., who performed the analysis. These people “have either been infected and recovered, or currently are infected now,” he said.