"We are asking the American public to prepare for the expectation that this might be bad," said Dr Nancy Messonnier of the National Center for Immunisation and Respiratory Diseases in a conference call with reporters on Tuesday.
"It's not so much a question of if this will happen in this country any more but a question of when this will happen," she said, adding: "Disruption to everyday life might be severe."
https://www.bbc.com/news/world-us-canada-51637481