An outbreak of the Coronavirus on the U.S. mainland is imminent, according to officials with the Center for Disease Control (CDC).

As of February 25, 53 cases have been diagnosed, 39 of which concern Americans who have been repatriated from abroad. Approximately 2,500 people have died from the virus worldwide, the majority of who are Chinese.

“It’s not so much of a question of if this will happen in this country any more [sic] but a question of when this will happen,” said Dr. Nancy Messonnier, the director of the National Center for Immunization and Respiratory Diseases (NCIRD).

The CDC is gearing up to defend the country against the deadly virus. And U.S. health officials seem quite aggressive in their protective measures.