WASHINGTON — After weeks of conflicting signals from the Trump administration about the coronavirus, the government’s top health officials decided late last month that when President Trump returned from a trip to India, they would tell him they had to be more blunt about the dangers of the outbreak.

If he approved, they would level with the public.

But Dr. Nancy Messonnier, the director of the National Center for Immunization and Respiratory Diseases at the Centers for Disease Control and Prevention, got a day ahead of the plan. At noon on Feb. 25, just as Mr. Trump was boarding Air Force One in New Delhi for his flight home, she told reporters on a conference call that life in the United States was about to change.

“The disruption to everyday life might be severe,” she said. Schools might have to close, conferences could be canceled, businesses might make employees work from home. She had told her own children, she said, to prepare for “significant disruption to our lives.”