The Centers for Disease Control and Prevention has decided to postpone its session on nuclear attack preparedness next week. Much attention had been drawn to the timing of the agency’s session, which was publicized just days after President Trump touted the size of his nuclear button compared with North Korea’s.

Late Friday afternoon, the C.D.C. announced that it had changed its mind about next Tuesday’s topic, making a last-minute revision to reflect concerns about cases of severe flu.

“To date, this influenza season is notable for the sheer volume of flu that most of the United States is seeing at the same time, which can stress health systems,” the agency said. “The vast majority of this activity has been caused by influenza A H3N2, associated with severe illness in young children and people 65 years and older.”

Kathy Harben, a spokeswoman for the agency, said the Tuesday session would now address guidance for health professionals on trying to reduce the spread of the flu and to help with shortages of antiviral medicines in some hard-hit areas.