As director general of the World Health Organization (WHO), navigating uncertainty is part of Tedros Ghebreyesus’ job. Health threats don’t give warnings, and the viruses and pathogens responsible for them aren’t always predictable.

But even he was surprised by President Donald Trump’s executive order on Jan. 20, Trump’s first day in office, announcing the U.S. was immediately withdrawing from the WHO and would cease communication with the organization. Most importantly, it would send no further funds, including what it owed for the 2024-2025 period. Ghebreysus was in Tanzania at the time, helping officials there manage an outbreak of Marburg virus (kin to Ebola) that killed the handful who were infected. While Trump had also attempted to withdraw from the WHO during his first term, there was no indication that he would continue those efforts—especially so soon. “There was no heads up,” Ghebreyesus says of the decision. He learned about it while watching the evening news.

The next day, at a planned meeting with international health agencies to discuss the Marburg situation, the U.S. ambassador was absent. “They started to enforce the order immediately,” Ghebreysus says. He still has not heard from Trump.