Matthew Herder and colleagues call for broader mobilisation to avoid the deaths and morbidity in low and middle income countries likely to result from recent US policy changes Announcing the United States’ withdrawal from the World Health Organization on his first day in office,1 and cutting a range of aid programmes in the weeks that followed, President Donald Trump is taking actions that are dire for global health. Treatments and related services in low and middle income countries for some conditions, such as HIV, rebounded in late 2025, showing the resilience of organisations most affected by US cuts.2 In addition, the US Congress protected one year of funding for global health with the passage of appropriations legislation in early 2026.34 Nevertheless, multiple estimates predict reduced US funding will lead to millions of deaths by 2030.5678 If the Trump administration follows through on its threat to halt funding for Gavi, the Vaccine Alliance,9 alter the US childhood vaccination schedule, and fundamentally change its approach to pandemic preparedness as part of its America First global health strategy,10 vaccine preventable diseases and deaths are likely to resurge, both in the US and abroad.11 Further, ceasing US funding for dozens of additional United Nations agencies, including UN Women and the UN Population Fund, threatens to end services that support sexual rights and reproductive health in more than 150 countries.1213 The US’s actions (table 1) are in flux. But taken together we argue that they constitute a public health emergency of international concern (PHEIC) under international law. And they warrant a swift response by WHO and the international community to spur country level and regional responses, reduce the spread of disease, and avert thousands more deaths. View this table: Table 1 US actions directly harmful to global …