Countries: Afghanistan, Haiti, Liberia, Malawi, Mozambique, Sierra Leone, Somalia, South Sudan, Uganda, United Republic of Tanzania, World Source: Center for Global Development The Trump administration’s recent actions on foreign aid are dramatically shifting the global health funding landscape and triggering a health financing crisis in many countries. The US is the largest global health funder, providing an estimated $12.4 billion each year. Nearly 70 percent of this ($8.5 billion) is allocated as bilateral health aid, which has been heavily disrupted by the administration’s actions. And for many of the lifesaving services supported by US assistance—from antiretroviral therapy and tuberculosis treatment to emergency care for mothers and newborns—even a temporary pause can have deadly consequences. These actions are also particularly concerning because other major global health donors, namely European governments, are slashing aid budgets and low- and middle-income countries (LMICs) are facing mounting debt pressures.In this blog, we conceptualise this as a health system shock, present a back-of-the-envelope assessment of LMICs that are most exposed, and discuss possibilities for short-term policy responses from other funders and LMIC governments, drawing lessons from the rapid global response to COVID-19.We find that 26 LMICs, with a combined total population of 1.38 billion, are both highly exposed to US global health aid cuts and highly fiscally constrained, meaning they are least able to adequately respond. Amid economic headwinds and shifting geopolitics, bilateral government donors as well as philanthropies and multilateral development banks may be unlikely to fill the entirety of the gap left by the US, at the necessary scale and speed. Prioritisation and agile support from funders to countries that are most exposed and least able to respond will be key.Which countries are exposed to US global health aid cuts and fiscally constrained?First, we consider how much US bilateral global health assistance each country receives. This encompasses funding implemented by USAID, the State Department, and other agencies, such as the Centers for Disease Control and Prevention, and which is spent primarily through US-based implementing partners. US multilateral contributions to global health initiatives such as the Global Fund and Gavi are excluded from the analysis.To assess the magnitude of the funding shock, we compare the total amount of US bilateral global health funding that a country received to domestic government expenditure on health in 2022. We drill down on countries that are “highly exposed” to funding cuts, defined as those where US bilateral global health assistance is equivalent to 10 percent or more of government health expenditure. We then investigate two indicators as a proxy of a country’s ability to respond: their World Bank income classification and their level of indebtedness. While a full fiscal space analysis for each country would yield a more detailed picture, this back-of-the-envelope approach is designed to rapidly identify priority countries that are “highly fiscally constrained” and are therefore, in urgent need of immediate intervention by external funders.