Donald Trump reportedly intends to seal off the US-Mexican border by invoking a public health emergency. The president-elect’s advisers have spent months searching for a disease that will allow them to justify closing the border using emergency health powers, The New York Times reports.

President-elect Donald Trump’s transition team is reportedly planning to reimplement Title 42, a border restriction used to block migrants from entering the United States due to public health concerns—but are still searching for the right disease to justify the policy.