GENEVA — The race to choose the head of the World Health Organization is a test of who will shape global health after America’s retreat: Europe, rising powers in Asia or increasingly influential Gulf states. Countries will decide next year who should lead the WHO after Tedros Adhanom Ghebreyesus’ second term ends in August 2027, handing the winner an agency recovering from the loss of its biggest donor, facing calls for institutional reform and the increasing threat of another global health