The US Food Safety and Inspection Service recommends cooking burgers to an internal temperature of at least 71.1 °C (160 °F).
See the FSIS website for more information on how to store and cook ground beef safely
One of the bactieria commonly associated with food poisoning from undercooked hamburgers and other ground beef-products is Enterohemorrhagic E. coli, which can cause something called Hemolytic Uremic Syndrome which in turn can cause kidney failure and even death.
US Department of Agriculture, Food Safety and Inspection Service “Ground Beef and Food Safety” https://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/meat-preparation/ground-beef-and-food-safety/ct_index last accessed 6. february 2021
Johns Hopins Medicine “Enterohemorrhagic Escherichia coli” https://www.hopkinsmedicine.org/health/conditions-and-diseases/enterohemorrhagic-escherichia-coli last accessed 6. february 2021
Mayo Clinic “Hemolytic uremic syndrome (HUS)” https://www.mayoclinic.org/diseases-conditions/hemolytic-uremic-syndrome/symptoms-causes/syc-20352399 last accessed 6. february 2021
BBC “Boy poisoned by E. coli-infected beef in 2011 dies in France” https://www.bbc.com/news/world-europe-49716578 published 16. september 2019, last accessed 6. february 2021