Guillain-Barré syndrome (GBS) is an acute, frequently severe, and fulminant polyradiculoneuropathy that is autoimmune in nature in which your body’s immune system attacks your nerves.  Causes GBS appears days or weeks after a respiratory or digestive tract infection. COVID-19 virus Swine influenza vaccine Recent surgery Vaccination Influenza vaccinations Childhood vaccinations  Rabies vaccine Most commonly, infection with