Guillain-Barré syndrome (GBS) causes progressive muscle weakness and paralysis (complete inability to use a particular muscle or muscle group), which develops over days or up to four weeks, and lasts several weeks or even months.

GBS typically occurs in a patient who has just recovered from a seemingly uncomplicated viral infection, most commonly cytomegalovirus, herpes, Epstein-Barr virus, or viral hepatitis. GBS may also follow a gastrointestinal infection with the bacteria Campylobacter jejuni, in which case the GBS is particularly severe. About 5% of GBS cases follow a surgical procedure. Individuals with lymphoma, systemic lupus erythematosus, or AIDS have a higher-than-normal risk of GBS. Other GBS patients may have recently received an immunization, while still others have no known preceding event. In 1976-77, there was a vastly increased number of GBS cases among people recently vaccinated against Swine flu. The reason for this has never...