| Prevalence | 1–2 per 100,000 person-years worldwide; no significant geographic variation |
| Age | All ages affected; incidence increases with age (highest in adults >50 years) |
| Sex | Slight male predominance (M:F ratio ~1.5:1) |
| Seasonal variation | Minor peaks in winter (respiratory triggers) and summer (enteric triggers) |
| Mortality | 3–7% even with optimal treatment; higher in elderly and those requiring mechanical ventilation |
| Disability | ~20% of patients have persistent significant disability at 1 year; ~60% have full motor recovery |
| Preceding infection | Identified in 60–70% of cases |
| Databases | OMIMOrphanetClinicalTrialsPubMed |