Seasonal influenza
Based on CDC and WHO guidance, checked against those sources on Oct 12, 2026. Educational information only — not a diagnosis or a substitute for a licensed healthcare professional.
Before and during travel
- Flu season differs by hemisphere: roughly October–March in the Northern Hemisphere and April–September in the Southern Hemisphere; in the tropics flu can circulate year-round.
- Check the influenza layer for your destination before you go.