Short answer: Most people with influenza A are contagious from about 1 day before symptoms start and remain contagious for about 5–7 days after becoming sick, with the potential for longer contagiousness in young children or people with weakened immune systems. Always err on the side of caution and stay home until at least 24 hours after fever resolves without fever-reducing medication. Details
- Contagious window: Typically from 1 day before symptoms appear to 5–7 days after illness begins. Some people, especially kids or those with weakened immune systems, may shed the virus longer.
- Peak contagiousness: Most likely to spread the virus during the first 3 days of illness, when symptoms are most pronounced and coughing/sneezing generate droplets.
- When to return to work or school: Stay home until you’ve been fever-free for at least 24 hours (without fever-reducing meds) and your symptoms are improving, as advised by health guidelines.
- Variation by age and health: Infants and people with compromised immune systems often remain contagious longer than healthy adults.
Tips to reduce spread
- Practice good hand hygiene and cover coughs and sneezes.
- Avoid close contact with others and stay home from work, school, or public activities during the contagious period.
- If you’re at higher risk for complications or have persistent or worsening symptoms, contact a healthcare provider.
If you’d like, I can tailor these timelines to your situation (age, underlying health conditions, fever status) and provide a checklist for when to rejoin activities safely.
