When You Are No Longer Contagious with Influenza
Most adults are no longer contagious approximately 5-6 days after symptom onset, while children can remain infectious for up to 10 days, and immunocompromised individuals may shed virus for weeks to months. 1, 2
Contagious Period by Population
Healthy Adults
- Adults remain infectious from 1 day before symptoms develop through approximately 5-6 days after symptom onset. 1, 2, 3
- Viral shedding decreases rapidly by 3-5 days after illness onset in most adults, with most completing viral shedding by 5-7 days. 2
- The highest infectivity correlates with fever and respiratory symptoms, particularly in the first few days of illness. 2
Children
- Children can be infectious before symptoms begin and remain contagious for up to 10 days or more after symptom onset. 1, 2, 3
- Young children may shed virus several days before illness onset, making them particularly efficient transmitters. 2
Immunocompromised Individuals
- Severely immunocompromised persons may shed virus for weeks to months, requiring extended isolation precautions. 1, 2, 3
- This includes solid organ transplant recipients, patients on immunosuppressive therapy, and those with severe immune deficiencies. 1
Practical Isolation Recommendations
For Adults
- Isolation measures should continue for at least 5-6 days after symptom onset. 2
- You can consider ending isolation when you have been fever-free for at least 24 hours without fever-reducing medications AND respiratory symptoms have substantially improved. 1
For Children
- Isolation should be maintained for up to 10 days after symptom onset. 2
- This extended period accounts for prolonged viral shedding in pediatric populations. 2
For Hospitalized or High-Risk Patients
- Isolation using Standard and Droplet Precautions should continue until hospital discharge, or until signs and symptoms have resolved and the patient has been afebrile for at least 24 hours. 1
- For immunocompromised patients, consider maintaining isolation until documentation of a negative influenza test, as prolonged viral shedding is common. 1, 2
Important Caveats
Symptom Duration vs. Contagiousness
- Cough and malaise can persist for more than 2 weeks even after the infectious period ends, so ongoing symptoms do not necessarily mean you remain contagious. 2
- Uncomplicated influenza typically resolves after 3-7 days for most people. 2
Effect of Antiviral Treatment
- If treated with neuraminidase inhibitors (oseltamivir, zanamivir) within 48 hours of symptom onset, return to activities can be considered after completing 5 days of therapy, provided fever has resolved and respiratory symptoms have improved. 1
- Early antiviral treatment may reduce the duration of viral shedding, though this is not definitively established. 4, 5
Transmission Risk Factors
- The incubation period is 1-4 days, with an average of 2 days, meaning you are contagious before you even know you're sick. 2, 3
- Influenza spreads primarily through respiratory droplets from coughing and sneezing, as well as contact with contaminated surfaces. 3
- The virus can survive on hard surfaces for 24-48 hours and on hands for approximately 3 hours. 1