How long are individuals with COVID-19 (Coronavirus Disease 2019) typically infectious for?

COVID-19 Infectious Period Duration

Individuals with COVID-19 are typically infectious for up to 10 days from symptom onset in mild-to-moderate cases, though immunocompromised patients and those with severe disease may remain infectious for longer periods. 1

General Infectious Period Guidelines

Typical Cases (Mild-to-Moderate Illness)

• Infectious period begins 2-3 days before symptom onset 2
• Peak infectiousness occurs approximately 1 day before to 2-3 days after symptom onset 3
• Infectious virus is typically not detectable after 8-10 days from symptom onset 3
• PCR tests may remain positive for up to 30 days, well after the person is no longer infectious 3

Special Populations

• Severe or Critical COVID-19: Infectious virus may be isolated up to 32 days in some cases 4
• Immunocompromised Patients: May shed infectious virus for up to 20 days 4
• Asymptomatic Individuals: Should be considered infectious for at least 10 days after a positive test 1

Recent Evidence on Omicron Variant

A 2023 study of healthcare workers infected with the Omicron variant found:

• 13.5% of all cases still had positive viral cultures (indicating potential infectiousness) at day 10
• 11% of symptom-free cases still had positive viral cultures at day 10
• By day 14, viral culture positivity dropped to 8% overall and 5% in symptom-free cases 5

Recommended Isolation Guidance

The CDC recommends:

1. Wait at least 10 days since symptoms first appeared
2. Be fever-free for at least 24 hours without fever-reducing medications
3. Experience significant improvement in other COVID-19 symptoms 1

Factors Affecting Infectious Period

• Disease Severity: More severe cases may have longer infectious periods 4
• Immune Status: Immunocompromised individuals may remain infectious longer 1, 4
• Age: Elderly patients may require longer isolation periods 1
• Variant: Different variants may have different infectious periods, with recent evidence suggesting Omicron may have longer infectious periods in some cases 5

Common Pitfalls to Avoid

1. Relying solely on PCR testing: PCR tests can remain positive for weeks after a person is no longer infectious 3
2. Ending isolation too early: At least 10 days from symptom onset is recommended for most cases 1
3. Assuming all cases have the same infectious period: Individualized assessment is needed for severe cases and immunocompromised patients 1, 4
4. Overlooking asymptomatic transmission: Approximately 24% of all transmission may come from individuals who never develop symptoms 2

Clinical Decision Algorithm

1. For mild-moderate cases: Isolate for 10 days from symptom onset, ensure fever-free for 24 hours, and symptoms improving
2. For severe cases or immunocompromised patients: Consider extended isolation (up to 20 days) and possibly viral culture testing if available
3. For asymptomatic cases: Isolate for 10 days from first positive test
4. For healthcare workers caring for high-risk patients: Consider extending isolation to at least 10 days regardless of symptom resolution 5

The evidence consistently shows that while most individuals are no longer infectious after 10 days, certain populations may require longer isolation periods to prevent transmission and reduce morbidity and mortality.