How long is Covid-19 (Coronavirus disease 2019) contagious?

COVID-19 Contagious Period

Most people with COVID-19 can discontinue isolation 10 days after symptom onset (or positive test if asymptomatic), provided they have been fever-free for at least 24 hours without antipyretics and other symptoms have improved. 1

Standard Isolation Duration

The contagious period for COVID-19 follows a predictable pattern based on viral clearance:

• Isolation should last 10 days from symptom onset for most patients with COVID-19 1
• Patients must be fever-free for ≥24 hours without fever-reducing medications 1
• Other symptoms must show improvement before ending isolation 1
• For asymptomatic individuals, the 10-day period begins from the date of the first positive test 1

Viral Clearance Timeline

The sequence of viral clearance provides insight into when patients are no longer infectious:

• Infectious virus (measured by viral culture) clears first, typically within 5-9 days after symptom onset 2
• Rapid antigen tests turn negative next, serving as a reliable indicator that infectious virus is no longer being produced 2
• PCR tests remain positive longest, often for weeks after a person is no longer contagious 2, 3
• Viral shedding in the upper respiratory tract continues beyond 10 days in severe COVID-19 cases 4

Early Release from Isolation (5-Day Option)

Some patients may end isolation after 5 days under specific conditions:

• Isolation can end after 5-9 days if symptoms are resolving or absent 5
• A negative rapid antigen test result is required to end isolation early 5
• After 5 days of isolation, approximately 54% of patients still test positive on antigen tests, indicating ongoing infectiousness 5
• Patients ending isolation before 10 days should wear a well-fitting mask around others through day 10 5

Factors Affecting Contagious Period

Several factors influence how long someone remains contagious:

• Symptomatic infection prolongs contagiousness compared to asymptomatic infection 5
• Previous COVID-19 infection shortens the contagious period 5
• COVID-19 vaccination (primary series) reduces duration of infectiousness 5
• Severe disease or immunosuppression may extend the contagious period, requiring case-by-case assessment 1
• Age and symptom duration at presentation correlate with prolonged PCR positivity, though not necessarily prolonged infectiousness 3

Post-Isolation Precautions

Even after meeting isolation criteria, continued precautions are warranted:

• Patients should wear masks around others through day 10 after symptom onset or positive test 5
• Most patients can return to work after meeting the 10-day criterion plus symptom improvement and fever resolution 1
• Patients are unlikely to be infectious after meeting standard isolation criteria 1

Special Populations

Certain groups require modified isolation approaches:

• Severely ill patients or those on immunosuppressive medications need individualized isolation duration determination 1
• Healthcare workers and high-risk settings may require negative testing before return to work 4
• Some patients show positive RT-PCR tests beyond 14 days, but this does not indicate ongoing infectiousness or affect clinical outcomes 3
• Surgical COVID-19 patients should remain isolated for at least 2 weeks from first positive test until negative RT-PCR is obtained 4

Common Pitfalls

Do not rely on PCR testing to determine end of contagious period - PCR tests can remain positive for weeks after infectious virus has cleared 2, 3. The median time to PCR negativity is 9 days after symptom onset, but this does not correlate with infectiousness 3.

Rapid antigen tests are superior to PCR for determining infectiousness - a negative rapid antigen test reliably indicates loss of infectious virus and ability to end isolation 2.