From the Guidelines
You can test positive for COVID-19 for up to 33 days after symptom onset, and in some cases, even up to 90 days after infection with PCR tests. The duration of a positive COVID-19 test result varies depending on the type of test used, with PCR tests detecting viral genetic material for a longer period than rapid antigen tests, which detect viral proteins 1. According to an observational analysis of 150 patients, the average time to transition from RT-PCR positive to negative was 24 days after symptom onset, and 10% of patients remained positive even 33 days after symptom onset 1. It's essential to note that a positive test result does not necessarily indicate active infection or contagiousness, especially after 10 days from symptom onset if symptoms are improving and fever has resolved without medication for 24 hours 1.
Some key points to consider:
- PCR tests can detect tiny fragments of viral RNA that remain in the body but don't indicate active infection 1
- Rapid antigen tests typically show positive results for a shorter period, usually 5-10 days, and better correlate with when you're actually contagious 1
- Immunocompromised individuals may shed virus and test positive for longer periods 1
- After hospital discharge, patients should be kept in isolation at least until 14 days have passed since the date of their first positive COVID-19 diagnostic test, and further isolation with regular health monitoring should be considered for up to 4 weeks 1
It's crucial to prioritize precautions to avoid infection transmission, even after recovery, to protect family members and the community from infection and further spread of SARS-CoV-2 1.
From the Research
Duration of COVID-19 Positivity
- The duration of COVID-19 positivity can vary depending on several factors, including the type of test used, the severity of symptoms, and the individual's immune response.
- According to a study published in 2021 2, antigen tests can detect current SARS-CoV-2 infection, but their sensitivity varies considerably between studies, ranging from 0% to 94%.
- The same study found that the average sensitivity of antigen tests was 56.2% (95% CI 29.5 to 79.8%) and average specificity was 99.5% (95% CI 98.1 to 99.9%).
- Another study published in 2020 3 reported that the sensitivity of antigen tests varied across studies, with an average sensitivity of 56.2% (95% CI 29.5 to 79.8%) and average specificity of 99.5% (95% CI 98.1 to 99.9%).
Factors Affecting Duration of Positivity
- The duration of COVID-19 positivity can be affected by several factors, including:
- Symptom severity: A study published in 2021 2 found that antigen test sensitivity was higher in the first week after symptom onset (78.3%, 95% CI 71.1% to 84.1%) than in the second week of symptoms (51.0%, 95% CI 40.8% to 61.0%).
- Viral load: The same study found that antigen test sensitivity was higher in individuals with higher viral loads (Ct values ≤25) (94.5%, 95% CI 91.0% to 96.7%) than in those with lower viral loads (Ct values >25) (40.7%, 95% CI 31.8% to 50.3%).
- Test type: A study published in 2020 3 reported that rapid molecular assays had higher sensitivity (95.2%, 95% CI 86.7% to 98.3%) and specificity (98.9%, 95% CI 97.3% to 99.5%) than antigen tests.
Treatment and Duration of Positivity
- The duration of COVID-19 positivity can also be affected by treatment, including antiviral medications and monoclonal antibodies.
- A study published in 2023 4 found that remdesivir and monoclonal antibodies reduced the risk of severe COVID-19 in hospitalized patients, particularly in those with immunocompromised hosts.
- Another study published in 2023 5 reported that early treatment with remdesivir alone or in combination with monoclonal antibodies prevented severe COVID-19 in patients with mild/moderate disease at high risk of progression.