Are recovered persons with persistent positive test of COVID-19 infectious to others?
Whether the presence of detectable but low concentrations of viral RNA after clinical recovery represents the presence of potentially infectious virus is unknown. Based on experience with other viruses, it is unlikely that such persons pose an important infectious risk to others. However, whether this is true for SARS-CoV-2 infection has not been definitively established.
After the onset of illness, the detectable viral burden usually declines. After a week or more, anti-SARS-CoV-2 immunoglobulin becomes detectable and then antibody levels increase. Some of these antibodies may prevent the virus from infecting cells in cell culture. A decline in viral RNA is associated with a decreased ability to isolate live virus. For most patients with COVID-19, efforts to isolate live virus from upper respiratory tract specimens have been unsuccessful when specimens are collected more than 10 days after illness onset. Recovery of live virus between 10 and 20 days after symptom onset has been documented in some persons with severe COVID-19; in some cases, these persons were in an immunocompromised state.
Persons who have tested persistently or recurrently positive for SARS-CoV-2 RNA have, in some cases, had their signs and symptoms of COVID-19 improve. When viral isolation in tissue culture has been attempted in such persons in South Korea and the United States, live virus has not been isolated. There is no evidence to date that clinically recovered persons with persistent or recurrent detection of viral RNA have transmitted SARS-CoV-2 to others.
Despite these observations, it’s not possible to conclude that all persons with persistent or recurrent detection of SARS-CoV-2 RNA are no longer infectious. There is no firm evidence that the antibodies that develop in response to SARS-CoV-2 infection are protective. If these antibodies are protective, it’s not known what antibody levels are needed to protect against reinfection.
These data and experience with other viral respiratory infections indicate that most persons recovered from COVID-19 who test persistently or recurrently positive by RT-PCR are likely no longer infectious. Isolation and precautions may be discontinued for persons with COVID-19 10 days after symptom onset (the date on which symptoms first began, including non-respiratory symptoms), provided their fever has resolved for at least 24 hours, without the use of fever-reducing medications, and their other symptoms have improved. For some persons with severe or critical illness, or who are severely immunocompromised, isolation and precautions may be maintained for up to 20 days after symptom onset.
