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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 infectious risk to others. However, whether this is true for SARS-CoV-2 infection has not been definitively established.

Typically, after the onset of illness, the detectable viral burden declines. After a week or more, anti-SARS-CoV-2 immunoglobulin becomes detectable and antibody titers rise. Some of these antibodies may prevent the virus from infecting cells in cell culture. The decline in viral burden is associated with decreased ability to isolate live virus. Efforts to isolate live virus from upper respiratory tract specimens have been unsuccessful when specimens are collected more than 10 days after illness onset.

Persons who have tested persistently or recurrently positive for SARS-CoV-2 RNA have shown stable or improving signs of illness. 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. In addition, there is no evidence that clinically recovered persons with persistent or recurrent detection of viral RNA have transmitted COVID-19 to others.

Despite encouraging observations to date, it’s not possible to conclude that persons with persistent or recurrent detection of SARS-CoV-2 RNA are no longer infectious. There is no firm evidence yet that the antibodies that develop in response to infection are protective. If these antibodies are protective, it’s not known what antibody titers are associated with protection from reinfection.

Based on these data and experience with other viral infections, most persons recovered from COVID-19 who test persistently or recurrently positive by RT-PCR are likely no longer infectious. Additionally, the magnitude and persistence of the immune response following recovery may vary among individuals, with factors such as age potentially influencing protection. Based on limited available data, determinations must be made on a case-by-case basis as to whether recovered persons with persistently detectable SARS-CoV-2 RNA are potentially infectious to others and should continue to be in home isolation and excluded from work, school, or other group settings. Such determinations are typically made in consultation with infectious diseases specialists and public health officials, after review of available information (e.g., medical history, time from initial positive test, RT-PCR Ct values, and presence of COVID-19 signs or symptoms).