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Patients who are profoundly immunosuppressed after extensive cancer treatment, and who fall ill with COVID-19, can shed viable SARS-CoV-2 virus for at least 2 months after symptom onset, and may need extended periods of isolation.

Live-virus shedding was detected in 18 patients who had undergone hematopoietic stem cell transplants or chimeric antigen receptor (CAR) T-cell therapy and in 2 patients with lymphoma.

The finding was reported December 1 in a research letter in the New England Journal of Medicine.

Individuals who are otherwise healthy when they get COVID-19 are "no longer infectious after the first week of illness," commented lead author Mini Kamboj, MD, chief medical epidemiologist, Memorial Sloan Kettering Cancer Center, New York City.

"We need to keep an open mind about how [much] longer immunocompromised patients could pose an infection risk to others," she added.

Kamboj told Medscape Medical News that her team's previous experience with stem cell transplant recipients had suggested that severely immunocompromised patients shed other viruses (such as respiratory syncytial virus, parainfluenza, and influenza) for longer periods of time than healthy controls.

Based on their latest findings, investigators suggest that current guidelines for COVID-19 isolation precautions may need to be revised for immunocompromised patients. Even if only a small proportion of patients with cancer who have COVID-19 remain contagious for prolonged periods of time, "it's a residual risk that we need to address," Kamboj said.

Kamboj also suggested that physicians follow test-based criteria to determine when a patient undergoing transplant can be released from isolation.

For this study, the investigators used cell cultures to detect viable virus in serially collected nasopharyngeal and sputum samples from 20 immunocompromised patients who had COVID-19 (diagnosed with COVID-19 between March 10 and April 20).

Of these 20 patients, 15 were receiving active treatment or chemotherapy. Eleven out of the group developed severe COVID-19 infection.

In total, 78 respiratory samples were collected. "Viral RNA was detected for up to 78 days after the onset of symptoms," researchers report, "[and] viable virus was detected in 10 of 14 nasopharyngeal samples (71%) that were available from the first day of laboratory testing."

Five patients were followed up, and from these patients, the team grew virus in culture for up to 61 days after symptom onset. Two among this small group of 5 patients had received allogenic hematopoietic stem cell transplantation and one patient had been treated with CAR T-cell therapy within the previous 6 months. Interestingly, this patient remained seronegative for antibodies to the coronavirus.

For 11 patients, the team obtained serial sample genomes, and found that "each patient was infected by a distinct virus and there were no major changes in the consensus sequences of the original serial specimens or cultured isolates." These findings were consistent with persistent infection, they note.

The authors have disclosed no relevant financial relationships.

N Engl J Med. Published online December 1, 2020. Research letter

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Extended Virus Shedding After COVID in Some Patients With Cancer - Medscape