Case research particulars leukemia affected person who shed infectious SARS-CoV-2 for not less than 70 days

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Case study details leukemia patient who shed infectious SARS-CoV-2 for at least 70 days

A scanning electron microscope image of SARS-CoV-2 obtained from a nasopharyngeal swab of an immunocompromised patient and cultured with VERO-E6 cells. Image credit: NIAID-RML

The majority of people infected with SARS-CoV-2 appear to be actively shedding the infectious virus for about 8 days, but there is a wide range of variation from person to person. Understanding how long people can actively remain infected is important as it provides new details about a disease and virus that are not yet well understood and that will influence public health decisions. Researchers report an unusual case of a woman with leukemia and low antibody counts who was infected with the coronavirus for at least 105 days and infectious for at least 70 days, all the while remaining asymptomatic, in Cell magazine on Nov.

"At the beginning of this study, we really didn't know much about the duration of the virus shedding," says senior author Vincent Munster, a virologist at the National Institute for Allergies and Infectious Diseases. "As this virus continues to spread, more people will become infected with a range of immunosuppressive disorders, and it is important to understand how SARS-CoV-2 behaves in these populations."

Munster, an expert on emerging infectious diseases, began publishing research on SARS-CoV-2 in January. He was contacted in April by infectious disease specialist Francis Riedo, a co-author of the study, about a patient in Kirkland, Washington, who was infected very early in the COVID-19 pandemic. Riedo's patient had done numerous positive PCR tests for the virus over a period of weeks and he wanted to know if she was still shedding viruses.

The patient, a 71 year old female, was immunocompromised from chronic lymphocytic leukemia and acquired hypogammaglobulinaemia. She never showed any symptoms of COVID-19. She was found to be infected with the virus when she was checked for severe anemia after being admitted to the hospital. Her doctors realized that she was living in a rehab facility where a major outbreak was occurring.

Case study details Leukemia patient who shed infectious SARS-CoV-2 for at least 70 days
A scanning electron microscope image of SARS-CoV-2 obtained from a nasopharyngeal swab of an immunocompromised patient and cultured with VERO-E6 cells. Image credit: NIAID-RML

Munster's lab at NIAID's Rocky Mountain Laboratories in Hamilton, Montana, began examining samples taken regularly from the patient's upper airways. They found that the infectious virus was still present for at least 70 days after the first positive test, and the woman didn't get rid of the virus completely until after day 105. "This was something we expected to happen, but it was never reported to have happened before," says Munster.

Investigators believe the patient remained contagious for so long because her weakened immune system never allowed her to have a reaction. Blood tests showed that her body was never able to make antibodies. She was once treated with convalescent plasma, but Munster does not believe that the treatment had any effect due to the low concentration of antibodies. Despite her inability to develop an antibody response, she never evolved COVID-19.

The team performed a thorough sequencing of all virus samples received from the patient to determine how the virus might have changed over the course of the patient's infection. Samples taken at different times showed different dominant gene variants. However, the researchers do not believe that these mutations played a role in the persistence of the virus as they saw no evidence of natural selection. Selection would have been implied if any of the variants had given the virus a survival advantage and become the dominant variant, but none of them did. They also tested whether or not the mutations affected the ability or speed of the virus to replicate and found no differences.

Munster says this is, as far as he knows, the longest case anyone has been actively infected with SARS-CoV-2 while remaining asymptomatic. "We have seen similar cases of influenza and respiratory syndrome in the Middle East, which is also caused by a coronavirus," he said. "We expect more reports like ours to be published in the future."

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More information:
Victoria A. Avanzato et al. Case study: prolonged infectious SARS-CoV-2 breakdown in an asymptomatic immunocompromised cancer patient. Cell. Published: November 04, 2020 DOI: doi.org/10.1016/j.cell.2020.10.049

Journal information:
cell

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Case study details Leukemia patient who has shed infectious SARS-CoV-2 for at least 70 days (2020, November 4th)
accessed on November 4, 2020
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