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Electron microscope image of SARS-CoV-2 from the swab of an immunocompromised patient.
NIAID-RML
- In a new case study, the researchers describe a 71-year-old woman who was still emitting infectious SARS-CoV-2 particles 70 days after her first positive corona test.
- Even after 13 positive tests, the woman remained asymptomatic, that is, she had no symptoms. The research team suspects that the woman with leukemia has remained contagious for so long due to her weakened immune system.
- People with weakened immune systems – cancer patients or transplant patients taking immunosuppressive drugs – appear to have been able to spread the coronavirus for a long time.
What is the course of a Covid 19 disease? What symptoms does the virus trigger? And how contagious is it? There are still no clear answers to all these questions, as the coronavirus can affect every single person differently.
Researchers are now reporting another special case of Covid-19 infection in the magazine “Cell”: a 71-year-old woman with leukemia shows no symptoms of Covid-19 after an initial positive corona test. 70 days after its first positive test, however, it is still releasing infectious SARS-CoV-2 particles. It is the longest known case of asymptomatic infection.
The research team points out that this is a case study, i.e. an individual case from which no generalizations can be drawn. However, these data suggest that the long-term spread of the infectious virus may be a cause for concern in some immunocompromised patients. People with weakened immune systems – cancer patients or transplant patients taking immunosuppressive drugs – appear to be able to get rid of the coronavirus for a long time.
“As the virus continues to spread, more and more people will be infected with immunosuppressive diseases. It is therefore important to understand how SARS-CoV-2 behaves in these population groups, ”says virologist and study co-author Vincent Munster of the US National Institute of Allergy and Infectious Diseases.
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In this case, doctors accidentally discovered the woman’s infection: on March 2, 2020 she was hospitalized for severe anemia linked to her cancer and tested positive for the virus. She then tested positive 13 more times and still showed no symptoms until the virus was finally cleared from her system in mid-June.
In the 15 weeks of their Covid 19 infection, the researchers collected numerous throat swabs. Using the samples, they tested whether the extracted virus could still multiply and whether it could establish a productive infection after being transferred to other cells, as was the case. Further experiments with the isolated virus also showed that genetic changes did not affect how quickly the virus reproduced.
While more research is needed, what is learned is important in providing adequate treatment and curbing transmission of the virus. The research team believes the woman has been contagious for so long because her weakened immune system never allowed her to trigger an adequate response to the virus.
Researchers know that immunocompromised people lose common seasonal coronaviruses for weeks after infection. Studies on MERS and influenza have also shown that immunocompromised people still lose the virus that causes the disease up to a month after infection.
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