Coronavirus

Corona case study: 70-year-old woman with no symptoms was infectious for 70 days

Electron microscope image of SARS-CoV-2, from the swab of an immunocompromised patient.

NIAID-RML

What is the course of a Covid 19 illness? What symptoms does the virus trigger? And how contagious is it? There are still no clear answers to all of these questions, as the coronavirus can affect every individual person differently.

Now researchers are reporting in the journal “Cell” about another special case of Covid-19 infection: A 71-year-old woman suffering from leukemia shows no symptoms of Covid-19 after an initial positive corona test. However, even 70 days after her first positive test, she is still releasing infectious SARS-CoV-2 particles. It is the longest known case of asymptomatic infection.

The research team emphasizes that this is a case study, i.e. an individual case from which no generalizations can be drawn. Nonetheless, these data suggest that long-term shedding of the infectious virus in certain immunocompromised patients may be of concern. People with a weakened immune system – cancer patients or transplant recipients who take immunosuppressive drugs – seem to be able to shed the coronavirus for a long time.

“As the virus continues to spread, more and more people will become infected with immunosuppressive diseases. It is therefore important to understand how SARS-CoV-2 behaves in these population groups, ”says the virologist and co-author of the study Vincent Munster from the US National Institute of Allergy and Infectious Diseases.

In this case, the doctors discovered the woman’s infection by chance: on March 2, 2020, she was hospitalized for severe anemia related to her cancer and tested positive for the virus. She then tested positive 13 more times and still showed no symptoms until the virus 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 checked whether the extracted virus could still multiply and whether it could establish a productive infection after it was transferred to other cells – which was the case. Further experiments with the isolated virus also showed that genetic changes did not affect how quickly the virus reproduced.

Even if more research is needed, what is learned is important in providing adequate treatment and curbing virus transmission. The research team believes the woman remained infectious for so long because her weakened immune system never allowed her to trigger an appropriate response to the virus.

Researchers know that immunocompromised people shed common seasonal coronaviruses for weeks after infection. Studies of MERS and influenza have also shown that immunocompromised people still shed the virus that causes the disease for up to a month after infection.

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