A 71-year-old woman in the US state of Washington was found to be transmitting SARS-CoV-2 coronavirus particles for 70 days after her initial infection, although she never showed the slightest symptom of Covid-19 during this time.

The woman has a weakened immune system, as she suffers from blood cancer (leukemia), as a result of which her body finds it very difficult to “cleanse” the virus.

Unprecedented case of contagion

Although scientists suspected that immunocompromised humans and those with a weakened immune system generally transmitted the coronavirus usually for longer than other vectors, no such case of 70-day transmissibility had ever been found internationally.

The US Centers for Disease Control and Prevention (CDC) estimates that people with an abnormal immune system are no longer infectious when they are about 20 days after their initial infection, but this does not always seem to be the case.

The researchers, led by virologist Vincent Munster of the US National Institute of Allergy and Infectious Diseases (NIAID), who published the paper in the journal Cell Biology, said that long-term elimination of infectious some patients with impaired immune systems”.

“As the coronavirus continues to spread, more people with immunosuppressive disorders will become infected, and this is important for understanding how SARS-CoV-2 behaves in these populations”

says Dr. Munster

The woman became infected at the end of February, at a clinic where she was treated for anemia due to her cancer, and was diagnosed with the coronavirus on March 2.

She has since undergone dozens of tests and the virus has been continuously detected in her body for 105 days, while infectious virus particles – capable of transmitting the disease to others – have been detected for at least 70 days. The inability of her immune system to “respond” to the virus was shown by the fact that there were no antibodies against it in her blood.

Patients are usually contagious for about eight days after the initial infection

Typically, patients with Covid-19 are contagious for about eight days after the initial infection. The previous longest case was a patient who was found to be infectious for 20 days.

The 71-year-old woman was twice treated with blood plasma from recovering patients, which contained antibodies against the coronavirus. Eventually, she “cleaned up” the infection without it being clear whether the plasma treatment helped. The woman’s cure will be further studied in other immunocompromised patients with Covid-19.

It also remains questionable why she showed no symptoms, despite her weakened immune system, as these patients are at greater risk of severe Covid-19 with pneumonia. Munster spoke of a “mystery”, although he pointed out that it may be an isolated case.

The doctors also performed genetic tests on the woman during the course of the infection and found that the coronavirus showed several mutations over time, but these did not affect its ability to reproduce. Still, none of the mutations gained an advantage over the others.