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If there is one thing we know about SARS-CoV-2, it is that its effects on people vary. A lot. As the pandemic continues, this coronavirus continues to bring new surprises.
A team of researchers and doctors has now reported the case of one woman with leukemia who had no symptoms of COVID-19 but 70 days after her first positive test, she was still losing infectious particles of SARS-CoV-2.
This finding is much longer than previous reports of hospitalized adults experiencing the spread of the infectious SARS-CoV-2 virus for up to 20 days after COVID-19 diagnosis, in addition to other reports from people who have cleared genetic material from the virus up to 63 days after the first symptoms appeared.
The new report is expected to alert doctors and public health experts alike that symptom-free people with weakened immune systems, such as cancer patients, can apparently shed the SARS-CoV-2 virus for a long time. In this case, even months.
“Although difficult to extrapolate from a single patient, our data suggests that long-term spread of the infectious virus may be a concern in some immunocompromised patients,” the research team wrote in their paper describing the case.
An estimated 3 million people in the United States suffer from some type of condition that compromises or weakens their immune systems, making them vulnerable to infection. Examples include cancer patients receiving chemotherapy and transplant patients taking immunosuppressive drugs.
“As this virus continues to spread, more people with a range of immunosuppressive disorders will become infected, and it’s important to understand how SARS-CoV-2 behaves in these populations,” said virologist and co-author Vincent Munster of the National Institute. United States of Allergy and Infectious Diseases.
Virologists like Munster would have been alert in this pandemic for a prolonged viral spread of SARS-CoV-2. It has been established that immunocompromised people can shed common seasonal coronaviruses for weeks after infection.
Middle Eastern respiratory syndrome (MERS) studies have also shown that immunocompromised people lose the virus that causes this disease up to a month after infection.
But the proportion of asymptomatic COVID-19 cases still remains unclear. The danger is that these virus carriers can easily spend their days unaware of their ability to spread the virus.
In this case, doctors detected, isolated and monitored a woman’s SARS-CoV-2 infection using diagnostic PCR tests and throat swabs. A decade ago, the 71-year-old woman was diagnosed with chronic lymphocytic leukemia (CCL), a cancer of the white blood cells that most commonly affects the elderly and progresses slowly.
She first tested positive for SARS-CoV-2 on March 2, 2020 after being hospitalized for severe anemia related to her cancer. She then tested positive for COVID-19 another 13 times and yet showed no symptoms of the disease.
Twice he received plasma from people who had recovered from COVID-19 and eventually cleared the virus from his system in mid-June.
Doctors don’t know exactly when she acquired the coronavirus, but it was most likely in a rehabilitation facility that had a major outbreak of COVID-19 in February, where the woman had stayed days earlier.
From throat swabs collected over the course of her 15-week infection, the researchers showed that the woman was losing infectious particles of SARS-CoV-2 for 70 days. Some of its genetic material was also detected up to 105 days after the first positive result.
We have to be careful here to distinguish between infectious viral particles and the results of a diagnostic test, which only detects fragments of viral RNA. Importantly, in this study, the researchers actually isolated SARS-CoV-2 from some swab samples – day 70 included – to see if the collected virus was able to replicate in lab-grown cells, which it was.
“This indicates that, most likely, the infectious virus spread by the patient would still be able to establish a productive infection in contacts after transmission,” the researchers wrote.
SARS-CoV-2 particles obtained from the woman’s throat swab and cultured in laboratory-grown cells. (NIAID-RML)
Additionally, once doctors were alerted to the woman’s case, they also quickly recognized it as an opportunity to study how SARS-CoV-2 could evolve over the course of such a long infection.
The researchers sequenced the genetic material of the virus from various samples to see how this particular SARS-CoV-2 virus changed as it circulated through the woman’s body. Several viral variants became more dominant at certain times, but turnover was high and none stalled.
Further experiments with the virus isolated in laboratory-grown cells also showed that these genetic changes did not affect the replication rate of the virus.
While these are some valuable insights, more research still needs to be done.
“Understanding the mechanism of virus persistence and eventual elimination will be essential to provide appropriate treatment and prevent transmission of SARS-CoV-2, as persistent infection and prolonged spread of infectious SARS-CoV-2 occur. more frequently, “the study authors wrote in their paper.
And yes, this is a single case study, so we can’t make any generalizations about persistent viral spread in people with other immunocompromising conditions or the efficacy of convalescent plasma as a treatment for COVID-19, the study authors warn.
It is, however, “the longest case of anyone actively infected with SARS-CoV-2 while remaining asymptomatic,” according to the medical research team. They think the woman has been contagious for so long because her compromised immune system never allowed her to mount a response.
“We’ve seen similar cases with the flu and Middle East respiratory syndrome, which is also caused by a coronavirus,” Munster said. “We expect to see more relationships like ours in the future.”
With each one, we will surely learn more about this virus, how long it persists and what we need to do to care for the most vulnerable people in our communities.
The study was published in the journal Cell.
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