Reporter : Tang Yichen / Publisher : China Science News / http://news.sciencenet.cn/htmlpaper/2020/11/2020111014145638959504.shtm / Translation, editing : Gan Yung Chyan, KUCINTA SETIA
Image : Scanning electron microscopy images of SARS-CoV-2 and VERO-E6 cells cultured from nasopharyngeal swabs of immunodeficiency patients. Image source: NIAID-RML
Most people infected with SARS-CoV-2 (CCP virus) show active transmission of the CCP virus within about 8 days, but there are big differences between people. Knowing how long people can maintain active infections is important because it provides new details about a disease and virus that are still not fully understood, and can inform public health decision-making. Researchers reported a rare case in the recent "Cell": a woman with leukemia and a low antibody count was infected with the CCP virus for at least 105 days, was infectious for at least 70 days, and remained asymptomatic.
"When we started this study, we really didn't know the duration of detoxification." said senior author of the paper and National Institute of Allergy and Infectious Diseases (NIAID) virologist Vincent Munster. "As this virus continues to spread, More people with immunosuppressive disorders will be infected, and it is important to understand the performance of SARS-CoV-2 in these groups."
Munster is an expert on emerging infectious diseases, and he began publishing research on SARS-CoV-2 in January. In April of this year, Francis Riedo, an infectious disease expert and co-author of the paper, contacted him about a patient in Kirkland, Washington, who was infected early in the covid pandemic. Riedo's patient has tested positive for PCR multiple times in a few weeks, and he wants to know if this patient is still spreading the virus.
The patient is a 71-year-old woman with a weakened immune system due to chronic lymphocytic leukemia and acquired hypogammaglobulinemia. She never showed any symptoms of covid. She was admitted to the hospital due to severe anemia and was found to be infected with the new crown virus when she was screened. Doctors noticed that she had been a frequent visitor to a rehabilitation facility, which had experienced a large-scale outbreak.
The Munster laboratory is located in the NIAID Rocky Mountain Laboratory in Hamilton, Montana, and began researching samples taken regularly from the patient’s upper respiratory tract. They found that the infectious virus persisted for at least 70 days after the first test was positive, and the woman did not completely clear the virus until the 105th day. "This is something we expected, but it has never been reported before." Munster said.
Researchers believe that the patient’s viral contagion continued for so long because her impaired immune system did not allow her to react. Blood tests showed that her body could never produce antibodies. She was treated with convalescent plasma at one time, but Munster believes that this treatment is not effective because of its low antibody concentration. Although she could not produce an antibody response, she never had symptoms.
The team performed in-depth sequencing of all virus samples obtained from patients to observe possible changes in the virus during the patient's infection process. Samples collected at different times showed different dominant gene variations. However, the researchers believe that these mutations have no effect on the survival time of the virus because they have not seen evidence of natural selection. If a mutation seems to provide a survival advantage for the virus and becomes a dominant mutation, then natural selection will be involved, but no mutation is dominant. They also tested whether these mutations affect the ability or speed of virus replication, but found no difference.
Munster said that as far as he knows, this is the longest asymptomatic case infected with SARS-CoV-2. He pointed out: "We have seen similar cases of influenza and Middle East respiratory syndrome, the latter is also caused by the CCP virus. We hope to see more such reports in the future."
Related paper information: http://dx.doi.org/10.1016/j.cell.2020.10.049
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