NEW DELHI: Covid-19 patients can shed fragments of the virus that causes infection for up to 83 days in their respiratory or stool samples, but they are unlikely to be infectious for that long.
According to a study published in The Lancet Microbe, one of the world’s leading medical journals, no live virus has been isolated from culture of respiratory or stool sample after day nine of symptoms despite persistently high RNA loads. viral.
This means that a person affected by Covid-19 is infectious for nine days after developing symptoms of the disease, although tests can detect the presence of the virus for almost three months.
The study by researchers from the UK and Italy involved a systemic review and meta-analysis of 79 studies that focused on SARS-CoV-2, the virus that causes Covid-19.
“Most of the studies included in our review were conducted in patients admitted to hospital. Therefore, our findings may not apply to people with milder infection, although these results suggest that those with milder cases may clear the virus from their body more quickly. Furthermore, the increasing deployment of treatments, such as dexamethasone, remdesivir, and other antivirals and immunomodulators in clinical trials, is likely to influence viral shedding in hospitalized patients. More studies on viral shedding are needed in this context, ”said Dr Antonia Ho from the MRC-University of Glasgow Center for Virus Research, UK, who is one of the study authors.
The Lancet Microbe study also suggests that people infected with SARS-CoV-2 are more likely to be highly infectious from the onset of symptoms and for the next five days. So, the researchers said, it’s important to self-isolate immediately after symptoms start.
Understanding when patients are most likely to be infectious is vitally important in informing effective public health measures to control the spread of SARS-CoV-2.
The Lancet study looked at the key factors involved in this: viral load (how the amount of virus in the body changes during infection), viral RNA clearance (the amount of time someone sheds viral genetic material (RNA), which does not necessarily indicates a person is infectious, as this is not necessarily capable of replicating) and isolation of the live virus (a stronger indicator of a person’s infectivity, as the live virus is isolated and tested to see if it can replicate successfully in the laboratory).
The researchers found that the average clearance time of viral RNA in the upper respiratory tract, lower respiratory tract, feces, and serum was 17 days, 14.6 days, 17.2 days, and 16.6 days, respectively. The longest time for RNA clearance was 83, 59, 35, and 60 days, respectively.
“These findings suggest that in clinical practice, it may not be necessary to repeat the PCR test to consider that a patient is no longer infectious, as this could remain positive for much longer and does not necessarily indicate that they could transmit the virus. to others. In patients with non-severe symptoms, their period of contagion could be counted as 10 days from the onset of symptoms, ”said Dr. Muge Cevik, lead author of the study.
According to a study published in The Lancet Microbe, one of the world’s leading medical journals, no live virus has been isolated from culture of respiratory or stool sample after day nine of symptoms despite persistently high RNA loads. viral.
This means that a person affected by Covid-19 is infectious for nine days after developing symptoms of the disease, although tests can detect the presence of the virus for almost three months.
The study by researchers from the UK and Italy involved a systemic review and meta-analysis of 79 studies that focused on SARS-CoV-2, the virus that causes Covid-19.
“Most of the studies included in our review were conducted in patients admitted to hospital. Therefore, our findings may not apply to people with milder infection, although these results suggest that those with milder cases may clear the virus from their body more quickly. Furthermore, the increasing deployment of treatments, such as dexamethasone, remdesivir, and other antivirals and immunomodulators in clinical trials, is likely to influence viral shedding in hospitalized patients. More studies on viral shedding are needed in this context, ”said Dr Antonia Ho from the MRC-University of Glasgow Center for Virus Research, UK, who is one of the study authors.
The Lancet Microbe study also suggests that people infected with SARS-CoV-2 are more likely to be highly infectious from the onset of symptoms and for the next five days. So, the researchers said, it’s important to self-isolate immediately after symptoms start.
Understanding when patients are most likely to be infectious is vitally important in informing effective public health measures to control the spread of SARS-CoV-2.
The Lancet study looked at the key factors involved in this: viral load (how the amount of virus in the body changes during infection), viral RNA clearance (the amount of time someone sheds viral genetic material (RNA), which does not necessarily indicates a person is infectious, as this is not necessarily capable of replicating) and isolation of the live virus (a stronger indicator of a person’s infectivity, as the live virus is isolated and tested to see if it can replicate successfully in the laboratory).
The researchers found that the average clearance time of viral RNA in the upper respiratory tract, lower respiratory tract, feces, and serum was 17 days, 14.6 days, 17.2 days, and 16.6 days, respectively. The longest time for RNA clearance was 83, 59, 35, and 60 days, respectively.
“These findings suggest that in clinical practice, it may not be necessary to repeat the PCR test to consider that a patient is no longer infectious, as this could remain positive for much longer and does not necessarily indicate that they could transmit the virus. to others. In patients with non-severe symptoms, their period of contagion could be counted as 10 days from the onset of symptoms, ”said Dr. Muge Cevik, lead author of the study.
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