Coronavirus sufferers are 'most infectious up to day 5 of infection – with no risk after day 9'
PEOPLE with coronavirus are “most infectious up to day five of infection”, experts have claimed.
Researchers in the UK and Italy found that Covid-19 patients don’t pose a risk to others after day nine of infection.
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The review found that while virus shedding may be prolonged in infected individuals, the virus is usually cleared from the respiratory tract within a week of symptoms starting.
Experts at the University of Glasgow found that the duration of viral RNA (ribonucleic acid, a nucleic acid present in all living cells) detection can’t be used to determine how long a person is infectious for.
Author of the study Antonio Ho and his colleagues analysed 79 studies related to Covid and 11 on MERS.
They focused on viral shedding of the virus.
For Covid-19 the mean viral RNA shedding duration was 17 days.
This is while lower respiratory tract (LRT) infections were 14.6 days – 17.2 days when they were found in a stool sample and 16.6 days when found in serums.
The researchers said that the maximum shedding durations were 83, 59, 35 and 60 days.
None of the studies analysed by the researchers reported the isolation of the live virus after nine days and they claim that this highlights the importance of identifying cases of infection early.
They said this is key as people should isolate as soon as symptoms start – however mild.
The study comes as the UK government announced that isolation for people with symptoms would be increased from seven to 10 days.
From today, anyone who tests positive are barred from leaving their home for ten days.
Government scientists claim there is a “low, but tangible possibility that patients are infectious between seven and nine days” after they fall ill.
Key symptoms of the virus include a new and persistent cough, a high temperature and a loss of taste and smell.
Writing in medRxiv the team said: “Patients with SARS-CoV-2 infection are likely to be most infectious in the first week of illness.
“Several studies report viral load peaks during the prodromal phase of illness or at the time of symptom onset, providing a rationale for the efficient spread of SARS-CoV-2.”
They also found five studies that showed peaks in symptoms in the second week of illness.
They added that viral loads in stool samples were more inconsistent.
The researchers found that the median time to clearance of the live virus was 3.5 days in upper respiratory tract samples, while it was six days in lower respiratory tract samples.
“No live virus isolated beyond day nine of symptoms despite persistently high viral RNA loads, thus emphasising that the infectious period cannot be inferred from the duration of viral RNA detection”, they added.
“Although SARS-CoV-2 RNA shedding can be prolonged in respiratory and stool samples, the duration of a viable virus is short-lived.”
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