People who are infected with coronavirus are most at risk of spreading the virus in the first week after symptoms appear, according to new research.
The findings reaffirm the importance of identifying new cases quickly, and getting them to self-isolate as soon as possible.
Analysis of people with Covid suggested that there was no live virus found in any of the samples collected nine days after symptoms began.
Highly infectious in first 5 days
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By studying people infected with Covid - most of whom were admitted to hospital - researchers were able to measure a patient’s viral load (how much virus is in their system) and viral RNA shedding - the length of time a person sheds genetic material.
Scientists also looked at the virus itself, and how long it could survive sufficiently to replicate in a lab once it was isolated.
Their findings allowed the scientists to conclude that people with Covid are most likely to be highly infectious in the first five days after symptoms appear.
A need to raise public awareness
Lead author of the study, Dr Muge Cevik, said, “This is the first systematic review and meta-analysis that has comprehensively examined and compared viral load and shedding for… three human coronaviruses.
“It provides a clear explanation for why Sars-CoV-2 spreads more efficiently than Sars-CoV and Mers-CoV and is so much more difficult to contain.
“Our findings are in line with contact tracing studies which suggest the majority of viral transmission events occur very early, and especially within the first five days after symptom onset, indicating the importance of self-isolation immediately after symptoms start.
“We also need to raise public awareness about the range of symptoms linked with the disease, including mild symptoms that may occur earlier on in the course of the infection than those that are more prominent like cough or fever.”