Original title: Research shows: The most contagious five days before the appearance of COVID-19 symptoms
According to the BBC website on the 20th, an extensive study shows that people are the most contagious in the first five days after they are infected with COVID-19 and have symptoms. The research results are published in the latest issue of the Lancet Microbiology. Scientists say the study shows that early isolation is crucial to stop the spread of the virus.
It is reported that the infectivity of an individual depends on many factors, including how many live viruses (the virus that can be replicated) they carry and the number of viruses in the body.
Scientists examined 79 global studies on Covid-19 that involved symptomatic infected people in hospitals. From throat samples up to nine days after the infection began, researchers were able to extract and replicate the live virus. They found that the number of viral RNA particles (fragments of genetic material from the virus) in people's throat samples peaked at the time of symptoms or within five days afterwards. Meanwhile, no active viral RNA fragments were found in nose and throat samples within an average of 17 days after symptoms began.
The researchers concluded that although these fragments are still present, most people are unlikely to be highly contagious after this because no replicable live viruses were found.
Dr. Muge Cevik of St Andrews University told the BBC that in line with other studies involving contact tracing, the findings suggest that people have the highest contagiousness early on. “It should be made sure that people are isolated as soon as possible after they have symptoms, whether mild or not. Some people may have passed the most contagious stage when they get the results of a swab,” she said.
The study did not target asymptomatic populations, but the authors warn that other studies suggest that people may also be contagious before symptoms start.
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Source: Beijing Youth Network
