With COVID-19, Patients Become Infectious 2-3 Days Before Symptoms Appear

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With COVID-19, Patients Become Infectious 2-3 Days Before Symptoms Appear
With COVID-19, Patients Become Infectious 2-3 Days Before Symptoms Appear

Video: With COVID-19, Patients Become Infectious 2-3 Days Before Symptoms Appear

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With COVID-19, patients become infectious 2-3 days before symptoms appear

Scientists have calculated how often COVID-19 is transmitted by people who do not have symptoms of the disease, and on which days the infectiousness of those infected is highest.

With COVID-19, patients become infectious 2-3 days before symptoms appear
With COVID-19, patients become infectious 2-3 days before symptoms appear

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Patients with COVID-19 can begin to shed a new coronavirus and infect others two to three days before symptoms of the disease appear. This is evidenced by a study published in Nature Medicine.

One of the factors affecting the ability to effectively control infection is whether the sick person sheds the pathogen before symptoms appear. If an infected person can infect others during the incubation period, it becomes more difficult to prevent the spread of the disease.

Scientists analyzed data on how 94 patients isolated the new coronavirus in a hospital in Guangzhou, China. Throat swabs were taken for 32 days, starting on the day of onset of symptoms. The authors of the study found that the most intense shedding of viruses occurs in the early days of illness.

In parallel, scientists have modeled the profile of the contagiousness of COVID-19, based on data on 77 "pairs of disease transmission", information about which was in the public domain. "Transmission pairs" included two people with a clear link between infection: one person was likely to have infected the other.

Based on new models, the authors concluded that humans, on average, become infectious 2.3 days before symptoms appear, and that infectiousness peaks 0.7 days before the "formal onset" of the disease. According to estimates published by Nature Medicine, 44% of transmission occurs during the asymptomatic period. Human infectiousness declines rapidly during the first week of illness.

The authors note some limitations of this study: they had to rely on patients' personal memories of the time of onset of symptoms. This could lead to some inaccuracies, as people may be late in recognizing the onset of the disease.

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