Coronavirus: Majority of patients are infected by someone not showing any symptoms

Rob Waugh
·3-min read
Midsection of female doctor helping surgeon wearing surgical glove. Medical colleagues are preparing for surgery. They are standing in emergency room.
Most people catch coronavirus from someone displaying no symptoms (Getty)

Many of us flinch when we hear a cough in public, but a new Chinese study has suggested that most coronavirus patients are infected by someone showing no symptoms.

Researchers at the Shanghai Jiao Tong University School of Medicine used mathematical modelling to predict how people were catching the virus, based on data from China.

The reseachers believe that 79.7 of people catch the virus from someone who is not yet showing any symptoms, according to a pre-print manuscript on Medrxiv.

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Around four-fifths of patients will catch the virus from someone not displaying symptoms when measures to isolate infected patients are in place, the researchers said.

The researchers write, “The percentage is roughly 19.7% when there is no effective control, and can go up to 79.7% when control measures effectively reducing transmissions after symptom onsets are performed.”

The mathematical models used by the researchers showed that patients become infectious early on, rather than just before experiencing symptoms such as a cough.

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The researchers write, “The timing of presymptomatic transmission is on average 3.8 days before symptom onset. Patients are likely to become infectious in the early stage of their infections instead of just before their symptom onsets.”

The researchers caution that their conclusion may require more researcch.

The researchers write, “Our findings should be interpreted with caution. The epidemic data of COVID19 patients that describing the time and tracing details is very limited. Therefore both estimations of the incubation period and the serial interval of COVID19 have considerable uncertainty.”

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Last week, scientists unravelled some of the secrets of the new coronavirus in a breakthrough which helps to explain its rapid spread - and could lead to new drugs to treat it.

Researchers from the University of Minnesota investigated the ‘spike’ protein on the surface of SARS-CoV-2 to understand why the virus spread so rapidly.

The work could lay the groundwork for drugs to block the novel coronavirus from attaching itself to, and infecting, human cells, the researchers believe.

The study was published in the journal Nature.

During infection, researchers used X-rays to probe the ‘spike’ protein, which attaches itself to proteins in human lungs, to see how it differed from the previous, similar virus behind SARS.

The resarchers found that a molecular “ridge” in the spike protein more compact than a similar structure in the 2002–2003 virus.

This and other changes helped SARS-CoV-2 attach more strongly to the receptor, infect human cells better, and spread faster.

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