A British study which has just been published sheds new light on Covid-19 contamination and the risk of transmission of the virus. Explanations from Dr Gérald Kierzek, emergency doctor and medical director of TipsForWomens.
Sars-Cov-2 appeared four years ago now, and scientists continue to discover new aspects of this virus. A British study, published in the journal Nature on December 20, provides new data on the risk of transmission of Covid-19.
23 million hours of exposure to the virus scrutinized
For their study, scientists from the Pandemic Sciences Institute (PSI) at the University of Oxford analyzed data from 7 million users of the NHS Covid-19 application, between April 2021 and February 2022. This represents a total of 23 million hours of exposure to the virus and 240,000 positive tests taken into account. This data was centralized by researchers in order to estimate the risks of transmission of the virus from a sick person to a healthy person based on their proximity, duration of contact and contagiousness.
40% of contaminations are caused by relatives
The lessons learned from this work may be surprising: 40% of the people studied caught Covid-19 from a loved one, while they only represent 6% of the contacts recorded in the application. Contacts lasting less than thirty minutes represent half of those reported but very rarely result in transmission of the virus.
The researchers conclude that the duration of exposure increases the risk more than proximity to a sick person. According to one of the authors of this work, Dr Luca Ferretti, researcher at PSI: “Many infections result from prolonged exposures. The risk of infection continues to increase with each hour spent in close proximity.” of a sick person.
45 minutes is enough for contamination
More precisely, infectious disease specialist Benjamin Davido estimates on FranceInfo that the “median” of Covid-19 contaminations is “three-quarters of an hour” and that “eight out of ten Covid contaminations come from exposure of more than an hour to an infected person”.
Results which can shed light on the management of a future pandemic, estimates Professor Christophe Fraser, principal investigator of the study and professor of epidemiology of infectious diseases on the PSI site: “These results show how good data could be used during a future outbreak to inform social distancing precautions. In the case of Covid-19, this could have led to greater emphasis on the duration of contact as a risk of transmission“.
A new vision of virus contamination
Asked about these results, Dr. Gérald Kierzek, emergency physician and medical director of TipsForWomens, believes that these conclusions are rather reassuring. “This study shows that contamination with the virus is not immediate, but that it takes a certain amount of contact time before becoming infected.” the doctor first explains. “This also shows to what extent the measures taken at the start, such as confinement for example, were counterproductive and anxiety-provoking. 40% of contaminations took place by relatives: instead of remaining locked up, we would have done better to advise for people to get out into the fresh air”.
Gérald Kierzek also takes the opportunity to remind us of the importance of leaving the house, getting some fresh air and that wearing a mask in these conditions is of no use. “Reduced contact time with a sick person, outdoors, will not cause you to catch the virus. he again rightly emphasizes. “On the other hand, The mask is useful to avoid contaminating others, in poorly ventilated enclosed spaces.. A question of common sense, ultimately.