According to a new study, the most important risk factor for contamination with Covid-19 is the duration of exposure to a person infected with the virus.
- 40% of people infected with Covid-19 were infected through a household contact, while these only represented 6% of contacts recorded in the application.
- Short contacts, less than 30 minutes, represent half of the contacts reported in the application but are only responsible for very few transmissions.
- The duration of exposure, more than proximity, is therefore the most important factor in the risk of contamination.
According to the latest bulletin of acute respiratory infections, published on December 27, the level of circulation of Covid-19 remains high. Thus, barrier gestures are still relevant to avoid contamination by this virus or those of winter illnesses. But which are the most effective? Social distancing might be the most important of all because, according to a study in the journal Naturethe duration of exposure to the virus would be the main factor in contamination with Covid-19.
Covid-19: duration of exposure as the main factor of contamination
To achieve this result, researchers from Pandemic Sciences Institute (PSI), Oxford Universityin the United Kingdom, analyzed the data of seven million users of the application NHS Covid-19, between April 2021 and February 2022. Users had to enter their contacts, including proximity and duration. In all, 23 million hours of exposure to the virus and 240,000 positive tests were recorded. Results: the more the duration of exposure to a person positive for Covid-19 increased, the higher the risk of contamination.
“This study shows that the duration of exposure to someone infected with Covid-19 is the main factor in indicating whether or not you will be infected, indicates Dr Luca Ferretti, researcher at PSI, author of the study, in a communicated. Many infections result from prolonged exposures. The risk of infection continues to increase with each hour spent in close proximity [d’une personne positive à la Covid-19]. Infection is not inevitable after short exposure, but the risk increases over time.”
Few Covid-19 infections with short contacts
Thus, scientists discovered that 40% of people infected with Covid-19 were infected through a household contact, while these only represented 6% of the contacts recorded in the application. Proximity therefore plays an important role, but it is above all the duration of exposure that counts. Indeed, short contacts, less than 30 minutes, represent half of the contacts reported in the application, but are only responsible for very few transmissions.
“These results show to what extent [ces] Data could be used during a future outbreak to inform social distancing precautions, indicates Professor Christophe Fraser, professor of epidemiology of infectious diseases on the PSI site and author of the study. In the case of Covid-19, this could have led to greater emphasis on the duration of contact as a transmission risk.“
But the communicated note several limitations to this study. The first is that the people who entered their data in the application may not be representative of the behavior of the rest of the population. In addition, it is possible that in the event of a positive test, users have filled in their data less correctly. Finally, the self-declaration aspect also has limits regarding the accuracy of the data.
