Researchers analyzed data from 7 million people in England and Wales who were using the National Health Service's contact tracing application on their mobile phones, noting that it was successful in predicting people's risk of contracting the virus after being exposed to an infected person.
Data analysis shows that the duration of exposure of infected individuals is the most important factor in transmission risk.
Casual interactions with patients of less than 30 minutes represented half of the reported interactions, and most exposures were very brief, less than an hour, the study indicated.
But exposures that lead to transmission usually last hours to days.
The study, published in the journal Nature, estimated that 40 percent of those whose data was analyzed caught the coronavirus through household contact.
Luca Ferretti, the study's principal investigator, said: “We found that the length of time you've been exposed to someone with corona is the biggest factor influencing whether or not you'll get infected.”
He explained, “Many infections result from prolonged exposure. The risk of infection continues to increase with every hour you spend in close proximity to an infected person.”
The study indicated that the risks of transmission continue to increase days after exposure, meaning that the spread of the virus among family members is not a given, and can be prevented by taking necessary precautions within the home. (free)