The preliminary results of the investigation by Chinese researchers were published on Friday in Emerging Infectious Diseases, a journal of the United States Centers for Disease Control and Prevention.
They add to a growing debate about how the disease is transmitted, with scientists themselves warning that the small amounts of virus they have found at this distance are not necessarily infectious.
The researchers, led by a team from the Beijing Academy of Military Medical Sciences, tested surface and air samples from an intensive care unit and a COVID-19 general service at Huoshenshan Hospital in Wuhan. They treated a total of 24 patients between February 19 and March 2.
They discovered that the virus was most concentrated on the floor of the rooms, “perhaps because of the gravity and the air flow that floats most of the virus droplets to the floor.”
Elevated levels have also been found on frequently touched surfaces such as computer mice, trash cans, bed rails and door knobs.
“In addition, half of the shoe sole samples from ICU medical staff have tested positive,” the team wrote. “Therefore, the sole of the shoes of medical personnel could function as wearers. “
The team also looked at the so-called aerosol transmission – when the droplets of the virus are so fine that they hang and stay in the air for several hours, unlike the droplets of coughing or sneezing that fall to the ground in a few seconds.
They found that virus-laden aerosols were mainly concentrated near and downstream of patients up to 13 feet – although smaller amounts were found upstream, up to eight feet.
Encouragingly, none of the hospital staff was infected, “indicating that appropriate precautions could effectively prevent the infection,” the authors wrote.
They also offered advice contrary to orthodox guidelines: “Our results suggest that home isolation of people suspected of COVID-19 may not be a good control strategy” given the levels of environmental contamination.
Aerosolization of the coronavirus is a contentious area for scientists studying it, as it is not clear how infectious the disease is in the small amounts found in ultra-fine mist.
So far, the World Health Organization has minimized the risk.
US health officials have taken a more cautious line and urged people to cover their faces when they are in public in case the virus can be transmitted by normal breathing and speech.