Opening a window could cut the amount of coronavirus in a room by half, according to a new observational study of infected college students in a University of Oregon isolation dormitory.
The study posted online is small and has not yet been published in a scientific journal. But it provides real evidence for several important principles and shows that the virus can spread into the air in a room from infected people; that the more viruses they contain, the more viruses accumulate indoors; and that both natural and mechanical ventilation appear to reduce this viral pollution.
“Ventilation is one of the most important mitigation strategies we have at our disposal,” said Kevin Van Den Wymelenberg, who led the research and heads the Institute for Health in the Built Environment.
The researchers looked at 35 University of Oregon students who tested positive for the coronavirus between January and May. All students then moved to single rooms in a Covid isolation dormitory for a 10-day isolation period.
Scientists set up Petri dishes in each room and used an active air collector to capture airborne aerosols. Several times a day, they also wiped various surfaces in the room, as well as the students’ nose and mouth.
Then they used PCR or polymerase chain reaction and tested to see if the virus was present in each sample, and if so, at what concentrations.
The data confirmed that there was a clear association between the amount of virus the students carried and the viral load in the area. As the amount of virus in the students’ nose and mouth decreased during their isolation period, the amount of airborne virus also decreased.
“There was a significant correlation between the nose samples and the air samples in the room,” said Dr. Van Den Wymelenberg.
The viral loads in the rooms were on average higher when the students were symptomatic than when they were symptomatic, although the scientists emphasized that even asymptomatic students were sending out a lot of viruses. Several self-reported symptoms, including cough, have been specifically linked to higher viral loads in the area.
The researchers also calculated the mechanical ventilation rate for each room and asked students to indicate how often the windows were open. They found that in rooms where the windows were closed more than half the time, virus loads averaged about twice as much.
“Ventilation is really important, and I think we’re just beginning to see how important it is,” said Leslie Dietz, co-author and researcher on the study at the University of Oregon.
The study had several limitations, including the fact that it only included young adults and that symptoms and window dates were self-reported. The researchers also found that they did not measure how much of the virus present in the room is viable or able to infect other people.