Social distancing: new study suggests two metres is not enough
People may still be at risk even when they are more than two metres away from an infected person
By
Sarah Knapton,
SCIENCE EDITOR
27 March 2020 • 7:00pm
The two-metre social distancing rule being used to keep people apart may need to be four times bigger to prevent coronavirus from spreading, a new study by Massachusetts Institute of Technology (MIT) suggests.
Currently, people are being asked to keep a distance of around 6ft 6in when out in the community, and many supermarkets have now stuck lines of tape to the floor to ensure adequate separation between shoppers when queuing.
But the new analysis by MIT has found that viral droplets expelled in coughs and sneezes can travel in a moist, warm atmosphere at speeds of 33ft to 100ft per second (ten metres to 100 metres), creating a cloud that can span approximately 23ft to 27ft (seven metres to eight metres).
The researchers also warned that droplets can stay suspended in the air for hours, moving along airflow patterns imposed by ventilation or climate-control systems.
Virus particles have already been found in the ventilation systems of hospital rooms of patients with coronavirus, which the MIT team believe could have been carried on "turbulent clouds" of air.
Scientists said the research had implications for both the public and healthcare workers, who may not realise they need to wear personal protective equipment (PPE) even when they are not in close proximity to an infected patient.
Writing in the Journal of the American Medical Association (Jama), the authors said that current distance guidelines may be too short. "These distances are based on estimates of range that have not considered the possible presence of a high-momentum cloud carrying the droplets long distances.
"Given the turbulent puff cloud dynamic model, recommendations for separations of three feet to six feet (one metre to two metres) may underestimate the distance, timescale, and persistence over which the cloud and its pathogenic payload travel, thus generating an underappreciated potential exposure range for a healthcare worker.
"For these and other reasons, wearing of appropriate personal protection equipment is vitally important for health care workers caring for patients who may be infected, even if they are farther than six feet away from a patient."
A separate study in the same journal by Chinese researchers also showed that the virus can survive well in the warm, humid conditions of a swimming baths
It was hoped that when the weather warms up , coronavirus might die away, which is usually what happens with seasonal flu. But the new study suggests that this might not happen.
Nanjing Medical University in China found that after one infected man visited a bath house in the town of Huai’an, about 435 miles northeast of Wuhan, eight people using the pool contracted the coronavirus in the following days.
The virus appeared to survive despite the temperature of the pool being between 25 degrees Celsius and 41 degrees Celsius and humidity of approximately 60 per cent, conditions that normally would have killed a virus like flu.
"Previous studies have demonstrated that the transmission rate of a virus is significantly weakened in an environment with high temperature and humidity," author Dr Qilong Wang wrote.
"However, judging from the results of this study, the transmissibility showed no signs of weakening in warm and humid conditions."