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 suggests.
Currently, people are asked to keep a distance of two metres (6.8ft) when out in the community and many supermarkets have now stuck lines of tape to the floor to ensure adequate separation.
But a new analysis by the Massachusetts Institute of Technology (MIT) in the US has found that viral droplets expelled in coughs and sneezes can travel in a moist, warm atmosphere at speeds of 10-30 metres (33ft-100ft) per second, creating a cloud that can span approximately 7-8 metres (23ft-27ft).
The researchers also warn 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 team believes 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 protective equipment even when they are not in 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 3ft to 6ft (1-2 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 healthcare workers caring for patients who may be infected, even if they are farther than 6ft away from a patient."
A separate study in the same journal by Chinese researchers showed that the virus can survive well in the warm, humid conditions of a swimming pool.
It was hoped that when the weather warms up that coronavirus may die away, such as happens with seasonal flu. But the new study suggests that might not happen.
Nanjing Medical University found that after one infected man visited a bath house in Huai'an, about 700km from Wuhan, eight people using the pool fell ill.
The virus appeared to survive despite the temperature of the pool being between 25C to 41C and humidity of approximately 60pc.
"Previous studies have demonstrated that the transmission rate of a virus is significantly weakened in an environment with high temperature and humidity," first author Dr Qilong Wang wrote in 'Jama Network Open'.
"However, judging from the results of this study, the transmissibility of Sars-CoV-2 showed no signs of weakening in warm and humid conditions."