The broadly accepted distance of two metres (six feet) may not be enough to stop transmission of the new coronavirus , with just a light wind able to spread infected droplets between people while outdoors, according to a new study. Public health officials in many countries may need to reconsider their safety guidelines – which usually consist of social distancing and wearing a mask – after the publication on Tuesday of the research paper in the journal Physics of Fluids . Authors Talib Dbouk and Dimitris Drikakis, from the University of Nicosia in Cyprus, found two metres was a safe approximate distance in still conditions, with droplets taking about 15 seconds to fall below human waist level. However, they found that “when a person coughs, the wind speed in an open space environment significantly influences the distance that airborne disease-carrier droplets travel”. Using a computational fluid dynamics model to compare the distance travelled by human saliva droplets in different wind conditions, the researchers found droplets could reach as far away as six metres (18 feet) in five seconds at a wind speed of just 4km/h (2.5mph). At 15km/h (9.3mph), the wind can carry droplets the same distance in just 1.6 seconds. “Our findings imply that, depending on the environmental conditions, the 2-metre social distance may not suffice,” the study said, adding that further research was necessary into the influence of other parameters, such as relative humidity and temperature of the environment. The researchers also warned that shorter adults and children could be at higher risk if they were within the trajectory of droplets carrying the infection, which has killed more than 323,000 people and infected nearly 5 million around the world.