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."