The stomach bug norovirus can spread through the air up to several metres from an infected person, a new study has revealed.
According to Canadian researchers, their findings meant infection control measures in hospitals could be useless.
The researchers advise that hospitals needed to consider adopting new controls against infection, such as wearing protection around patients with the virus, or investing in machines to filter air.
The team conducted a study at eight hospitals and long-term care facilities affected by outbreaks of gastroenteritis, a common stomach bug.
The researchers collected air samples, a metre away from patients, at the doors to their rooms and at nursing stations.
Norovirus was found in the air at six out of eight of the hospitals and was detected in 54 per cent of the patients' rooms, 38 per cent of the hallways leading to their rooms, and 50 per cent of nursing stations.
According to experts, hospitals needed to consider air filtration machines to stop the virus from spreading. The concentration of the virus ranged from 13 to 2,350 particles per cubic metre of air.
A dose of 20 norovirus particles is usually enough to cause gastroenteritis.
the journal Clinical Infectious Diseases has published the study.
At least 25 different strains of noroviruses are known to affect humans.
Norovirus outbreaks in public places, such as hospitals, nursing homes and schools, are common as the virus can survive for several days on surfaces or objects touched by an infected person.
It has been estimated that each year, norovirus infects between 600,000 and 1 million people in the UK which is the most common cause of gastroenteritis.
It is also the most common cause of gastroenteritis in the US, where it caused 19-21 million illnesses and 56,000-71,000 hospitalisations a year