Norovirus may spread through the air rendering hospital infection measures useless

Canadian researchers said their findings mean infection control measures in hospitals could be useless. They advised that hospitals should think about new infection prevention controls, such as wearing protection around patients with the virus, or investing in machines to filter air.

The team carried out a study at eight hospitals and long-term care facilities affected by outbreaks of gastroenteritis, a common stomach bug. Norovirus causes the stomach and intestines to become inflamed, causing vomiting and diarrhoea.

For the study, Duchaine and her team gathered air samples at a distance of 1 metre from patients, at the doors to their rooms, and at nursing stations at each healthcare facility. Norovirus was found in the air at six out of eight of the hospitals. It was detected in 54% of the patients' rooms, 38% of the hallways leading to their rooms, and 50% of nursing stations.

Virus concentrations ranged from 13 to 2,350 particles per cubic meter of air. A dose of 20 norovirus particles is usually enough to cause gastroenteritis.

The study's lead author, Professor Caroline Duchaine, of Laval University, said the discovery that norovirus can spread by air could explain why outbreaks are so hard to contain.

She said: "The measures applied in hospital settings are only designed to limit direct contact with infected patients. In light of our results, these rules need to be reviewed to take into account the possibility of airborne transmission of noroviruses.

"Use of mobile air filtration units or the wearing of respiratory protection around patients with gastroenteritis are measures worth testing."

There are at least 25 different strains of noroviruses known to affect humans. Outbreaks of norovirus in public places, such as hospitals, nursing homes and schools, are common because the virus can survive for several days on surfaces or objects touched by an infected person. 

Each year, it's estimated that between 600,000 and one million people in the UK catch norovirus, and it is the most common cause of gastroenteritis.

It is also the most common cause of gastroenteritis in the US, where it causes 19-21 million illnesses and 56,000-71,000 hospitalizations a year.