Turns out that flu sufferers can emit small virus particles into the air at greater distances than previously thought -- at a whopping six feet, or nearly two metres.

Researchers from Wake Forest School of Medicine in North Carolina screened 94 patients with flu symptoms admitted to the emergency room or care center of Wake Forest Baptist Medical during the 2010-2011 flu season.

"Our study offers new evidence of the natural emission of influenza and may provide a better understanding of how to best protect health care providers during routine care activities," the researchers wrote in the report.

The team collected air samples from around the patients at varying distances, and also jotted down the number of times the patients coughed or sneezed, rating the severity of the symptoms.

The study authors found that 65 percent of the patients tested positive for the flu. Of this group, 43 percent released particles containing the virus into the air.

What's worse is that the sickest people released the highest levels of virus into the air.

Plus some were "super emitters," as the researchers described, emitting up to 32 times more virus particles into the air than other patients.

Findings are published in the current edition of the Journal of Infectious Diseases.