It may be easier to spread the influenza virus (flu) than previously thought according to new US research, which has found that simply breathing could be enough to transmit the virus to others.
It is commonly believed that the flu can be spread by exposure to droplets from an infected person's coughs or sneezes, or by touching contaminated surfaces.
However the new study, led by the University of Maryland, has found evidence to suggest that avoiding those who are coughing and sneezing as well as washing hands regularly may not be enough to avoid passing the virus on to others.
In the new study the team of researchers captured the influenza virus in exhaled breath from 142 confirmed cases of people with flu in four different situations -- during natural breathing, prompted speech, spontaneous coughing, and spontaneous sneezing.
The team then assessed the infectivity of naturally occurring influenza aerosols -- tiny droplets that stay suspended in the air for a long time -- and found that a significant number of flu patients regularly shed the infectious virus into aerosol particles that are small enough to present a risk for airborne transmission.
"We found that flu cases contaminated the air around them with infectious virus just by breathing, without coughing or sneezing," explained lead researcher Dr. Donald K. Milton, M.D., MPH, "People with flu generate infectious aerosols even when they are not coughing, and especially during the first days of illness. So when someone is coming down with influenza, they should go home and not remain in the workplace and infect others."
Co-author Sheryl Ehrman added that, "The study findings suggest that keeping surfaces clean, washing our hands all the time, and avoiding people who are coughing does not provide complete protection from getting the flu. Staying home and out of public spaces could make a difference in the spread of the influenza virus."
The team now believe that the findings could be used to develop more effective public health interventions to help prevent the spread of the virus and reduce the impact of influenza epidemics and pandemics.
In the meantime, in addition to staying home when possible, the researchers also recommend getting vaccinated, which although they note is not perfect, can reduce the number of flu cases or at least the severity of the illness.
The results can be found published online in the journal Proceedings of the National Academy of Sciences.