With a giant mirror and high-speed camera, scientists in Singapore are trying to find out how airborne transmission of flu viruses takes place, or if it happens at all.

The equipment allows them to observe in real time a person's spray of minuscule liquid droplets when coughing, sneezing, laughing and talking, and they hope the results can be used to put together better guidelines for infection control.

"It's really to inform infection control teams, because there is controversy now about which pathogens such as influenza, are airborne and if so, how significant this route is compared to others, such as direct contact," said team leader Julian Tang, a virologist and consultant with Singapore's National University Hospital.

While it is likely a flu sufferer can infect others by coughing or sneezing, little is known about the distances a cough or sneeze travels and the volume of air - and viruses - packed into it.

Are flu viruses transmitted whilst airborne? Which is more dangerous: coughing or sneezing, or even laughing?

Infection control guidelines are mostly based on modelling studies and expert estimates, not hard scientific data.

In their $833,000 study, funded by the National Medical Research Council of Singapore, Tang and his colleagues designed a large concave mirror, akin to those used in astronomical telescopes.

Along with a camera that can capture up to 250,000 frames per second, the scientists can observe the aerosol, or spray, produced by a cough or sneeze across the mirror.