YOUR mother was right when she told you to cover your mouth when sneezing - the airborne bacteria can spread much further than you think.
Queensland scientists have developed a new technique to study how bacteria can spread up to four metres and remain live in the air for 45 minutes after a sneeze or cough.
Queensland University of Technology's laboratory director Lidia Morawska said the research was possibly one of the first to study the longevity of airborne pseudomonas aeruginosa bacteria, a multi-drug resistant germ associated with hospital-acquired infections.
"We wanted to find out how far bacteria-carrying droplets expelled by sneezes or coughs travel such distances and remain able to infect other people after such a long time," Professor Morawska said.
The research team found that the bacteria in the cough droplets from the patients decayed in two different time spans.
"As soon as cough droplets hit the air they rapidly dry out, cool and become light enough to stay airborne. They also partly degrade through contact with oxygen in the air, with larger droplets taking much longer to evaporate," she said.
"We found that the concentration of active bacteria in the dried droplets showed rapid decay with a 10-second half-life for most of the bacteria but a subset of bacteria had a half-life of more than 10 minutes."
According to Professor Morawska, this suggests some of the pseudomonas aeruginosa bacteria are resistant to rapid biological decay and thus remain viable in room air long enough to form an airborne infection risk, especially to people with respiratory problems such as patients with cystic fibrosis.
"We think this could be because droplets are produced in different parts of the respiratory tract and carry different 'loads' of bacteria.
"The larger droplets carrying bacteria take longer to evaporate which makes them more resistant to decay and able to maintain bacteria viability for extended periods."