January 10, 2011
Coughs And Sneezes Go The Distance
Little is known about the distances a cough or sneeze can travel, but researchers in Singapore are attempting to find out how airborne transmission of flu viruses takes place using a giant mirror and a high-speed camera.
"It's really to inform infection control teams, because there is controversy now about which pathogens, e.g. flu, 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 according to Reuters.
While it is likely a flu sufferer can infect others by coughing or sneezing, are flu viruses transmitted whilst airborne? And what about sneezing, coughing or even laughing? Previous infection control guidelines are mostly based on modeling studies and expert estimates, not hard scientific data.
In their S$1.08 million ($833,000 USD) study, funded by the National Medical Research Council of Singapore, Tang and 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.
From images seen so far, whistling and laughing appear to spread infection very effectively.
"However, whether they will lead to infection and disease depends on many other factors, such as virus survival and host immune responses - which other teams are studying."
Using volunteers, Tang and his colleagues will study the velocity and distance of exhaled airflows, or plumes, produced by coughs and sneezes, and even laughing, crying, singing, whistling, talking, snoring and breathing. "We will be studying these other forms of plumes, where possible, as all forms of exhaled jets have the potential to carry infectious agents over greater distances," Tang said.
They will evaluate interventions such as coughing into a loosely clenched fist, a tissue and different types of face masks to see how effective they are in containing airflows.
"What people do every day, we can visualize in real-time. Studying intervention is very important because we want to know how effective they are," Tang said. "This may have budgetary implications when planning for the next pandemic."
Scientists hope to make improved recommendations for infection control with better knowledge of airflows, such as how far apart to place hospital beds and quarantine measures to be taken in a place found to be housing a person with an airborne infection, such as measles, flu and drug-resistant tuberculosis.
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