Laser/imaging tech shows how Covid-19 is spread by talking

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Micro-droplets released in conversation can drift through the air and contribute to spreading coronavirus, according to researchers from Toho University in Japan. 

This was demonstrated during an experiment aired by Japanese public broadcaster NHK. The translated TV segment can be viewed in the video below. 

The team used laser beams and a high-sensitivity camera to visualise how micro-droplets as small as 0.1 micrometers wide travelled between two people having a conversation. Although the droplets didn't spread as far through the air as through a sneeze, the tiny droplets could be seen floating and lingering in the air between the two people talking. 

'Micro-droplets carry many viruses. We produce them when we talk loudly or breathe heavily. People around us inhale them, and that's how the virus spreads. We're beginning to see this risk now,' said Kazuhiro Tateda, president, Japanese Association for Infectious Disease. 

The risk of infection through micro-droplets becomes greater in a closed space with poor ventilation. In the same tv segment, a simulation - made by researchers at Kyoto Kyoto Institute of Technology - was shown, which tracked the movement of micro-droplets in an airtight room. Ten people were shown in a room about the size of a classroom. One person coughing sends around 10,000 droplets into the air - the larger droplets fall to the floor within one minute, whereas the micro-droplets continued to drift 20 minutes after the person had coughed. 

'If the air isn't flowing, the micro-droplets won't move. And since they cannot move on their own, they stay in place for some time,' said Masashai Yamamkawa, associate professor.

The video showed how opening windows significantly helps lower the number of micro-droplets - especially if there are two areas of ventilation in different parts of the room.

NHK World

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