New Delhi: A new study reveals that speaking to someone while infected with Covid-19 could be just as dangerous as coughing next to them.
A study published 20 January in The Royal Society journal by Prof Pedro Magalhães de Oliveira, a fluid mechanics expert at Cambridge University, and four others found that it was unsafe to stand within two metres from an infected person without a mask. At that distance, an infected person talking is just as much of a risk to others if they were coughing.
Tiny droplets released while speaking could carry the virus over longer distances and even linger longer as compared to larger droplets emitted while coughing, which fall over short distances.
De Oliveira and others built mathematical models by taking into account the size of the droplets emitted from the individuals who were infected when they spoke or coughed, along with the composition of the droplets and the time they took to settle.
Results from their study found that it took only a few seconds for the released particles to travel more than two metres. The study further revealed that physical distancing was not enough to provide safety from Covid exposure if there was no adequate ventilation.
“You need masks, you need distancing and you need good ventilation so these particles don’t build up in an indoor space and they are safely removed,” Prof Oliveira explained.
The researchers, who were from the University of Cambridge and Imperial College London, found that an infected person speaking for 30 seconds released droplets that had much more viral mass than those released from one cough, and could remain in the air for an hour. The study further revealed that when two people were in a poorly ventilated space, with neither wearing a mask, then prolonged speaking was more likely to spread Covid than a short cough.
This is because smaller droplets are released when speaking, which spread more quickly than the droplets released while coughing, which are larger and settle on surfaces.
Calculate risk of being infected
The team also developed Airborne.cam, an online calculator for people to check their risk of getting infected with Covid through airborne particles while indoors.
Airborne.cam measures the length and height of a room, duration of time people are in the room, how ventilated it is, the rate of occupancy, the types of masks worn (if worn at all) and the activity going on in the room.
The aim of Airborne.cam is for it to be used to manage public spaces such as shops, classrooms and workplaces and to gauge whether ventilation is adequate. The calculator is already being used in several academic departments at the University of Cambridge.
However, the research cautions that the risk percentage derived should not be treated as an absolute measure as many of the model inputs are uncertain. It further stated that users should see how the risk of infection increases or decreases by wearing proper face masks and improving ventilation.
Member of the Scientific Advisory Group for Emergencies in the UK and an expert in airborne infections, Professor Catherine Noakes welcomed the study, but also cautioned that results were based on a number of assumptions.
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