While the transmission of the novel coronavirus as small aerosol particles is more significant in summer, new research has found that direct contact with respiratory droplets can be worsening in the winter season.
The modelling study which is published in the journal Nano Letters, also noted that the currently followed social/physical distancing guidelines are incapable of controlling and containing the coronavirus transmission.
Yanying Zhu, a co-author of the study from the University of California (UC) Santa Barbara in the US said, “We found that in most situations, respiratory droplets travel longer distances than the 6-foot social distance recommended by the CDC.” Indoor environments such as walk-in refrigerators and coolers are riskier. At such cooler places, the temperatures are low and humidity is high to keep fresh meat and produce from losing water in storage, it is where the effect increases. The scientists said that under such temperature the droplets can transmit to distances of up to 6 metres (19.7 feet) before falling to the ground.
Thee scientist said under such atmospheric conditions, the virus stays persistent, remaining “infectious from several minutes to longer than a day in various environments. This is maybe an explanation for those super-spreading events that have been reported at multiple meat processing plants,” Zhu said.
Whereas in extreme climates, hot and dry places, the respiratory droplets can evaporate easily and the evaporated droplets leave behind tiny virus fragments that join the other aerosolized virus particles then shed as part of speaking, coughing, sneezing and breathing.
“These are very tiny particles, usually smaller than 10 microns. And they can suspend in the air for hours, so people can take in those particles by simply breathing,” said study lead author Lei Zhao. In summer the aerosol transmission may be more significant compared to droplet contact, while droplet contact can become highly dangerous in winters. “This means that depending on the local environment, people may need to adopt different adaptive measures to prevent the transmission of this disease,” Zhao said.
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The scientists have recommended following greater social distancing if the room is cool and humid, and finer masks and air filters during hot, dry weather. According to the researchers, hot and humid environments, and cold and dry ones, did not differ significantly between aerosol and droplet distribution. They believe the findings could be a useful guide for public health decision-makers in efforts to curb the spread of covid-19.
“Combined with our study, we think we can maybe provide design guidelines for the optimal filtering for facial masks,” Zhao said. He added that the research could be useful in measuring the real exposure time to the virus and amount of virus that could land on one’s body over a certain period of exposure. According to the scientists, the insights, “may shed light on the course of development of the current pandemic, when combined with systematic epidemiological studies.”