Epidemiology

Covid-19 Droplets Last Longer than Previously Thought

Viruses, such as Covid-19 are known to travel in droplets of water, which can infect other people. Because of this, we know that it is more likely to get infected in the winter, rather than the summer as water condenses easier in the winter time, because the relative humidity is typically higher. It is often thought that viruses were only at risk of infecting others through large droplets since small droplets evaporate very quickly.

However, new studies conducted by the Vienna University Of Technology (TU Wien) show that water droplets of any size may pose more of a risk than we had previously thought. An article written by TU Wien says that “Due to the high humidity of the air we breathe, even small droplets can remain in the air much longer than previously assumed. The study was published in the scientific journal PNAS.”

The study, conducted by Prof. Alfredo Soldati and his team at the Institute of Fluid Mechanics and Heat Transfer TU Wien created simulations of the air that an infected human being exhales when they sneeze. The infected particles typically come in the form of liquid droplets of varying sizes, which have gas in between.

The scientists found that the droplets and the gas move together and the droplets eventually turn into gas after evaporating. However, a higher humidity could mean that it takes longer for the droplet to evaporate. 

“We found that small droplets stay in the air an order of magnitude longer than previously thought,” says Alfredo Soldati. “There’s a simple reason for this: the evaporation rate of droplets is not determined by the average relative humidity of the environment, but by the local humidity directly at the droplet’s location.” The exhaled air is much more humid than the ambient air, and this exhaled humidity causes small droplets to evaporate more slowly. When the first droplets evaporate, this locally leads to higher humidity, further slowing down the further evaporation process of other droplets.

Along with simulations and calculations, the research team also used a camera to monitor a nozzle, which would spray droplets mixed with gas, much like a sneeze. The high speed camera that they used would be able to keep track of where the droplet was discontinued and how long it stayed in the air. 

The new discoveries made about Covid-19 droplets should make us more cautious about our safety. However, it is fortunate that we have made this new discovery in a timely manner.

Source: https://scitechdaily.com/droplets-loaded-with-coronaviruses-last-far-longer-than-previously-thought/

Categories: Epidemiology