Chinese Study Indicates Coronavirus Spread Through Air, without Physical Contact

RIO DE JANEIRO, BRAZIL – Wuhan, where the pandemic erupted, was isolated on January 23rd. The next day, 1,000 kilometers from there in the city of Canton, a man who had just arrived from Wuhan gathered his family in a restaurant. He had no symptoms but was infected with the novel coronavirus.

China’s epidemiological surveillance, which maps all the movements of those testing positive for Covid-19, found that ten people from three different families who had lunch in the restaurant that day were contaminated.

However, most had no physical contact with the man – called patient A1. Nor did he touch the same surfaces. But then, how did contagion occur? Is airborne transmission of the virus possible? Researchers and Chinese authorities have combined criminal investigation techniques and science to solve this mystery.

From the footage from the CCTV, it was found that all those infected were sitting at the three tables at the bottom of the third of the restaurant’s five floors. In the airline of a single air-conditioner. The tables with the A families — of the Covid-19 patient –, B and C were approximately one meter away from each other.

The researchers reconstructed the scene, using dolls with the temperature of the human body. And they released a marker gas that spreads in the air like the coronavirus to represent the breathing of the only one infected, patient A1.

They found that the flow of the air-conditioner, in the closed environment, infected other people. Four of patient A1’s family A tested positive in the following weeks, as well as three of the four members of family B, and two of the seven in family C.

“In this air passage, the contaminated person was probably spraying out particles while talking, and these were flying around this environment. So much so that no waiter was contaminated. And the other tables outside this aisle where the air was flowing were not contaminated either. So this study shows a very clear sign that contamination can occur through the air”, explains Natalia Pasternak from USP (University of São Paulo).

Aerosols are microparticles — very, very small — of dust, pollution, which are suspended in the air. In a cubic centimeter of air, there may be ten to twenty thousand aerosols, and the virus is even smaller. It may stick to these microparticles — which turn into transmission surfaces.

“So if a contaminated person has moved into a room that is closed and has contaminated the environment with the virus, three hours later you come in, you run the risk of getting infected,” says USP’s Paulo Artaxo.

Another study was conducted at two hospitals in Wuhan. The researchers found particles of the virus mainly in bathrooms, cafeterias, and rooms where doctors take off their protective clothing. All areas were poorly ventilated.

“Closed environments, with little ventilation, with little exchange of air with the outside environment, are where the virus is most concentrated in aerosols. It is where we need to take greater care,” says Natália Pasternak of USP.

In Japan, a number of experiments reinforce the potential for airborne infection. Using a laser beam and very sensitive cameras, scientists are able to monitor the microparticles in the air. When someone sneezes, we see the larger droplets soon dropping, but the microparticles, which are all smaller than a hundredth of a millimeter, are hovering in the air.

The same happens when two people, without masks, are talking close to each other. The micro-droplets do not disperse. Another lab simulates a closed environment with ten people. A cough releases a hundred thousand droplets. The larger ones, in blue and green, drop. Within a minute they are on the ground. But the micro-droplets, in red, are suspended in the air. Time passes. And they do not move.

But there’s a simple and affordable way to make those micro-droplets disappear. Simply open the windows, vent the environment. The Japanese test shows that when there’s a draft the microparticles are quickly blown away.

Source: G1

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